Evaluating the effect of a lightweight formal technique in industry

We evaluate the effect of applying the commercial formal technique Analytical Software Design (ASD) to an industrial project. In ASD, interfaces and software designs are modelled using a formal tabular notation. The ASD tool set supports formal checks of these models, such as deadlock freedom and interface compliance. In addition, full code can be generated from design models. ASD has been applied at Philips Healthcare to develop parts of the software of interventional X-ray systems. We report about the experiences with the embedding of ASD into the development processes. The quality of the resulting code and the productivity has been analysed and compared to code developed with other techniques. We observe that the use of ASD leads to a strong reduction of the number of defects and an increase in productivity. The results are also compared to the literature about standards and related projects at other companies.     

Identification of the regime boundaries in bubble columns based on the degree of randomness in the signals†

A new parameter (degree of randomness (DR)) was defined for the identification of the main transition velocities, U _trans. The new method reconstructs the time series into multiple state vectors, thus generating non-overlapping vector pairs and then compares the distance between them with a pre-selected cut-off length. The DR values were extracted from gauge and differential pressure fluctuations as well as x-ray tomographic scans. At every U _trans value, the DR index exhibited a well-pronounced local minimum. Three cylindrical bubble columns (BCs) with various diameters (0.1, 0.14, and 0.45 m in ID) and one rectangular BC (width = 0.2 m, depth = 0.04 m) were used. They were aerated by means of different perforated plate gas distributors. It was found that in the cylindrical BCs the disintegration of the bubbly flow regime took place always at U _trans = 0.04 m/s. In the case of the rectangular BC the first critical velocity appeared at U _trans = 0.012 m/s. The lower boundary of the churn-turbulent regime was identified at U _trans = 0.11 m/s in the smallest cylindrical BC and at about U _trans = 0.095 m/s in the other two cylindrical BCs. In the case of the rectangular BC, the second critical velocity was identified at U _trans = 0.039 m/s. The low U _trans in the rectangular BC imply that the hydrodynamic regimes are less stable in this particular column due to higher degree of liquid turbulence. The calculated DR values from the gauge pressure fluctuations successfully distinguished the upper boundary of the gas maldistribution and the first transition sub-regime.     

Viscosity of Heterogeneous Silicate Melts: A Non-Newtonian Model

The recently published viscosity data of heterogeneous silicate melts with well-documented structure and experimental conditions are critically re-analyzed and tabulated. By using these data, a non-Newtonian viscosity model incorporating solid fraction, solid shape, and shear rate is proposed on the basis of the power-law equation. This model allows calculating the viscosity of the heterogeneous silicate melts with solid fraction up to 34 vol pct. The error between the calculated and measured data is evaluated to be 32 pct, which is acceptable considering the large error in viscosity measurement of the completely liquid silicate melt.     

Closure of the concrete supercontainer in hot cell under thermal load

For the final disposal of long-lived, heat-emitting vitrified high-level waste (HLW) in a clayey host rock, an intensive study is conducted to investigate the early-age behaviour of concrete supercontainers. Self-compacting concrete (SCC) is taken as the reference concrete type as it facilitates the casting process in combination with an improved homogeneity compared to the traditional concrete compositions. A laboratory characterization program is conducted to obtain the relevant thermal, mechanical and maturity-related properties of the SCC. These obtained data are implemented into the material database of the finite element tool HEAT to study the behaviour of the concrete layers during the different construction stages of the supercontainer: (i) Stage 1: Fabrication of the concrete buffer inside a stainless steel envelope. No early-age cracking is expected in case accurate measures are taken to reduce the thermal gradient between the outer surface and the middle of the buffer, e.g. by providing insulation and excluding wind. (ii) Stages 2-4: Emplacement of the carbon steel overpack containing the HLW canisters, filling the remaining annular gap with cementitious filler and closure by fitting the lid under thermal load. The construction stages (2-4) for the closure of the supercontainer are executed in hot cell.In this study, the crack creating mechanism and the behaviour of the concrete supercontainer during these construction stages in hot cell are investigated. In case precautionary measures are taken, such as reducing the coefficient of thermal expansion (CTE) of the overpack, prolonging the preceding cooling period of the HLW or reducing the modulus of elasticity of the filler material, the formation of superficial tangential macro cracks can be prevented. In addition, the effect of elevated temperatures, due to the heat emitted by the HLW, on the strength of the hardened SCC is investigated by means of compressive strength tests and fluorescence microscopy analysis.     

System modeling methodology and analyses for materials-based hydrogen storage

In the global efforts to develop advanced materials-based hydrogen storage, the various on-board reversible hydrides, adsorbents and chemical storage candidate materials and systems each have their individual strengths and weaknesses. An overarching challenge in associated research and development is to devise material/system architectures which satisfy all requirements for viability in a particular application area, such as light-duty vehicular transportation. System modeling at the level which encompasses not only the storage material and vessel/reactor, but also integration with a fuel cell and balance-of-plant components, provides a more complete assessment of viability and guides options for improvement. The current work covers the methodology developed for conducting such system modeling consistently across multiple organizations and will present performance results from studies focused on reversible hydride systems. Connecting this high level modeling to more detailed finite element design simulations will be one aspect of our framework approach. The complex hydride NaAlH₄ is representative of novel materials under development and will be used as the basis for properties, such as temperature dependent kinetics, which influence the integrated system configurations and component sizing. While system charging is included through the sizing of certain components, emphasis is placed on hydrogen discharge by the storage system, interrogated through drive cycle transients. Comparisons of performance relative to requirements, including effective gravimetric capacity, effective volumetric density and energy utilization, are given for the baseline material and for a sensitivity study on material density.