Automatic adaptive enhancement for images obtained with fiberscopic endoscopes

Modern techniques for medical diagnostics and therapy in keyhole surgery scenarios as well as technical inspection make use of flexible endoscopes. Their characteristic bendable image conductor consists of a very limited number of coated fibers, which leads to so-called comb structure. This effect has a negative impact on further image processing steps such as feature tracking because these overlaid image structures are wrongly detected as image features. With respect to these tasks, we propose an automatic approach to generate optimal spectral filter masks for enhancement of fiberscopic images. We apply the Nyquist-Shannon sampling theorem to the spectrum of fiberscopically acquired images to obtain parameters for optimal filter mask calculation. This can be done automatically and independently of scale and resolution of the image conductor as well as type and resolution of the image sensor. We designed and verified simple rotation invariant masks as well as star-shaped rotation variant masks that contain information about orientation between the fiberscope and sensor. A subjective survey among experts between different modes of filtering certified the best results to the adapted star-shaped mask for high-quality glass fiberscopes. We furthermore define an objective metric to evaluate the results of different filter approaches, which verifies the results of the subjective survey. The proposed approach enables the automated reduction of fiberscopic comb structure. It is adaptive to arbitrary endoscope and sensor combinations. The results give the prospect of a large field of possible applications to reduce fiberscopic structure both for visual optimization in clinical environments and for further digital imaging tasks.     

Link Error Analysis and Modeling for Video Streaming Cross‐Layer Design in Mobile Communication Networks

Particularly in wireless communications, link errors severely affect the quality of the services due to the high error probability and the specific error characteristics (burst errors) in the radio access part of the network. In this work, we show that thorough analysis and appropriate modeling of radio‐link error behavior are essential to evaluate and optimize higher layer protocols and services. They are also the basis for finding network‐aware cross‐layer processing algorithms which are capable of exploiting the specific properties of the link error statistics, such as predictability. This document presents the analysis of the radio link errors based on measurements in live Universal Mobile Telecommunication System (UMTS) radio access networks as well as new link error models originating from that analysis. It is shown that the knowledge of the specific link error characteristics leads to significant improvements in the quality of streamed video by applying the proposed novel network‐ and content‐aware cross‐layer scheduling algorithms. Although based on live UMTS network experience, many of the conclusions in this work are of general validity and are not limited to UMTS only.     

UML 2.0—Neue Möglichkeiten und alte Probleme

Die inzwischen in einer stabilisierten Entwurfsfassung vorliegende Revision der weit verwendeten Unified Modeling Language (UML) zur Version 2.0 verspricht einige Neuerungen,welche die Möglichkeiten der objektorientierten Entwicklung erweitern sollen. Die Revision der Sprache setzt sich neben der Erweiterung der Ausdrucksmächtigkeit auch die Präzisionssteigerung der angebotenen graphischen Primitive zum Ziel. Der vorliegende Beitrag stellt überblicksartig die wesentlichen Neuerungen der UML 2.0 vor und beleuchtet kritisch fortdauernde Unzulänglichkeiten des Sprachansatzes. Autorenadressen siehe Beitragsende     

Microstructural characterisation of nanocrystalline GaN prepared by detonations of gallium azides

High quality nanoscale, phase-pure hexagonal gallium nitride (GaN) crystallites have been synthesized by the thermal induced detonation of molecular precursors of the type (R₃N)Ga(N₃)₃ (R=CH₃, C₂H₅, etc.). The method allows the control of the particle size regime from 2 to about 1000 nm. X-ray diffraction and Rietveld simulations revealed an anisotropic platelet-like shape of the particles. The obtained GaN material was as well characterized by transmission electron microscopy and electron diffraction, photoluminescence spectroscopy, SEM, IR, RAMAN, thermal gas effusion/mass spectrometry, thermal analysis, elemental analysis. Gas absorption measurements (BET method) showed a specific surface area of about 90 m² · g⁻¹. © 1998 John Wiley & Sons, Ltd.     

