Object‐oriented design patterns for debugging heterogeneous languages and virtual machines

Debugging multi‐language software systems requires examining and executing these systems at multiple levels of abstraction. Embedded systems, for example, often comprise a mix of assembly language device drivers and C language control code. Embedded systems increasingly utilize Java to support dynamic loading and run‐time reconfiguration. The RTEEM (Research version of the Tcl Environment for Extensible Modeling) debugger employs three design patterns in solving the problems of multi‐language embedded system debugging. The Reflective virtual machine (VM) pattern models a language‐neutral virtual machine abstraction, with language‐specific interfaces extending this abstraction. Reflection allows a debugger to inspect and control a target VM. The Chain of Responsibility is a classic pattern used to arrange language‐specific debugger command interpreters in a delegation chain. All interpreters share a single command syntax, but each interpreter adapts commands to its language abstraction by interacting with its language‐specific VM view. Composite is another classic pattern, used to combine objects into tree structures. RTEEM employs it to aggregate VM debugger chains into a hierarchy that supports uniform command syntax for debugging threads, processes, multiprocessor systems, and compositions of these entities. This paper illustrates how combining two classic design patterns with the VM abstraction as a pattern results in an architecture that is powerful and flexible in adapting to the debugging needs of heterogeneous, distributed embedded systems. Copyright © 2004 John Wiley & Sons, Ltd.     

Pulsed magnetic field excitation sensitivity of match-type electric blasting caps

This paper presents a study on energy deposition and electromagnetic compatibility of match-type electroexplosive devices (EEDs), which recently have found more usage in pulsed power environments with high electromagnetic interference (EMI) background. The sensitivity of these devices makes them dangerous to intended and unintended radiation produced by devices commonly used in pulsed power environments. Match-type EEDs have been found to be susceptible to such low levels of energy (7-8 mJ) that safe operation of these EEDs is vital when in use near devices that produce high levels of pulsed EMI. The scope of this paper is to provide an investigation that incorporates results of similar studies to provide detonation characteristics of these EEDs. The three topics included in this study are sensitivity testing, modeling of the thermodynamic heat propagation, and electromagnetic compatibility from pulsed electromagnetic radiation. The thermodynamic joule heating of the primary explosive has been modeled by a solution to the 1D heat equation. A simple pulsed generator, Marx generator with an inductive load, was used for the electromagnetic compatibility assessment of the coupled field between the pulse generator and shorted EED. The results of the electromagnetic compatibility assessment relate the resistive, inductive, and capacitive components of the pulse generator to the area of the shorted EED.     

Effect of post-homogenisation cooling rate and Mn addition on Mg2Si precipitation and hot workability of AA6060 alloys

ABSTRACT

The microstructure evolution for different post-homogenisation cooling rates and the flow stress behaviour in direct chill cast AA6060 alloys were studied. Results revealed that decreasing cooling rates reduced the flow stress owing to the precipitation of Mg₂Si and reduction of the solid solution level. Micro-alloying of Mn generated a distribution of α-Al(FeMn)Si dispersoids during the homogenisation, with the size and number density decreasing at higher homogenisation temperatures. TEM studies confirmed that the dispersoids acted as favourable nucleation sites for Mg₂Si and significantly promoted the precipitation of Mg₂Si during subsequent cooling. The high-temperature flow stress was controlled by the solid solution levels of Mg, Si, and Mn resulting from the interaction between dispersoids and Mg₂Si. The combination of the Mn addition, a low cooling rate, and a low homogenisation temperature provided the lowest flow stress, which improved the hot workability of the alloy and promoted ready dissolution of Mg₂Si during extrusion.     

Microstructure evolution during homogenization of Al–Mn–Fe–Si alloys: Modeling and experimental results

Microstructure evolution during the homogenization heat treatment of Al–Mn–Fe–Si, or AA3xxx, alloys has been investigated using a combination of modeling and experimental studies. The model is fully coupled to CALculation PHAse Diagram (CALPHAD) software and has explicitly taken into account the two different length scales for diffusion encountered in modeling the homogenization process. The model is able to predict the evolution of all the important microstructural features during homogenization, including the inhomogeneous spatial distribution of dispersoids and alloying elements in solution, the dispersoid number density and the size distribution, and the type and fraction of intergranular constituent particles. Experiments were conducted using four direct chill (DC) cast AA3xxx alloys subjected to various homogenization treatments. The resulting microstructures were then characterized using a range of characterization techniques, including optical and electron microscopy, electron micro probe analysis, field emission gun scanning electron microscopy, and electrical resistivity measurements. The model predictions have been compared with the experimental measurements to validate the model. Further, it has been demonstrated that the validated model is able to predict the effects of alloying elements (e.g. Si and Mn) on microstructure evolution. It is concluded that the model provides a time and cost effective tool in optimizing and designing industrial AA3xxx alloy chemistries and homogenization heat treatments.     

