Sacral hydatidosis: value of MRI in the diagnosis

We present a case of primary hydatid disease of the sacrum. The diagnosis was made on MR imaging obtained to evaluate the spine for recurrent disc disease. The patient had previously undergone laminectomy elsewhere for L4-5 radiculopathy. Ultrasound-guided aspiration and visualisation of scolices confirmed the diagnosis. No other site of involvement was found.     

Primary dendrite distribution and disorder during directional solidification of Pb-Sb alloys

Pb-2.2 wt pct Sb and Pb-5.8 wt pct Sb alloys have been directionally solidified from a single-crystal seed with its [100] orientation parallel to the growth direction, to examine the primary dendrite distribution and disorder of the dendrite arrays. The dendrite distribution and ordering have been investigated using analysis techniques such as the Gauss-amplitude fit to the frequency distribution of nearest and higher-order spacings, minimum spanning tree (MST), Voronoi polygon, and Fourier transform (FT) of the dendrite centers. Since the arrangement of dendrites is driven by the requirement to accommodate side-branch growth along the 〈100〉 directions, the FT images of the fully developed dendrite centers contain spots which indicate this preferred alignment. A directional solidification distance of about three mushy-zone lengths is sufficient to ensure a steady-state dendritic array, in terms of reaching a constant mean primary spacing. However, local dendrite ordering continues throughout the directional solidification process. The interdendritic convection not only decreases the mean primary spacing, it also makes the dendrite array more disordered and reduces the ratio of the upper and lower spacing limits, as defined by the largest 5 pct and the smallest 5 pct of the population.     

Indentation characteristics of rapidly solidified Al-Cu-V and Al-Cu-Ti alloys

We report indentation characteristics of metallic glasses and nano-composites in Al-Cu-V as well as in Al-Cu-Ti systems. The melt spun ribbons of these alloys are employed to study the surface hardness characteristics of the specimen containing microstructural features at various length scales. The characterization of these materials has been done with the help of transmission electron microscope, scanning electron microscope and X-ray diffractometer. The surface hardness characteristics of melt spun ribbons with and without crystallization have been studied using a micro-hardness tester. We shall discuss the indentation behavior of ribbons in relation to their structures and microstructures.     

Dissipative particle dynamics simulations of liquid nanojet breakup

In this work, we use a dissipative-particle-dynamics (DPD)-based two-phase model to study the breakup of liquid nanojets. We show that the breakup of nanojets is accelerated by the presence of thermal fluctuations. Satellite drops, which are undesirable from an application viewpoint, are not observed in our simulations. We find that the presence of a repulsive wall enclosing the DPD liquid is necessary to prevent clogging of nanojets. We are able to recover the time evolution of minimum jet radius as given by prior theoretical analysis. This study shows that DPD is able to capture the thermal induced breakup phenomena at the sub-micron level. The coarse-grained nature of DPD along with its flexibility to allow for the modeling of complex fluids in combination with the results from this study show that DPD is a useful tool for sub-micron fluid flow simulations.     

Influence of surface treatments on CdSe thin films in photoelectro-chemical solar energy conversion

Photovoltaic performance of semiconductor-liquid junction solar cell using electro-codeposited thin filmn-CdSe is found to improve significantly by proper surface treatments. The solid state parameters of annealed films are calculated and compared with those of unannealed film-based cells. Chemical etching is found to improve short circuit current and fill factor whereas photoelectrochemical etching technique improves the stability of photoanode in polysulphide electrolyte. Annealing promotes incipient fusion of small crystallites, thus reducing the grain boundaries which are known to act as recombination centres for minority carriers and trapping centre for majority carriers. The conversion efficiency and stability are found to improve by chemical etching of the semiconductor layer because chemical etching pins Fermi level of CdSe photoanode and promotes exchange current density.     

Use of waste hot water in double basin solar still

A periodic analysis of a double basin solar still is presented in this paper. In this still waste hot water is fed into the lower basin at a constant rate such as is available from power stations or other industries. The effect of various parameters on the distillate output of the still is also investigated.     

p-channel quantum-well heterostructure MI3SFET

A p-channel heterostructure MISFET-like device based on a quantum well with an underlying impurity layer is discussed. The device is based on an AlGaAs/GaAs heterostructure with a recessed-gate geometry and uses Zn-diffused refractory-metal contacts. The 4100 cm²/V-s hole mobility obtained in this inverted-interface structure at 77 K is comparable to that achieved in normal-interface AlGaAs/GaAs heterostructures. Transconductance and K-factor values as high as 52 mS/mm and 140 mS/V-mm, respectively, are obtained at 77 K in p-channel FETs with 2.0-μm gate lengths and 6.0-μm source-drain spacings, representing state-of-the-art values for p-HFETs at similar dimensions     

Six-phase (multiphase) power transmission systems: A generalized investigation of the load flow problem

This paper deals with the generalized investigation of load flow problems of six-phase (multiphase) power transmission systems and presents several schemes for power flow calculations covering balanced and unbalanced network situations. Initially, the system models and algorithm for the assembly of the multi-phase bus admittance matrix are described. Equivalent single- and three-phase load flow studies are carried out employing the equivalent single- and three-phase representations of a six-phase transmission system. The procedure for phase coordinate load flow retaining the physical identities of the three-phase and six-phase elements is developed to investigate the problem of unbalances existing both in a three-phase and a six-phase portion of a composite power transmission network.The problem of obtaining effective starting solutions is also investigated and the computational requirements for various cases are quantified. The procedures developed in the paper are implemented on a sample system. Finally, the paper concludes with a discussion of the major findings and a future line of investigation.