Micro Solid Oxide Fuel Cells on Glass Ceramic Substrates

Miniaturized solid oxide fuel cells are fabricated on a photostructurable glass ceramic substrate (Foturan) by thin film and micromachining techniques. The anode is a sputtered platinum film and the cathode is made of a spray pyrolysis (SP)‐deposited lanthanum strontium cobalt iron oxide (LSCF), a sputtered platinum film and platinum paste. A single‐layer of yttria‐stabilized zirconia (YSZ) made by pulsed laser deposition (PLD) and a bilayer of PLD–YSZ and SP–YSZ are used as electrolytes. The total thickness of all layers is less than 1 µm and the cell is a free‐standing membrane with a diameter up to 200 µm. The electrolyte resistance and the sum of polarization resistances of the anode and cathode are measured between 400 and 600 °C by impedance spectroscopy and direct current (DC) techniques. The contribution of the electrolyte resistance to the total cell resistance is negligible for all cells. The area‐specific polarization resistance of the electrodes decreases for different cathode materials in the order of Pt paste > sputtered Pt > LSCF. The open circuit voltages (OCVs) of the single‐layer electrolyte cells ranges from 0.91 to 0.56 V at 550 °C. No electronic leakage in the PLD–YSZ electrolyte is found by in‐plane and cross‐plane electrical conductivity measurements and the low OCV is attributed to gas leakage through pinholes in the columnar microstructure of the electrolyte. By using a bilayer electrolyte of PLD–YSZ and SP–YSZ, an OCV of 1.06 V is obtained and the maximum power density reaches 152 mW cm⁻² at 550 °C.     

Effects of a preventive cardiology curriculum on behavioral cardiovascular risk factors and knowledge of medical students

We evaluated a Preventive Cardiology Academic Award (PCAA) program designed to integrate preventive cardiology concepts into the medical school curriculum. Diet, preventive cardiology knowledge, preventive cardiology attitudes, exercise behavior, and body mass index were compared at entrance to medical school and during the graduation year. Complete data were available on 94 students (65 men and 29 women). Similar data from students who graduated in 1987, prior to the introduction of the PCAA curriculum, served as a control. Women showed a significant enhancement in attitude towards cardiovascular disease (CVD) prevention, while both men and women significantly increased their knowledge about CVD prevention. The frequency of planned physical activity decreased significantly in both sexes and men showed a significant increase in body mass index. Men significantly reduced total calories, percent of calories from fat and saturated fat and dietary cholesterol and increased fiber intake. In women, the only significant reduction was in total calories. In comparison to the control class that did not have the program, men receiving the PCAA curriculum reduced dietary cholesterol, dietary fat, saturated fat and monounsaturated fat. Changes in these dietary parameters were nonsignificant for women in comparison to the control class women. Additional analyses showed no systematic secular trends in dietary or other variables in classes entering from 1986 to 1990. We conclude that the PCAA curriculum changes have favorably affected the preventive cardiology knowledge, attitudes and diet of medical students.     

A study of the dynamics of a clapper-to-bell impact with the application of a simplified finite-element model

From an engineering point of view, church bells are structures that, during ringing, are exposed to severe loading conditions. They are damaged due to material wear, fatigue loading, material deficiencies, different clapper-to-bell layouts, ringing conditions, etc. To get an insight into the wear-related damage of bells, experimental investigations and numerical simulations of the local contact between the clapper and the bell were carried out as part of the activities of an EU-funded project called Maintenance and Protection of Bells. In order to make a full-scale comparison between the measured and simulated results a simplified model was set up. In this model the clapper was replaced by a cylinder with a rounded tip that was dropped against a block representing the bell wall. The aim of the simplified model was to study the impact phenomenon in a controlled way and to adapt the numerical model for simulating the local contact. In the article the synthesis of a finite-element model for simulating the cylinder-drop test is presented. The results of the finite-element simulations of repetitive cylinder drops are compared to the data that were measured in the laboratory. The effects of the cylinder material, the cylinder radius and the drop height of the cylinder on the local elastic–plastic behaviour of the cylinder and the block are also presented and discussed.