Design optimization of supersonic jet pumps using high fidelity flow analysis

Supersonic jet pumps are simple devices with no moving parts, where a high velocity (primary) flow is used to pump a second fluid. In this paper, Computational Fluid Dynamics (CFD) is combined with an optimization framework in order to develop a tool for the rapid generation of jet pump designs. A key feature of the problem formulation is the transformation of the jet pump design parameters in terms of geometric ratios. This approach dramatically reduces the number of unrealistic designs covered by the Design of Experiments. Optimal Latin Hypercubes for surrogate model building and model validation points are constructed using a permutation genetic algorithm and design points are evaluated using CFD. Surrogate models of primary and entrained flow rates are built using a Moving Least Squares approach. A series of optimizations for various pump sizes are performed using a genetic algorithm and Sequential Quadratic Programming, with responses calculated from the surrogates. This approach results in a set of optimized designs, from which pumps for a wide range of flow rates can be interpolated.     

The preparation and properties of some lithium zinc silicate glass-ceramics

Lithium zinc silicate glasses are of interest for the preparation of moderately high thermal expansion glass-ceramics which are suitable for sealing to a number of nickel-based superalloys. The effect of composition, in particular the variation of nucleating species, on the crystallization behaviour of a number of these glasses has been examined using differential thermal analysis, X-ray diffraction, and electron microscopy. Various crystal phases have been identified, including cristobalite, quartz, tridymite and ₀ Li₂ZnSiO₄. In addition, most of the glass-ceramics also contain an unidentified phase which may be related to the-series of lithium zinc silicates. Heat-treatment schedules have been derived on the basis of these results in order to produce a number of glass-ceramic materials. The resultant thermal expansion characteristics of the glass-ceramics have been monitored using dilatometry, and expansions in the range 12.3 to 17.1×10^–6° C^–1 (20 to 460° C), have been obtained, depending on the precise glass composition and heat-treatment schedule employed. In addition, the mechanical properties of a number of selected samples have been monitored, employing a biaxial flexure technique.     

MnS doped mesoporous silica catalysts for the generation of novel carbon nanocages

Novel MnS impregnated mesoporous silica systems have been originated for the generation of carbon nanocages. The procedure involves a simple catalytic vapour deposition (CVD) method. This is the first time that a transition metal sulfide has been used for the synthesis of carbon nanostructures.     

Acceptance diagram calculations of the performance of neutron removal mirrors

We have used the method of acceptance diagrams to compute the performance of low energy neutron removal mirrors, or “deflectors”, placed within a parallel neutron guide. Such devices are typically used to remove long wavelength neutrons from cold neutron beams. With appropriate coatings they may also be used as low energy neutron polarizers, ideally transmitting one spin state and reflecting the other spin state out of the beam. Within the small angle approximation, ignoring absorption, and representing reflectivities using unit step functions (either 0% or 100%, depending on the angle of incidence and the critical angle), the transmission probability reduces to a function of 3 ratios among 4 angles: the inclination angle of the deflector and the critical angles (which are proportional to neutron wavelength) of the upstream entrance guide, the deflector, and the guide within which the deflector is placed. The results of the acceptance diagram calculations, and of complementary ray-tracing calculations using realistic reflectivity profiles for the deflector, should benefit scientists and engineers involved in the design of neutron scattering instruments that potentially incorporate neutron deflectors.     

A comparative evaluation of halo pin designs in an immature skull model

To design an improved halo pin for use in pediatric patients, three commonly used halo pins were evaluated with a mechanical testing apparatus and segments of prepared fetal calf skull. The pins were driven through the bone segments while the load at the bone-pin interface was measured. New pins were designed with respect to pin tip and flange width and similarly compared. Mean maximum loads to penetration, normalized for bone segment thickness, were 55.6 N/mm for the PMT Corporation pin, 61.5 N/mm for the Bremer pin, and 73.6 N/mm for the Ace pin. Four new, short tipped pins were designed and compared with the Ace pin, and there was no significant difference. Finally, four new pins were designed with varying flange widths. Mean maximum loads, normalized for bone segment thickness, were 68.9 N/mm for the 4.2 mm flange, 72.2 N/mm for the 4.7 mm flange, 92.9 N/mm for the 5.2 mm flange, and 96.4 N/mm for the 5.7 mm flange. The findings of this investigation are clinically important because they may help to explain the variability in the complication rates seen with the use of different halo systems in children. The three halo pins currently on the market have different pin designs, including tip lengths and flange distances, which contribute to the difference in load to penetration for each pin. The new, wide flanged, short tipped halo pin design might decrease the complication rate of halo use in children by providing an improved capacity to resist penetration despite increased loads of application.     

Microbial dehalogenases: enzymes recruited to convert xenobiotic substrates

Ocular torsion was measured in five subjects during sinusoidal lateral tilt (amplitude 25 degrees, 0.2 Hz). The cervical contribution to ocular torsion was best visible as the difference between the signals obtained in conditions with only head tilt and conditions with whole body tilt. Contribution of the neck did not affect the slow component, but produced an anticompensatory modulation of the beating field offset by means of saccades (analogous to gaze shift). Static tilt conditions (25 degrees tilt) of the trunk only, the head only or the whole body showed similar data, although of smaller amplitude. The results from patients suffering from post-whiplash syndrome were similar to those of healthy subjects, showing large intersubject variability. The reduced tolerance to head tilt of whiplash patients restricts useful implementation of this sort of test in the clinic.