Selection and Synthesis of Energetic Heterocyclic Compounds Suitable for Use in Insensitive Explosive and Propellant Compositions

The rationale behind developing insensitive energetic compounds (IECs) for incorporation into insensitive munition (IM) formulations (rather than the alternative approach of desensitizing higher energy but sensitive compounds) is discussed. With the aim of selecting a maximum of 2–3 IECs suitable for use in insensitive explosive and propellant compositions, a survey of the literature on IECs published in the last 20 years was carried out. From around 50 candidates, a selection was made of eight prime candidates, all heterocyclic compounds (principally monocyclic or fused‐ring bicyclic compounds of the di‐ or triazine, triazole or oxadiazole classes), which displayed explosive performance significantly better than that of the ubiquitous IEC, TATB. The criteria for inclusion of compounds in these listings are described. Screening of the eight candidate compounds against further performance criteria reduced the list to five compounds which were evaluated in detail – these were: CL‐14 (5,7‐diamino‐4,6‐dinitrobenzofuroxan), ANPZ‐i (2,5‐diamino‐3,6‐dinitropyrazine), NNHT (2‐nitrimino‐5‐nitro‐hexahydro‐1,3,5‐triazine), NTAPDO (5‐nitro‐2,4,6‐triaminopyrimidine‐1,3‐dioxide), and PANT [4‐(picrylamino)‐5‐nitro‐1,2,3‐triazole]. A detailed analysis of scale‐up issues associated with each compound was then made, including cost and availability of precursors, hazards (chemical and explosive), effluent streams, and other scale‐up issues (e.g. materials of plant construction). A further downselection using these criteria gave the present short‐list comprising three compounds (the first three listed above) and further evaluation is in progress. The results of this study, funded by UK MOD, comprise the UK contribution to a nine‐nation European research collaboration in the EUCLID Common European Priority Area 14 “Energetic Materials”, as part of a five‐year project which commenced in October 2003.     

Models of growing season weather impacts on breadmaking quality of spring wheat from producer fields in western Canada

BACKGROUND: The purpose of this study was to quantify growing season weather and wheat quality at individual producer fields to understand weather impacts and develop weather‐based models of spring wheat quality. RESULTS: Ninety‐six hard red spring wheat samples of two genotypes supplied by western Canadian producers in 2003 and 2004 underwent comprehensive analysis for breadmaking quality. For each individual field, daily rainfall, maximum and minimum air temperature were observed and used to calculate several measures of heat. Modeled water use, demand and stress were also calculated and all weather variables were accumulated over different phenological stages. Relationships between weather variables and wheat quality variables were determined by multivariate regression analysis separated into four steps, each adding more complex information into the models. There was substantial variation in weather conditions and wheat quality between years with generally higher quality and stronger dough in the warmer and drier year, 2003. The two genotypes displayed many differences in response to the environment. Prediction of wheat quality improved with increasing complexity of weather models and close to 50% of the variation in quality could be explained by multivariate models. CONCLUSIONS: Results showed that even for top‐grade milling wheat of similar protein content, significant differences exist in breadmaking quality of wheat from different farms. The improvement in r² when using modeled environmental variables indicates that crop water use and water stress are important for wheat quality. The development of Canada Western Red Spring quality prediction models for western Canada based on growing season weather shows promise. Copyright © 2008 Society of Chemical Industry     

Carbon nanotube-reinforced composites: frequency analysis theories based on the matrix stiffness

Strong and versatile carbon nanotubes are finding new applications in improving conventional polymer-based fibers and films. This paper studies the influence of matrix stiffness and the intertube radial displacements on free vibration of an individual double-walled carbon nanotube (DWNT). For this, a double elastic beam model is presented for frequency analysis in a DWNT embedded in an elastic matrix. The analysis is based on both Euler–Bernoulli and Timoshenko beam theories which considers shear deformation and rotary inertia and for both concentric and non-concentric assumptions considering intertube radial displacements and the related internal degrees of freedom. New intertube resonant frequencies and the associated non-coaxial vibrational modes are calculated. Detailed results are demonstrated for the dependence of resonant frequencies and mode shapes on the matrix stiffness. The results indicate that internal radial displacement and surrounding matrix stiffness could substantially affect resonant frequencies especially for longer double-walled carbon nanotubes of larger innermost radius at higher resonant frequencies, and thus the latter does not keep the otherwise concentric structure at ultrahigh frequencies. Therefore, depending on the matrix stiffness, for carbon nanotubes reinforced composites, different analysis techniques should be used while the aspect ratio of carbon nanotubes has a little effect on the analysis theory which should be selected.     

Effect of rare earth on physical properties of Na0.5Bi0.5TiO3 system: A density functional theory investigation

Na_0.5(Bi_3/4RE_1/4)_0.5TiO₃ (RENBT, RE = Nd, Gd, Dy, and Ho) compounds were investigated in the framework of first-principles calculations using the full potential linearized augmented plane wave (FP-LAPW) method based on the spin-polarized density functional theory implemented in the WIEN2k code. Combined charge density distribution and Ti K-edge X-ray absorption spectra reveal that the RENBT compositions with high polarization values are accompanied by a higher TiO₆ distortion, DyNBT, and NdNBT compounds. The effect of the rare-earth elements on the polarization is confirmed experimentally with the collection of the hysteresis loops. The investigation of the electronic properties of the compounds highlights the emergence of a magnetization owing to the 4f orbital effect of the rare-earth elements. Besides, the investigation of the chemical ordering shows a short-range chemical ordering for the pure composition and an increased A-site disorder for dysprosium doped NBT system. The increased disorder may speak for increased relaxor properties in the RE doped compositions.     

