Quasi Online Research Articles

Fast DRR generation for 2D to 3D registration on GPUs

The generation of digitally reconstructed radiographs (DRRs) is the most time consuming step on the CPU in intensity based two-dimensional x-ray to three-dimensional (CT or 3D rotational x-ray) medical image registration, which has application in several image guided interventions. This work presents optimized DRR rendering on graphical processor units (GPUs) and compares performance achievable on four commercially available devices. A ray-cast based DRR rendering was implemented for a 512 × 512 × 72 CT volume. The block size parameter was optimized for four different GPUs for a region of interest (ROI) of 400 × 225 pixels with different sampling ratios (1.1%-9.1% and 100%). Performance was statistically evaluated and compared for the four GPUs. The method and the block size dependence were validated on the latest GPU for several parameter settings with a public gold standard dataset (512 × 512 × 825 CT) for registration purposes. Depending on the GPU, the full ROI is rendered in 2.7-5.2 ms. If sampling ratio of 1.1%-9.1% is applied, execution time is in the range of 0.3-7.3 ms. On all GPUs, the mean of the execution time increased linearly with respect to the number of pixels if sampling was used. The presented results outperform other results from the literature. This indicates that automatic 2D to 3D registration, which typically requires a couple of hundred DRR renderings to converge, can be performed quasi on-line, in less than a second or depending on the application and hardware in less than a couple of seconds. Accordingly, a whole new field of applications is opened for image guided interventions, where the registration is continuously performed to match the real-time x-ray.

SEM/EDX: Advanced investigation of structured fire residues and residue formation

Heterogeneous, gradual or structured morphology of fire residues plays an important role in fire retardancy of polymers. A scanning electron microscope with an attached energy dispersive X-ray spectrometer (SEM/EDX) is highlighted as a powerful tool for the advanced characterization of such complex fire residues, since it offers high resolution in combination with both good depth of field and analysis of chemical composition. Two examples are presented: First, comprehensive SEM/EDX investigation on a complex structured fire residue of glass fibre reinforced polyamide 6,6 (PA 66-GF) flame retarded by diethylaluminium phosphinate, melamine polyphosphate and some zinc borate. A multilayered surface crust (thickness ∼ 24 μm) covers a rather hollow area stabilized by GF glued together. The resulting efficient thermal insulation results in self-extinguishing before pyrolysis is completed, even under forced-flaming combustion. Second, sophisticated, quasi online SEM/EDX imaging of the formation of residual protection layer in layered silicate epoxy resin nanocomposites (LSEC). Burning specimens were quenched in liquid nitrogen for subsequent analyses. Different zones were distinguished in the condensed phase characterized by distinct processes such as melting and ablation of organic material, as well as agglomeration, depletion, exfoliation and reorientation of the LS.

Inadvertent Melting of Radioactive Sources in BOF or EAF: Distribution of Nuclides, Monitoring, Prevention

This report lists the relevant nuclides presently or formerly in use as radiation sources and gives an account of their expected distribution between steel melt, slag, dust and off-gas upon inadvertent meltdown. Three groups of nuclides are identified, namely (a) strong γ-emitters (Co 60, Kr 85, Cs 137, Ir 192), (b) weak γ-emitters (Ra 226, Am 241), and (c) β- and α-emitters (Ni 63, Sr 90, Pm 147, Pu 238/239, and Cm 244). Equilibrium distributions based on thermodynamic calculations and experimental investigations are presented.Combining the equilibrium partition ratios with process-specific effects leads to realistic distribution ratios: The steel melt is expected to contain about 98% of the radioactive Co, Ni, and Ir, while the dust will contain practically all the Cs and about 1% of all the other nuclides except Kr which should completely pass to the off-gas. The slag is expected to contain about 99% of the nuclides Sr, Pm, Ra, Am, Pu and Cm, and about 1% of Co, Ni and Ir dissolved in the suspended metal granules.The strongly γ-emitting nuclides can be, and are increasingly, monitored quasi on-line on steel samples taken in the meltshop and, with respect to Cs, in the baghouse. The respective equipment operates reliably and efficiently. An on-line detection of weak γ-emitters and of α- and β-emitters is technically not possible at present. The steelworks can minimize the risks connected to the inadvertent melt-down of a radioactive γ-source by introducing three consecutive steps of measures: Prevention by inspection of incoming materials; Inhouse Scrap Monitoring by inspection during transport, and finally Product Control by monitoring of steel samples and in the bag-house.

The flight experiment ANITA—a high performance air analyser for manned space cabins

Analysing Interferometer for Ambient Air (ANITA) is a flight experiment as precursor for a permanent continuous trace gas monitoring system on the International Space Station (ISS). For over 10 years, under various ESA contracts the flight experiment was defined, designed, breadboarded and set up. For the safety of the crew, ANITA can detect and quantify quasi on-line and simultaneously 32 trace gases with ppm or sub-ppm detection limits. The self-standing measurement system is based on Fourier Transform Infrared Spectrometer (FTIR) technology. The system represents a versatile air monitor allowing for the first time the detection and monitoring of trace gas dynamics of a spacecraft atmosphere. It is envisaged to accommodate ANITA in a Destiny (US LAB) Express Rack on the ISS. The transportation to the ISS is planned with the first ATV ‘Jules Verne’. The options are either the Space Shuttle or the Automated Transfer Vehicle.

Nitrous and Nitric Acid Measurements Inside and Outside of Clouds at Mt. Brocken

A measurement method for the continuous and in situ analysis of atmospheric concentration of HNO2 and HNO3 inside and outside of clouds has successfully been established. The approach for a wet effluent diffusion denuder (parallel plate design) was adopted and performed quasi on-line with an ion chromatography unit. The air flow through the denuder was 10 1/min and at 15 minutes of preconcentration we are able to record atmospheric concentrations of 15 ng/m3 of HNO2 and HNO3, respectively. Field measurements using the denuder system were done at the Mt. Brocken summit (1142 m a.s.l., Harz Mountains, Germany) in 1998 and 1999. During day-time and under clear conditions maximum values of HNO3 up to 7000 ng/m3 were observed. Measurements performed during cloud events assess first time our expectation that the comparatively very great specific droplet surface in clouds is a place for a heterogeneous HNO2 formation, after nocturnal accumulation up to 320 ng/m3 were found. Strong positive correlation between HNO2 concentrations and those of NO2 were obtained during and after cloud events to assess the origin of the observed nitrous acid. The HNO2/NO2 ratio reached 10% under humid conditions. The observed surface to volume ratios in investigated clouds were between 0.4 and 0.7. In dependence on the cloud water pH nitrite concentrations between 5–300 µg/l (1–30 ng/m3 air) were observed.

Quasi On-line Scheduling Procedures for Flexible Manufacturing Systems

Abstract This paper presents three quasi on-line scheduling procedures for FMSs consisting oi work stations, transport devices, and operators. In the scheduling different types of decisions are taken to perform a particular operation, i.e. the selection of (1) a work station, (2) a transport device and (3) an operator. Further, (4) the scheduling sequence of the operations has to be determined. The three developed procedures differ in the way these four decision problems are solved hierarchically. Several dispatching rules (SPT, SPT.TOT, SPT/TOT and EFTA) are available to solve the last mentioned decision problem. Limited buffer capacities in an FMS may cause deadlock in the procedures as well as in practice. The scheduling procedures involve a buffer handling method to avoid deadlock. A case study is presented to demonstrate the three procedures and to show some properties. Based on simulation tests, some conclusions are drawn about the performance of the scheduling procedures and the various dispatching rule.