The unsteady flow of a weakly compressible fluid in a thin porous layer. I: Two-dimensional theory

We consider the problem of determining the pressure and velocity fields for a weakly compressible fluid flowing in a two-dimensional reservoir in an inhomogeneous, anisotropic porous medium, with vertical side walls and variable upper and lower boundaries, in the presence of vertical wells injecting or extracting fluid. Numerical solution of this problem may be expensive, particularly in the case that the depth scale of the layer h is small compared to the horizontal length scale l. This is a situation which occurs frequently in the application to oil reservoir recovery. Under the assumption that epsilon=h/l<<1, we show that the pressure field varies only in the horizontal direction away from the wells (the outer region). We construct two-term asymptotic expansions in epsilon in both the inner (near the wells) and outer regions and use the asymptotic matching principle to derive analytical expressions for all significant process quantities. This approach, via the method of matched asymptotic expansions, takes advantage of the small aspect ratio of the reservoir, epsilon, at precisely the stage where full numerical computations become stiff, and also reveals the detailed structure of the dynamics of the flow, both in the neighborhood of wells and away from wells

Influence of inhomogeneity on mechanical properties of commercially pure titanium processed by HPT

Already for fifteen years many researchers have been trying to discover metallic materials with unusual combinations of strength and ductility: with high strength and enhanced ductility . This combination may be achieved through different ways: alloying, nanostructuring, etc. This report is an attempt to analyze the influence of inhomogeneity of different types (structural, phase and space) on mechanical properties of commercially pure ti tanium (bulk and powder) subjected to high- pressure torsion. Experimental results for HPT bulk and powder titanium have demonstrated that mechanical behavior of CP titanium strongly depends on phase inhomogeneity (alpha + omega phases), structural inhomoge neity (bimodal grain size distribution) and space inhomogeneity (retained porosity) in case of cold consolidated Ti powder. High strength in HPT bulk titanium due to the formation of hard omega phase during HPT processing at room temperature was detected. The strong omega phase transforms back to nanograined alpha phase domains during short annealing at elevated temperature. HPT consolidation of titanium powder leads to the formation of brittle specimens showing high strength but almost zero plasticityPeer ReviewedPostprint (author's final draft

Growth, yield and Fusarium wilt resistance of six FHIA tetraploid bananas (Musa spp.) grown in the Australian subtropics

Six tetraploid hybrids from Fundación Hondureña de Investigación Agrícola (FHIA) were evaluated in Australia over a five year period. They included three AAAA hybrids (FHIA-02, FHIA-17 and FHIA-23) and three AAAB hybrids (FHIA-01, FHIA-18 and SH-3640.10) and they were compared with industry standards, ‘Williams’ (AAA, Cavendish subgroup) and ‘Lady Finger’ (AAB, Pome subgroup). They were screened for their resistance to Fusarium wilt race 1 and subtropical race 4 caused by the pathogen Fusarium oxysporum f.sp. cubense and they were also grown for several cycles on farms not infested with Fusarium wilt to record their agronomic characteristics. The AAAB hybrids, all derived from female parent ‘Prata Anã’ (AAB, Pome subgroup) were the most resistant to both races of Fusarium wilt and were very productive in the subtropics. They were significantly more productive than ‘Lady Finger’, which was susceptible to both races of Fusarium wilt. The AAAA hybrids, with the exception of FHIA-02 which was very susceptible to Fusarium wilt and displayed the poorest agronomic traits of the six hybrids, produced bunch weights as good as Cavendish but were significantly slower to cycle. FHIA-17 and FHIA-23, both derived from the female parent ‘Highgate’ (AAA, Gros Michel subgroup), were also significantly more resistant to Fusarium wilt than ‘Gros Michel’, while FHIA-17 demonstrated a level of resistance similar to ‘Williams’ and FHIA-23 was intermediate between ‘Lady Finger’ and ‘Williams

A critical examination of pure tantalum processed by high-pressure torsion

Tantalum, a common refractory metal with body-centred cubic (BCC) crystalline structure, was processed by high-pressure torsion (HPT) at room temperature through different numbers of rotations. Significant grain refinement and high strength were achieved with a reduction in grain size from ?60 ?m to ?160 nm and an increase in strength from ?200 to &gt;1300 MPa. Hardness measurements revealed a high level of homogeneity after 10 turns of HPT but the hardness after 10 turns was slightly lower than after 5 turns indicating the occurrence of some recovery. Tensile testing at a strain rate of 1.0×10?3 s?1 gave high strengths of ?1200 MPa but little or no ductility after processing through 1, 5 and 10 turns. The introduction of a short-term (15 min) anneal immediately after HPT processing led to significant ductility in all samples and a reasonable level of strength at ?800 MPa

N-methylformamide: antitumour activity and metabolism in mice.

