NON-RANDOM DISTRIBUTION OF ADSORBATES ON CATALYTIC SURFACES: THE ROLE OF INTERACTIONS BETWEEN ADSORBATES

It has been repeatedly stressed in the literature that the commonly invoked assumption of a random distribution of adsorbates on the catalyst surface is suspect under certain operating conditions. Nonrandom distribution of the adsorbates can occur as a result of interaction between adsorbates and/or their inadequate mobility. We have studied the effect of adsorbate interactions on the rates and stability of catalytic reactions, and the salient features are outlined with several examples. An analysis of the thermodynamic data concerning the oxidation of SO₂ on platinum is presented within the framework of the proposed model.     

Determinants of software quality in offshore development - An empirical study of an Indian vendor

Context

Cost advantage has been one of the primary drivers of successful offshoring engagements of Indian software and services companies. However, the emphasis has shifted to the ability of the vendors to provide high quality over cost advantage in delivering software products and services. Meeting high quality requirements of the clients is a challenge due to the very nature of development and delivery of software through offshoring.

Objective

The objective of this research paper is to identify and evaluate the key determinants of quality in the case of software projects delivered through offshoring model.

Method

A detailed survey was conducted among project managers/project leaders (leads) of a leading midsize Indian IT services company to evaluate the relationship of the determinants on the attributes of quality.

Results

Out of six determinants, our research reveals requirements uncertainty has significant association with all the attributes of quality. While process maturity and trained personnel have moderate association, communication and control, knowledge transfer and integration and technical infrastructure have relatively low association on software quality attributes in the case of offshoring.

Conclusion

It is concluded that the complexities in offshoring necessitates proper capturing of requirements. In addition high level of process maturity and availability of trained personnel to the project will help vendors to achieve software quality. The paper provides a set of implications for practice and directions for further research.     

Direct detection and time-locked subsampling applied to pulsed electron paramagnetic resonance imaging

The application of direct time-locked subsampling (TLSS) to Fourier transform electron paramagnetic resonance (FT-EPR) spectroscopy at radio frequencies (rf) is described. With conventional FT-EPR spectroscopy, the high Larmor frequencies (L(f)) often necessitate the use of intermediate frequency (IF) stages to down convert the received free induction decay (FID) signal to a frequency that can be acquired with common data acquisition technology. However, our research focuses on in vivo studies, and consequently utilizes a FT-EPR system with a L(f) of 300 MHz. This relatively low frequency L(f), in conjunction with the advent of bandpass sampling analog-to-digital conversion and signal processing technologies, has enabled us to omit the IF stage in our FT-EPR system. With this in mind, TLSS techniques have been developed to directly sample the 300 MHz FID signal at a sampling rate of 80 MHz providing a signal bandwidth of 20 MHz. The required modifications to the data acquisition and processing system specific to this application are described. Custom software developed to control the EPR system setup, acquire the signals, and post process the data, is outlined. Data was acquired applying both coherent averaging and stochastic excitation sequences. The results of these experiments demonstrate digital down conversion of the 300 MHz FID signal to quadrature baseband. Direct FID TLSS eliminates many noise sources common in EPR systems employing traditional analog receiver techniques, such as the IF mixer stage in single channel systems, and the quadrature baseband mixer stage in dual channel systems.     

A matrix isolation FTIR investigation of laser-ablated uranium oxide in argon and nitrogen matrices

Uranium oxide was laser-ablated using the second harmonic of a Nd : YAG laser, and the products studied after trapping them in Ar and N₂ matrices. The species obtained in the Ar matrix were UO, UO₂ and UO₃, which represent the primary products of laser ablation. Charge transfer complexes, (UO ₂ ⁺ ) (O ₂ ⁻ ) and (UO ₂ ²⁺ )(O ₂ ²⁻ ) were also observed. In the N₂ matrix, in addition to the primary ablation products, reaction products with nitrogen were also observed; the prominent among them being UN₂ and NUO, together with their complexes with N₂. Charge transfer complexes were also seen in these experiments. Features due to NO, N₃ and N ₃ ⁻ were identified, which clearly point to the role of nitrogen in these reactions.     

