NOx emission from a two-stroke ship engine. Part 1: Modeling aspect

International Maritime Organization regulations forces ship owners to measure NO_x emission from ship engines, but standard equipped engine rooms has not installed any usable apparatus to analyze of exhaust gases. In this paper, we propose a method of NO_x emission estimation based on the measurements of working parameters of two-stroke ship engine. This estimation consists of both the model enabling to determine a temperature and model of composition of a gas mixture in the combustion chamber of the engine. Application of such model does not require carrying out direct measurements of engine exhaust gases by exhaust gas analyzers. For the developed method, results of engine working parameters should be sufficient to estimate the NO_x emission according to IMO regulations.     

Characterization of Gold—Aluminum Nitride and Gold—Silicon Carbide Interfaces

Aluminum nitride and silicon carbide substrates were screen-printed with fritless gold and fired at 850°C in air. Interfacial diffusion zones up to 7 αm thick were observed, in which the concentrations of Au, Na impurities, and combined O varied together. Secondary ion mass and photoelectron spectroscopy revealed oxidized Al in the gold conductor supported by AIN. It is suggested that enhanced oxidation accompanies the diffusion of Au into the ceramics.     

Driving force analysis in an infinite anisotropic plate with multiple crack interactions

The methodology and a rigorous solution formulation are presented for stress intesity factors (SIF's, k) and total strain energy release rates (SERR, G _T ) of a multicracked plate, that has fully interacting cracks and is subjected to a far-field arbitrary stress state. The fundamental perturbation problem is derived, and the steps needed to formulate the system of singular integral equations whose solution gives rise to the evaluation of the SIF's are identified. Parametric studies are conducted for two, three and four crack problems. The sensitivity and characteristics of the model is demonstrated.The U.S. Government right to retain a non-exclusive, royalty-free licence in and to any copyright is acknowledged.     

The formal semantics of ISO VDM-SL

This paper provides an overview of the formal semantics of VDM-SL which currently is being standardized by ISO. This is a specification language used in the formal method known as the Vienna Development Method (or simply VDM). In this paper we will focus on the foundations and the semantics of a rather unique combination of looseness and recursion.     

Evolution of the microstructure in the hot rolling process

A thermomechanical finite-element model of flat rolling is coupled with closed form equations describing the process of recrystallization and is applied to study hot rolling of low carbon steel strips. Formulae for the recrystallized grain diameters, developed by various authors, are considered. Calculated diameters of the grains are compared with the results of the measurements carried out after experimental hot rolling of the carbon steel samples. Evaluating the accuracy of the calculations, using each of the expressions for the diameter of the recrystallized austenite grains, indicates that the relation of Roberts is closest to the measurements.     

Active synthesis using the DVCCS/DVCVS

In the paper basic properties of a new versatile linear active element acting simultaneously as a Differential Voltage Controlled Current Source (DVCCS) and Differential Voltage Controlled Voltage Source (DVCVS) are described. This element called a DVCCS/DVCVS can be used for generation of all linear nondynamic elements and also can be applied directly in active RC synthesis models. The general synthesis model with one DVCCS/DVCVS element and two particular synthesis models derived from the general one are described. All synthesis models presented here allow for cascading the second degree sections without additional buffers.     

Geometric modeling of the human normal cerebral arterial system

We propose an anatomy-based approach for an efficient construction of a three-dimensional human normal cerebral arterial model from segmented and skeletonized angiographic data. The centerline-based model is used for an accurate angiographic data representation. A vascular tree is represented by tubular segments and bifurcations whose construction takes into account vascular anatomy. A bifurcation is defined quantitatively and the algorithm calculating it is given. The centerline is smoothed by means of a sliding average filter. As the vessel radius is sensitive to quality of data as well as accuracy of segmentation and skeletonization, radius outlier removal and radius regression algorithms are formulated and applied. In this way, the approach compensates for some inaccuracies introduced during segmentation and skeletonization. To create the frame of vasculature, we use two different topologies: tubular and B-subdivision based. We also propose a technique to prevent vessel twisting. The analysis of the vascular model is done on a variety of data containing 258 vascular segments and 131 bifurcations. Our approach gives acceptable results from anatomical, topological and geometrical standpoints as well as provides fast visualization and manipulation of the model. The approach is applicable for building a reference cerebrovascular atlas, developing applications for simulation and planning of interventional radiology procedures and vascular surgery, and in education.