The antitumour activities of N-methylformamide, N-ethylformamide and formamide against a number of murine tumours in vivo (Sarcoma 180, M5076 ovarian sarcoma and TLX5 lymphoma) have been estimated. In all cases N-methyl-formamide had significant activity, formamide had marginal or no activity and N-ethylformamide had no significant activity. N-methylformamide and N-ethylformamide were equitoxic to the TLX5 lymphoma in vitro. Formamide was found as a metabolite in the plasma and urine of animals given N-methylformamide and N-ethylformamide, but excretion profiles do not support the hypothesis that formamide is an active antitumour species formed from N-alkylformamides. No appreciable metabolism of N-methylformamide occurred under a variety of conditions with liver preparations in vitro. N-methylformamide, but not N-ethylformamide or formamide, reduced liver soluble non-protein thiols by 59.8% 1 h after administration of an effective antitumour dose

Rootstock influences postharvest anthracnose development in 'Hass' avocado

Rootstock studies conducted on ‘Hass’ avocado found that rootstock had a significant impact on postharvest anthracnose susceptibility. This is the first record of such an effect for avocado. The severity and incidence of anthracnose was significantly lower on ‘Hass’ grafted to ‘Velvick’ Guatemalan seedling rootstock compared with the ‘Duke 6’ Mexican seedling rootstock. Differences in anthracnose susceptibility were related to significant differences in concentrations of antifungal dienes in the leaves and mineral nutrients in the leaves and fruits from trees grafted to different rootstocks. Leaf diene concentrations were up to 1.5 times higher in ‘Hass’ trees on the ‘Velvick’ than the ‘Duke 6’ rootstock. In ungrafted nursery stock trees, diene concentrations were around 3 times higher in ‘Velvick’ than ‘Duke 6’ leaves. The ‘Velvick’/‘Hass’ combination also had a significantly lower leaf N concentration, a significantly higher fruit flesh Mn concentration, and significantly lower and higher leaf N/Ca and Ca+Mg/K ratios, respectively. A significant correlation (r = 0.82) between anthracnose severity and skin N/Ca ratio was also evident

Temperature and strain rate dependence of microstructural evolution and dynamic mechanical behavior in nanocrystalline Ti

The mechanical behavior of commercial purity titanium with a nanocrystalline (NC) grain size was investigated using split Hopkinson pressure bar tests at high strain rates and over a range of temperatures. The study was accompanied by detailed microstructural investigations before and after compression testing. The results show that rotary dynamic recrystallization operates during compressive deformation at strain rates of ~3000 and ~4500 s?1 at temperatures from 298 to 573 K but cells form at 673 K. The dynamic mechanical behavior of NC Ti shows a strong dependence on temperature and strain rate such that the flow stress and the strain hardening rate both increase with increasing strain and decreasing temperature. A constitutive equation is derived to relate the flow stress to the temperature, strain rate and true strain and to predict the yield strength and the peak stress of NC Ti subjected to dynamic deformation at elevated temperatures

Fundamentals of interface phenomena in advanced bulk nanoscale materials

The review is devoted to a study of interface phenomena influencing advanced properties of nanoscale materials processed by means of severe plastic deformation, high-energy ball milling and their combinations. Interface phenomena include processes of interface defect structure relaxation from a highly nonequilibrium state to an equilibrium condition, grain boundary phase transformations and enhanced grain boundary and triple junction diffusivity. On the basis of an experimental investigation, a theoretical description of the key interfacial phenomena controlling the functional properties of advanced bulk nanoscale materials has been conducted. An interface defect structure investigation has been performed by TEM, high-resolution x-ray diffraction, atomic simulation and modeling. The problem of a transition from highly non-equilibrium state to an equilibrium one, which seems to be responsible for low thermostability of nanoscale materials, was studied. Also enhanced grain boundary diffusivity is addressed. Structure recovery and dislocation emission from grain boundaries in nanocrystalline materials have been investigated by analytical methods and modeling