Generalized buckling analysis of laminated plates with random material properties using stochastic finite elements

A generalized layer-wise stochastic finite element formulation is developed for the buckling analysis of both homogeneous and laminated plates with random material properties. The pre-buckled stresses are considered in the derivation of geometric stiffness matrix and the effect of variation in these stresses on the mean and coefficient of variation of buckling strength is studied. The mean buckling strength of plates under uniform stress assumption exactly matches with those reported in the literature. However, it is shown that the actual mean buckling strength of plates can be significantly different based on the pre-buckled stress analysis which depends on boundary constraints, principal material directions, aspect and thickness ratios of plates. The statistics of buckling strength is determined using a Taylor series expansion based mean centered first order perturbation technique. The stochastic finite element solutions obtained using layer-wise plate theory is also validated with analytical solutions presented in this paper. Parametric studies are conducted for different aspect ratios, ply orientations and boundary conditions.     

Quality of maize grains treated with allyl isothiocyanate stored in hermetic bags

This purpose of this study was to evaluate the quality of maize grain treated with allyl isothiocyanate (AITC) and stored under hermetic conditions. Maize grains with moisture contents of 14.8 or 17.9% wet basis (w.b.) initial moisture content were packaged in high density polyethylene bags and submitted to treatment with AITC at a concentration of 300 μL kg⁻¹. The bags were stored in controlled temperature chambers at 15, 25 or 35 °C. At 30-day intervals, for a period of 150 days, three bags were removed from the chambers and the grains were submitted to commercial classification, moisture content, bulk density, germination potential and electrical conductivity analyses. It was verified that AITC at 300 μL kg⁻¹ has no significant effect on the physiological quality of maize grains stored in hermetic bags. The microbiological analyses indicate the control of fungi and yeasts on the grains stored with 17.9% w.b. and treated with AITC. The maize grains stored with 14.8% w.b. moisture content in hermetic systems suffered no deterioration and retained their quality for a longer period than grains stored with 17.9% w.b. moisture content, independent of AITC treatment.     

TiO2–Au plasmonic nanocomposite for enhanced dye-sensitized solar cell (DSSC) performance

Anatase TiO₂ nanoparticles dressed with gold nanoparticles were synthesized by hydrothermal process by using mixed precursor and controlled conditions. Diffused Reflectance Spectra (DRS) reveal that in addition to the expected TiO₂ interband absorption below 360 nm gold surface plasmon feature occurs near 564 nm. It is shown that the dye sensitized solar cells made using TiO₂–Au plasmonic nanocomposite yield superior performance with conversion efficiency (CE) of ～6% (no light harvesting), current density (J_SC) of ～13.2 mA/cm², open circuit voltage (V_oc) of ～0.74 V and fill factor (FF) 0.61; considerably better than that with only TiO₂ nanoparticles (CE ～ 5%, J_SC ～ 12.6 mA/cm², V_oc ～ 0.70 V, FF ～ 0.56).     

Syntax optimization for and parsing of patterns

Theory and algorithm for optimization of a directed and labeled tree are presented. Their application for optimizing any finite pattern grammar represented in the form of a tree is discussed. Tree optimization leads to loss information which is essential for identification of patterns. Special technique for preserving this information has been suggested.Finally, outlines of two different algorithms for the parsing of patterns are included. The tree parser uses the optimized tree and the table-driven parser uses the optimized syntax stored in four separate tables.     

Stereo-stability and temperature induced transitions of collagen mimics

Collagenous matrix proteins present in almost every part of the vertebrate organism and in many non-vertebrates are expressed in a rich structural variety. The present communication attributes the theoretical interpretation of temperature induced transitions in collagen mimics in terms of stereochemistry, as explained by the modified Zimm and Bragg model. The results are found to be in good agreement with the experimental data as reported independently by Steven K. Holmgren, Jonthan A. Hodges and Cara L. Jenkins. The order of the values of nucleation parameter and enthalpy changes obtained theoretically, is attributed not only to the stereo-chemistry but also to the relative increase in the degree of stability of collagen mimics.     