Variant selection during nucleation and growth of γ-massive phase in TiAl-based intermetallic alloys

This work deals with the mechanisms of nucleation and growth of γ-massive phase in TiAl-based intermetallic alloys. In particular, it focuses on the process of variant selection operating at both stages of the transformation. Small γ-massive domains produced by rapid cooling are extensively characterized by high-resolution electron backscatter diffraction. This large data set allows a statistical analysis of nucleation sites, according to different crystallographic configurations. It is established that, whatever the nucleation sites, i.e., grain boundaries or triple junctions, a coherent facet is always found presenting a Blackburn orientation relationship (BOR) between the γ nucleus and the α parent grain. Moreover, some γ nuclei can additionally present another semicoherent facet with an approximate BOR with the α host grain. A new nucleation mechanism, called “co-nucleation”, is highlighted for this type of double-faceted nucleus. Variant selection during nucleation is discussed for both types of nuclei, in terms of minimization of interface energy. In addition, it is shown that growth of γ-massive domains from their initial nucleus always involves successive {1 1 1} twinning. Variant selection also occurs either at the nucleus growth stage or during the development of successive twin generations, and is discussed in terms of interphase boundary mobility.     

A new microwave processing strategy for food-ceramic composite layer confined within ceramic plates

A theoretical analysis has been carried out to study the efficient microwave processing of discrete food sample ceramic composite attached with ceramic (Al₂O₃ and SiC) plates. Continuous food sample with a specific thickness corresponding to smaller power absorption is replaced by two discrete samples and processed with ceramic composite. The effective power and temperature distribution are found to be function of discrete food sample ratios, type of microwave incidence and ceramic layer thickness. The effect of ceramic material on various discrete sample ratios have been studied via effective average power vs. thickness of ceramic (Al₂O₃ or SiC) intermediate for one side and both sides microwave incidence. It is found that power absorption is enhanced significantly for beef sample due to specific thickness of ceramic composite corresponding to one side microwave incidence. The power enhancement is lesser and the temperature difference or thermal runaway is larger for bread samples as compared to beef samples. The enhancement of heat absorption is larger for one side incidence as compared to both sides incidence with identical total intensity of microwave incidence. The role of discrete samples with ceramic composites is significant for highly lossy substances (beef) whereas the composites do not play significant role on optimal processing of low lossy substances (bread).     

High dose N ion implantation effects on surface treated UNCD films

Ion implantation is commonly used to modify the surface or near-surface properties of materials. In this work, plasma treated ultrananocrystalline diamond (UNCD) films were implanted using 100 and 200 keV high dose (10¹⁶ ions/cm²) nitrogen ions and annealed. Detailed studies have been carried out to reveal the structural and chemical states of the surface treated UNCD films before implantation, as-implanted, and after annealing by using Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and electron field emission (EFE) measurements. The high dose N ion implantation induced the formation of amorphous phase, which are converted into graphitic phase after annealing, and improved the field emission properties of UNCD films. The improved field emission is attributed to the surface charge transfer doping mechanism.     

Fluid‐particle drag in inertial polydisperse gas–solid suspensions

In this article, we extend the low Reynolds number fluid‐particle drag relation proposed by Yin and Sundaresan for polydisperse systems to include the effect of moderate fluid inertia. The proposed model captures the fluid‐particle drag results obtained from lattice‐Boltzmann simulations of bidisperse and ternary suspensions at particle mixture Reynolds numbers ranging from 0 ≤ Re_mix ≤ 40, over a particle volume fraction range of 0.2 ≤ ? ≤ 0.4, volume fraction ratios of 1 ≤ ?_i/?_j ≤ 3, and particle diameter ratios of 1 ≤ d_i/d_j ≤ 2.5. © 2009 American Institute of Chemical Engineers AIChE J, 2010     

Olfactory receptor-based polypeptide sensor for acetic acid VOC detection

Rapid detection of food-borne pathogens in packaged food products can prevent the spread of infectious diseases. This study investigates the application of novel sensing material that is sensitive to specific indicator volatile organic compound (VOC) related to Salmonella contamination in packaged meat. Specifically, the objective was to develop an olfactory receptor-based synthetic polypeptide sensor for the detecting acetic acid in low concentrations and at room temperature. Synthetic polypeptide was deposited on a quartz crystal microbalance (QCM) electrode and was evaluated for detecting acetic acid at 10–100 ppm. Developed sensor exhibited repeatable response to a particular concentration of acetic acid and displayed reproducibility among multiple sensors during acetic acid detection. Mean estimated lower detection limits of these sensors were about 1–3 ppm and linear calibration models showed linear relationships. Thus, the QCM sensors exhibited a great potential for detecting low concentrations of acetic acid at room temperature and can be used in the sensor array for packaged meat spoilage and contamination detection.