Influence and Optimization of Surface Roughness on Surface Integrity during Turning Using Grey Relational Analysis

Current machining studies have reported effects of prevalent and common factors, while ultra-high finish requires holistic approach to identify all factors and investigate their effects on machining of hard to machine materials. In this work, a less investigated yet important factor, roughness of the uncut surface, was studied, and its effects on the individual response, i.e., surface finish of the machined part, were found to be significant. AISI 316, which is mainly applied in strategic areas, was selected and three effective turning factors, cutting speed (A), feed rate (B), and roughness of the uncut surface (C) on three output responses including surface roughness of the machined surface (R_a), microhardness(HV), and material removal rate (MRR), were reported. Further, single response optimization of the individual output response and multi-response optimization of all the three responses were carried out. Taguchi L₉ orthogonal array based signal-to-noise (S/N) ratio method was used for individual response optimization, and grey relational analysis (GRA) was employed for multi-response optimization. Effects of the process factors on the output responses were evaluated through inclusive statistical analyses. The individual response optimization revealed that there was a considerable effect of roughness of the uncut surface on the machining performance. Results of the GRA illustrated that the speed during the cutting process and the feed rate had substantial trace on the surface integrity (indicated by R_a and HV) and production rate (indicated by MRR), while roughness of the uncut surface did not have a significant effect.     

Reactions with the arylhydrazones of some α,β-diketoesters

Treatment of the α, β-diketo-ester-α-arylhydrazones 1a–e and 2a–d with GRIGNARD reagents results in the formation of the ketocarbinols 3a–h and 4a–g , respectively. The arylhydrazones of ethyl mesoxalate 5a–e react with phenylmagnesium bromide to yield compounds 3a–e . A novel synthesis of α-arylazo-β-arylchalcones 6a–e and their reaction with hydrazines are reported. Whereas the arylhydrazones 10a, b, 2a, b, d, 13a–c and 14a–c react with piperidine and formaldehyde to yield the MANNICH bases 11a, b, 12a–c and 15a–c , compound 5a was recovered unchanged.     

DEVELOPMENT OF HIGH-PERFORMANCE HEAVY OIL HYDROCRACK1NG CATALYSTS: CHARACTERIZATION OF ATMOSPHERIC RESIDUE FEED

ABSTRACT

The characterization results of the atmospheric residue obtained from Saudi Arabian Light crude oil show the complex nature and composition of this material. The distillation results showed that about 50 percent of Arab Light crude is the atmospheric residue. The elemental analysis of the residue showed that high amount of carbon, sulfur and nitrogen is present along with heavy metals such as nickel and vanadium. The determination of hydrocarbon types by HPLC exhibited that 12% polars and 27% aromatics are present along with 6% asphaltenes. Nuclear magnetic resonance study conducted on the residue and its fraction provides a detailed composition in terms of aliphatic and aromatic nature of the residue and its fractions. The results showed that the residue contains 21% aromatic and 79% aliphatic carbon. The aliphatic carbon is present in saturates and as side chains of aromatic and polar molecules whereas the aromatic carbons are those in the ring structure. Asphaltenes separated from the residue were characterized for their different properties to understand its complexity. The use of electron spin resonance spectroscopy provides determination of the free radicals present in the residue. Asphaltenes were analyzed using the state-of-the-art high temperature high pressure electron spin resonance (ESR) technique in the temperature range 20 to 625 °C and at 30 and 50 bar hydrogen pressure. The ESR determination at 30 bar shows that me pressure was not enough to prevent the boiling of the asphaltene and thus a decrease in the spin concentration was observed beyond 350 °C temperature. The data at 50 bar pressure showed the adequacy of this pressure for ESR measurement. The PMRTA analysis of asphaltene showed a decrease in residual hydrogen with increasing temperature.     

An image registration algorithm based on phase correlation and the classical Lucas–Kanade technique

Image registration is defined as an important process in image processing in order to align two or more images. A new image registration algorithm for translated and rotated pairs of 2D images is presented in order to achieve subpixel accuracy and spend a small fraction of computation time. To achieve the accurate rotation estimation, we propose a two-step method. The first step uses the Fourier Mellin Transform and phase correlation technique to get the large rotation, then the second one uses the Fourier Mellin Transform combined with an enhance Lucas–Kanade technique to estimate the accurate rotation. For the subpixel translation estimation, the proposed algorithm suggests an improved Hanning window as a preprocessing task to reduce the noise in images then achieves a subpixel registration in two steps. The first step uses the spatial domain approach which consists of locating the peak of the cross-correlation surface, while the second uses the frequency domain approach, based on low-frequency (aliasing-free part) of aliased images. Experimental results presented in this work show that the proposed algorithm reduces the computational complexities with a better accuracy compared to other subpixel registration algorithms.