Effect of sequence of construction in the analysis of multistoreyed building frame

Multistoreyed building frames are analysed in a single step on the assumption that the frame is subjected to design load once the whole frame is constructed completely. In fact the dead load due to the various members and finishing items are imposed in stages as the frame is constructed storey by storey.In this paper, a model of the sequence of construction has been assumed and two multistoreyed frames of different configurations have been analysed. The results of analyses along with a comparison with conventional one step analysis have been presented. The effect of sequence of construction due to the self-weight of members has been studied and its effect on the overall design forces has also been highlighted.     

An evaluation of extraction techniques for the fractionation of copper and lead in model sediment systems

Model sediments were used to evaluate four extraction methods for fractionation of metals in sediment: 1. dilute HNO₃ (total specifically-adsorbed metal); 2. 1 M NH₄Cl (ion-exchangeable); 3. H₂O₂ (organic); 4. density separation using bromoform. The studies indicated that dilute HNO₃ could not remove all the lead from MnO₂, that intercomponent interferences prevented 100% removal by H₂O₂ and NH₄Cl, and that density separations could not separate oxide coatings from clay minerals.     

Doppler broadening measurements of the electron-positron annihilation radiation in nanocrystalline ZrO<Subscript>2</Subscript>

ZrO₂ powders have been ground by ball mill grinder to achieve the particle size down to 10 nm. Typical defects introduced during ball mill grinding have been studied by positron annihilation lifetime measurement technique and coincidence Doppler broadened positron annihilation radiation spectroscopic technique. Coincidence Doppler broadened positron annihilation spectra for ball mill ground and unground ZrO₂ samples have been analyzed by constructing ratio curve with defects free Al single crystal. Results indicate an increase of cation defects in ZrO₂ samples due to the reduction of particle size by the ball mill grinding process.     

Performance study of horizontal branch in building drainage system

Self-siphonage of traps of sanitary appliances caused by full-bore water discharge affects the performance of horizontal branches in building drainage sustems. Relationships have been established correlating flow, diameter and slope of branch pipes connected to main drainage stack for permissible loss of water seal with recourse to an experimental investigation in the laboratory on a range of wash-basins, as is usual in office buildings, with a view to developing a performance oriented design procedure. A measure has also been suggested to control development of negative pressure caused by self-siphonage.     

Extinction cross section of a dielectric strip

The problem of scattering of a plane electromagnetic wave by a dielectric strip is formulated in terms of an uncoupled system of three-part Wiener-Hopf equations by using a set of approximate boundary conditions. The resulting Wiener-Hopf problems are solved approximately for sufficiently large values of the width of the strip by using D.S. Jones' method (1964). An analytical formula is derived for the excitation cross section of the strip under consideration from which numerical values are obtained in specific situations and the results are presented graphically. The radar cross section of the strip is also computed for several special circumstances, and these are presented separately     

Ultracentrifugal studies of the degradation of a fracturing fluid polymer: Hydroxypropyl guar

Ultracentrifugal techniques have been employed to investigate the degradation of hydroxypropyl guar (HPG) solutions, and of gels formed with a delayed zirconium cross-linker, by ammonium persulphate at 90°C. Molecular weights, M, for various samples of degraded polymer were determined by sedimentation/diffusion, and an empirical relationship was established between M and the sedimentation coefficient at a single, low concentration. This enabled the straightforward determination of M as functions of persulphate concentration, cross-linker concentration, and time at temperature. It was shown that large decreases in M occur within the first hour at temperature, but that complete degradation is not achieved. It was further shown that, when a delayed zirconium cross-linker is used, degradation may be less effective when gels are formed and degraded at high shear rates.     

Active cellular preform derived from stems of jute and sticks of cane and their suitability for bulk porous Si/SiC ceramics

Stems of Jute (Corchorus capsularis L.) and sticks of Cane (Calamus rotang L.), plants of immense economic importance in the Indian subcontinent, were converted into carbonaceous perform (C-preform) maintaining the circular cylindrical shapes in lengths of 0.02–0.05 m by controlled thermal processing. Plant material precursors were characterized by analysis of elemental (C, H, N) and molecular (cellulose, hemicellulose, lignin) compositions, by determination of Bulk Density (BD) and ash content and by optical microscopy and X-ray diffractometry (XRD). C-preforms were also characterized by measurement of BD and by Scanning Electron Microscopy (SEM) and XRD. The C-preforms were further subjected to infiltration with Si-melt (1823–1923 K) under vacuum. Spontaneous infiltration and reaction yielded composite ceramics preserving the morphology of native Jute Stem (JS) and Cane Stick (CS) precursors on macro and micro scale. The materials were found to be duplex composites with Si and β-SiC as crystalline phases. The end ceramics were characterized by measurement of BD, and also by SEM and by XRD. Measured mean BD of the Si/SiC composites derived from JS and CS were 2190 Kg m⁻³ and 2250 Kg m⁻³. The respective volume fractions of large diameter (>100 μm) bulk pores were 0.134 and 0.204, in the composites derived from JS and CS. Taking into account the measured volume fraction internal pores of 0.11 and 0.149, the volume fractions of SiC were calculated to be 0.136 and 0.307 in the composites derived from JS and CS respectively, closely tallying with those calculated from the C-preform bulk densities. The cellular Si/SiC ceramics derived from JS and CS having special morphologies with long and large porous channels and oriented growth of constituent phases are likely to be suitable for devices such as high temperature insulators, catalyst support structures for gas phase reactions at elevated temperatures, molten metal filters and others.     

Label-free microelectronic PCR quantification

We present a robust and simple method for direct, label-free PCR product quantification using an integrated microelectronic sensor. The field-effect sensor can sequentially detect the intrinsic charge of multiple unprocessed PCR products and does not require sample processing or additional reagents in the PCR mixture. The sensor measures nucleic acid concentration in the PCR relevant range and specifically detects the PCR products over reagents such as Taq polymerase and nucleotide monomers. The sensor can monitor the product concentration at various stages of PCR and can generate a readout that resembles that of a real-time fluorescent measurement using an intercalating dye but without its potential inhibition artifacts. The device is mass-produced using standard semiconductor processes, can be reused for months, and integrates all sensing components directly on-chip. As such, our approach establishes a foundation for the direct integration of PCR-based in vitro biotechnologies with microelectronics.     

Nanoparticle‐enhanced light trapping in thin‐film silicon solar cells

A systematic investigation of the nanoparticle‐enhanced light trapping in thin‐film silicon solar cells is reported. The nanoparticles are fabricated by annealing a thin Ag film on the cell surface. An optimisation roadmap for the plasmon‐enhanced light‐trapping scheme for self‐assembled Ag metal nanoparticles is presented, including a comparison of rear‐located and front‐located nanoparticles, an optimisation of the precursor Ag film thickness, an investigation on different conditions of the nanoparticle dielectric environment and a combination of nanoparticles with other supplementary back‐surface reflectors. Significant photocurrent enhancements have been achieved because of high scattering and coupling efficiency of the Ag nanoparticles into the silicon device. For the optimum light‐trapping scheme, a short‐circuit current enhancement of 27% due to Ag nanoparticles is achieved, increasing to 44% for a “nanoparticle/magnesium fluoride/diffuse paint” back‐surface reflector structure. This is 6% higher compared with our previously reported plasmonic short‐circuit current enhancement of 38%. Copyright © 2011 John Wiley & Sons, Ltd.