Cardiac Mapping Instrumentation for the Instantaneous Display of Endocardial and Epicardial Activation

A real-time mapping system is described that allows instant display of both endocardial and epicardial activation as monitored by an array of transmural plunge-needle electrodes in the intact in situ heart. From the total cardiac muscle mass, 768 electrograms are recorded, with a programmable feature allowing the rapid and unrestricted selection of 110 endocardial electrograms for automated analysis. An activation analyzer (consisting of parallel analog circuitry) provides an activation image in real time, while video recorders provide both raw and processed data storage with the capability of immediate slow-motion replay. The nature of the data acquisition (110 plunge needles) limits this system to the experimental arrhythmia laboratory where its chief advantage is the enabling of the multichannel recording of endo data without the complications of open heart surgery. Equally important is the ability to automatically store the endocardial activation image locked in time to the simultaneously recorded epicardial image.     

Influences of Nickel and Vanadium Impurities on Microstructure of Aluminum Alloys

In recent years, the deterioration in the available coke quality for anode production has led to increased levels of metal impurities such as nickel and vanadium in primary aluminum. There is growing concern from the industry with regard to the impact of increased Ni and V levels on the downstream properties of Al alloy products. This article presents a detailed investigation of the influences of Ni and V impurities on microstructure of three common Al alloys, i.e., AA6063, AA3102, and A356, in both as-cast and heat-treated conditions. The characterization techniques employed include scanning electron microscopy, electron backscattered diffraction, energy-dispersive x-ray spectroscopy, wavelength-dispersive spectroscopy, and transmission electron microscopy. It is shown that the phase constituents of AA6063 are not altered by Ni additions up to 0.05% or V additions up to 0.04%. Whereas there is no change in phase constituents with increasing Ni up to 0.015% for AA3102, the addition of 0.05% Ni seems to have significant influence on the microstructure. For A356, Ni additions up to 0.02% do not seem to have significant influence on the microstructure, but a new phase with significantly high Ni content is formed when the Ni impurity level is increased to 0.05%. The deep insight obtained in this work should be helpful to understand the influences of Ni and V impurities on properties of Al alloys.     

Fine-Tuning Phylogenetic Alignment and Haplogrouping of mtDNA Sequences

In this paper, we present a new algorithm for alignment and haplogroup estimation of mitochondrial DNA (mtDNA) sequences. Based on 26,011 vetted full mitogenome sequences, we refined the 5435 original haplogroup motifs of Phylotree Build 17 without changing the haplogroup nomenclature. We adapted 430 motifs (about 8%) and added 966 motifs for yet undetermined subclades. In summary, this led to an 18% increase of haplogroup defining motifs for full mitogenomes and a 30% increase for the mtDNA control region that is of interest for a variety of scientific disciplines, such as medical, population and forensic genetics. The new algorithm is implemented in the EMPOP mtDNA database and is freely accessible.     

Detection of DNA sequence variations in homo- and heterozygous samples via molecular mass measurements by electrospray ionization time-of-flight mass spectrometry

The potential of ion-pair reversed-phase high-performance liquid chromatography on-line hyphenated to electrospray ionization time-of-flight mass spectrometry for the characterization of polymerase chain reaction (PCR) amplified nucleic acids was evaluated. For that purpose, a "SNP toolbox" was constructed by cloning and PCR-mediated site-directed in vitro mutagenesis at nucleotide position (ntp) 16,519 of a sequence-verified fragment of the human mitochondrial genome (ntps 15,900-599). Confirmatory sequencing demonstrated that within the sequences of the clones one and the same base was mutated to all other bases. Using these clones or equimolar mixtures of these clones as PCR templates, 51-401-bp-long amplicons were generated, which were used to determine the upper size limits of PCR products for the unequivocal detection of sequence variations in homo- and heterozygous samples. Based on the high mass spectrometric performance of the applied time-of-flight mass spectrometer, the unequivocal genotyping of all kinds of single base exchanges in PCR amplicons from heterozygous samples with lengths up to 254 base pairs (bp) was demonstrated. Considering homozygous samples, the successful genotyping of single base substitutions in up to 401-bp-long PCR products was possible. Consequently, the described hyphenated technique represents one of the most powerful mass spectrometric genotyping assays available today.