GPU-based real-time approximation of the ablation zone for radiofrequency ablation

Percutaneous radiofrequency ablation (RFA) is becoming a standard minimally invasive clinical procedure for the treatment of liver tumors. However, planning the applicator placement such that the malignant tissue is completely destroyed, is a demanding task that requires considerable experience. In this work, we present a fast GPU-based real-time approximation of the ablation zone incorporating the cooling effect of liver vessels. Weighted distance fields of varying RF applicator types are derived from complex numerical simulations to allow a fast estimation of the ablation zone. Furthermore, the heat-sink effect of the cooling blood flow close to the applicator's electrode is estimated by means of a preprocessed thermal equilibrium representation of the liver parenchyma and blood vessels. Utilizing the graphics card, the weighted distance field incorporating the cooling blood flow is calculated using a modular shader framework, which facilitates the real-time visualization of the ablation zone in projected slice views and in volume rendering. The proposed methods are integrated in our software assistant prototype for planning RFA therapy. The software allows the physician to interactively place virtual RF applicator models. The real-time visualization of the corresponding approximated ablation zone facilitates interactive evaluation of the tumor coverage in order to optimize the applicator's placement such that all cancer cells are destroyed by the ablation.     

A methodology to specify three-dimensional interaction using Petri Nets

This work presents a methodology to formally model and to build three-dimensional interaction tasks in virtual environments using three different tools: Petri Nets, the Interaction Technique Decomposition taxonomy, and Object-Oriented techniques. User operations in the virtual environment are represented as Petri Net nodes; these nodes, when linked, represent the interaction process stages. In our methodology, places represent all the states an application can reach, transitions define the conditions to start an action, and tokens embody the data manipulated by the application. As a result of this modeling process we automatically generate the core of the application's source code. We also use a Petri Net execution library to run the application code. In order to facilitate the application modeling, we have adapted Dia, a well-known graphical diagram editor, to support Petri Nets creation and code generation. The integration of these approaches results in a modular application, based on Petri Nets formalism that allows for the specification of an interaction task and for the reuse of developed blocks in new virtual environment projects.     

Behavior change through wearables: the interplay between self-leadership and IT-based leadership

Electronic Markets - Physical inactivity is a global public health problem that poses health risks to individuals and imposes financial burdens on already strained healthcare systems. Wearables...     

Electrochemical behavior of Ni?P?SiC composite coatings: Effect of heat treatment and SiC particle incorporation

This paper describes the effects of heat treatment and of SiC particle incorporation on the electrochemical behavior and physical structure of Ni? P (17 at% P) composite coatings. The deposits were obtained by electrodeposition with various contents of SiC particles in the plating bath and heat treated at 420 °C. The physical structure was investigated by inductively coupled plasma atomic emission spectrometry (ICP‐AES), X‐ray diffraction (XRD), and scanning electron microscopy (SEM – image analysis). The electrochemical behavior of the resultant composite coatings was determined by chronopotentiometry, electrochemical impedance spectroscopy, and potentiodynamic measurements in 0.6 M NaCl solution at pH 6. Heat treatment showed a positive effect on the electrochemical behavior of Ni? P coatings, shifting the open circuit potential toward less active potentials. The incorporation of SiC particles inhibited pit nucleation on the Ni? P composite coating, with or without post‐heat treatment. However, heat treatment in the Ni? P? SiC seemed to induce cracks in the metallic matrix, initiating at the SiC particles, possibly caused by the contraction in the metallic matrix. The cracked structure promoted localized corrosion, while coatings without heat treatment resulted in a general and uniform corrosion.     

Coriolis mass flowmeters: Overview of the current state of the art and latest research

This paper is an update of the overview given by Baker RC [Coriolis flowmeters: Industrial practice and published information. Flow Meas Instrum 1994;5(4):229–46]. Overviews about mass flowmetering are also given in Baker RC [Flow measurement handbook. Cambridge University Press; 2000]. Furthermore, Drahm W and Linnartz H [Coriolis-massflowmeters: State of the art review and innovations. In: Proceedings FLUCOME 2003. 2003] reported about latest innovations in Coriolis technology.

The published information of the last decade is reviewed and the conclusions of the different papers are briefly described.     

New test method to evaluate the impact behaviour of biaxially confined concrete

A new experimental technique for imposing uniaxial or biaxial confinement on specimens subjected to dynamic load has been developed. A drop weight impact machine was used to “split” the confined specimens. Different levels of pre-stress were chosen to evaluate the change in the impact behaviour due to the confinement. The results showed that the variations in the impact energy and in the maximum impact load due to the confinement were small. To quantify the damage of the impacted specimens, a splitting tension test was performed on the already impacted specimens under quasi-static loading conditions. The values of the residual splitting tensile strength showed that the damage depends on the level of confinement. The use of such a testing method may lead to a better understanding of the impact behaviour of cementitious materials.     

Einfluss des Abstandes Emitter-Basiskontakt auf die Stromverstärkung bipolarer Transistoren

The diffusion of minority carriers from the emitter junction toward the base contact of bipolar transistors with very small dimensions cannot be neglected. The influence of this diffusion on base-current and current-amplification was demonstrated by means of analogue model-measurements. In order to calculate the diffusion toward the base contact an analytical approach is derived for the distribution of the minority carrier density between the emitter region and the base contact. There is reasonably agreement for a comparison between analytical predictions and analogue simulations for typical structures and impurity distributions.

Résumé

Chez les transistors bipolaires aux petites dimensions, la diffusion des porteurs minoritaires ne peut pas être négligée. L'influence de cette diffusion sur le courant de base et sur l'amplification du courant est démontrée par des mesures sur des modèles analogues. Une solution approximative analytique pour la distribution de la densité des porteurs minoritaires entre la région d'émetteurs et le contact de base est dérivée pour le calcul de la diffusion à la contact de base. Un assez bon rapport entre le calcul et le modèle analogue est démontré par des exemples donnés par des zones de base de géométrie typique et des différentes distributions des impurités.     

Consequences for automotive relays of a 42 VDC power network invehicles

Because of the increasing demand for electrical power in automotive vehicles the car manufacturers have decided worldwide to increase the nominal voltage of the automobile power network from 14 VDC to 42 VDC. Surveying the fundamentals of arc physics the authors show why this decision requires more extensive adaptations of the respective electromechanical switches than might be expected from a change by a factor three. Means to solve the problem are discussed     

Influence of physical/chemical characteristics of organic vaporsand gas mixtures on their contact compatibility

The formation of carbon on the contact surfaces of commercial relays by thermal decomposition of organic vapors emanating from various organic materials may cause an undesirable increase of the contact resistance in the range of several Ohms. Previous investigations revealed that the contact compatibility of an organic vapor in combination with a certain contact material depends mainly on its chemical structure. There are additional correlations between the contact compatibility on the one hand and a few parameters of the vapors like volatility, the basic structure type of the molecule (e.g., aromatic or aliphatic, length of the carbon chain), certain active groups on the other hand. The contact compatibility values of a few mixtures of organic vapors investigated corresponded to those of their individual components. Humidity and oxygen concentration of the atmosphere influenced the phenomenon effectively