Strong photo-response in a flip-chip nanowire p-Cu2O/n-ZnO junction

Cu(2)O nanoneedles are synthesized on a copper substrate by a simple anodization and reducing ambient annealing protocol. ZnO nanorods are grown on ITO coated glass by a low temperature chemical route. The electronic and photo-response properties of the p-Cu(2)O/n-ZnO flip-chip heterojunction are then studied and analyzed. We show that the I-V characteristic is rectifying and the junction exhibits a good photoresponse (～120% under 1 V reverse bias) under AM 1.5 (1 Sun) illumination. This nano-heterojunction photo-response is far stronger as compared to that of a pulsed laser deposited thin film p-Cu(2)O/n-ZnO heterojunction, which can be attributed to higher junction area in the former case.     

Exergy Based Parametric Analysis of a Heat Recovery Steam Generator

Increasing the performance of a Heat Recovery Steam Generator ( HRSG) through efficient utilization of energy associated with flue gases coming out of gas turbines in combined cycle power plants is finding a significant place in research. Amongst different approaches the second law analysis is well suited for finding out the loss of exergy at various locations, its type, and magnitude. Such information is of use in the design of new HRSG technologies and to reduce the inefficiencies in existing HRSGs. This paper presents the exergy analysis of the HRSG for calculating exergy losses, heat transfer and pressure losses for different physical components. Study indicates that various sub sections of heat recovery steam generator having different physical parameters like fin density, fin thickness, fin height, tube diameter and fin spacing show a noticeable effect on exergy loss minimization.     

Investigations for performance enhancement of dual pressure HRSG in gas/steam combined cycle power plants

A heat recovery steam generator (HRSG) is the vital equipment in a gas/steam combined cycle power plant (CCPP) which plays an important role in enhancing the overall performance of the plant. An HRSG is designed on the basis of the size of the gas and steam turbines used in the power plant. Therefore, the HRSG directly affects the performance of the CCPP and its optimisation based on physical design can improve the plant performance. In the present study, the plant data of the CCPP of NTPC Ltd. at Auraiya (U.P.), India, has been considered for study. A segmented finned model has been chosen as it is the preferred arrangement [Ganapathy, V. 2003. Industrial Boiler and Heat Recovery Steam Generator Design, Application and Calculation. New York: Marcel Dekker Inc.] and thermodynamic investigations have been carried out upon a dual pressure HRSG in a gas/steam CCPP from the perspective of maximum heat recovery and minimum pressure loss. The performance investigations of varying physical parameters of a dual pressure HRSG with segmented fins are useful for CCPP designers and for all those who are engaged in the area of heat recovery.     

Hydrodynamic and micellar properties of sodium alkyl benzene sulphonates

This paper provides hydrodynamic data and micellar properties of some sodium alkyl benzene sulphonates. The free energy of micellisation. as deduced from experimental data, is compared with that calculated from the structural parameters and shows that these sulphonates form spherical and ellipsiodal micelles in aqueous medium. The ease of micellisation and micelle size increases as one goes from sodium decyl to sodium hexadecyl benzene sulphonates. The solubilisation data of n-octane and ethyl benzene in aqueous sodium alkyl benzene sulphonate solutions above the cmc indicates that aliphatic hydrocarbons when solubilised reside within the micellar core whereas aromatic hydrocarbons reside in the micellar core as well as in the annular space between hydrodynamic shear surface and surface of the micellar core,     

Synthesis of Micron-sized Hexagonal and Flower-like Nanostructures of Lead Oxide (PbO2) by Anodic Oxidation of Lead

Nano-Micro Letters - Micron sized hexagon- and flower-like nanostructures of lead oxide (α-PbO2) have been synthesized by very simple and cost effective route of anodic oxidation of lead...