Non-linear analysis of two-layer timber beams considering interlayer slip and uplift

A new mathematical model and its finite element formulation for the non-linear analysis of mechanical behaviour of a two-layer timber planar beam is presented. A modified principle of virtual work is employed in formulating the finite element method. The basic unknowns are strains. The following assumptions are adopted in the mathematical model: materials are taken to be non-linear and can differ from layer to layer; interacting shear and normal contact tractions between layers are derived from the non-linear shear contact traction-slip and the non-linear normal contact traction-uplift characteristics of the connectors; the geometrically linear and materially non-linear Bernoulli's beam theory is assumed for each layer. The formulation is found to be accurate, reliable and computationally effective. The suitability of the theory is validated by the comparison of the numerical solution and the experimental results of full-scale laboratory tests on a simply supported beam. An excellent agreement between measured and calculated results is observed for all load levels. The further objective of the paper is the analysis of the effect of different normal contact traction-uplift constitutive relationships on the kinematic and static quantities in a statically determined and undetermined structure. While the shear contact traction-slip constitutive relationship dictates the deformability of the composite beam and has a substantial influence on most of the static and kinematic quantities of the composite beam, a variable normal contact traction-uplift constitutive relationship is in most cases negligible

Determination of Sulphur (IV) Oxide in Ilorin City, Nigeria, During Dry Season

Ambient concentrations of sulphur (IV) oxide (SO2) have been determined in the city of Ilorin, Nigeria between mid February and mid Novembers 2003. SO2 levels were found to vary significantly with the traffic density and human activities. There was a significant difference (P = 0.05) between the SO2 concentrations at two sites (high and low traffic volume areas); however, there was no significant difference (P= 0.05) between high traffic/medium population density and medium traffic/high population density areas. The regression analysis indicated a strong correlation (r= 0.94) between the concentration of SO2 pattern and the hourly average traffic volume in all the sites. Average level found for the city was 59.3 \ub1 1.9ppb, which falls within the limits of the United States Environmental Protection Agency guidelines for air quality standards. Atmospheric pollution being one of the most dominant problems associated with urbanization, urban areas are associated with high density of industries and transport networks, among other infrastructure, which generate a wide range of air pollutants .@JASE

Direct reaction measurements with a 132Sn radioactive ion beam

The (d,p) neutron transfer and (d,d) elastic scattering reactions were measured in inverse kinematics using a radioactive ion beam of 132Sn at 630 MeV. The elastic scattering data were taken in a region where Rutherford scattering dominated the reaction, and nuclear effects account for less than 8% of the cross section. The magnitude of the nuclear effects was found to be independent of the optical potential used, allowing the transfer data to be normalized in a reliable manner. The neutron-transfer reaction populated a previously unmeasured state at 1363 keV, which is most likely the single-particle 3p1/2 state expected above the N=82 shell closure. The data were analyzed using finite range adiabatic wave calculations and the results compared with the previous analysis using the distorted wave Born approximation. Angular distributions for the ground and first excited states are consistent with the previous tentative spin and parity assignments. Spectroscopic factors extracted from the differential cross sections are similar to those found for the one neutron states beyond the benchmark doubly-magic nucleus 208Pb.Comment: 22 pages, 7 figure

Total phenolic content, antioxidative and antidiabetic properties of coconut (Cocos Nucifera L.) testa and selected bean seed coats

Natural alternatives tor the treatment of diabetes mellitus have been the interest of many researchers. In this study, the brown testas of mature coconuts were compared to beans seed coats of four varieties in terms of antioxidative and anti-hyperglycaemic properties. The total phenolic and flavonoid contents, the antioxidant potentials and the a-amvlase and a-glucosidase inhibitorv activities of the crude extracts were studied in vitro. The results showed that extracts of coconut testa and red kidney bean seed coat displayed higher a-glucosidase inhibition (IC50=19.90±5.67 and 4.84±1.43 μg/mL) and α-amylase inhibition (IC50=120.5±15.4 and 532.8±68.0 μg/mL) than the other extracts. These two extracts showed higher antioxidant capacities owing to their high phenolic and flavonoid contents. These results suggest that red kidney bean seed coat and tender coconut testa would have higher potential as nutraceuticals and could serve as natural alternative sources of anti-diabetic remedy

The magic nature of 132Sn explored through the single-particle states of 133Sn

Atomic nuclei have a shell structure where nuclei with 'magic numbers' of neutrons and protons are analogous to the noble gases in atomic physics. Only ten nuclei with the standard magic numbers of both neutrons and protons have so far been observed. The nuclear shell model is founded on the precept that neutrons and protons can move as independent particles in orbitals with discrete quantum numbers, subject to a mean field generated by all the other nucleons. Knowledge of the properties of single-particle states outside nuclear shell closures in exotic nuclei is important for a fundamental understanding of nuclear structure and nucleosynthesis (for example the r-process, which is responsible for the production of about half of the heavy elements). However, as a result of their short lifetimes, there is a paucity of knowledge about the nature of single-particle states outside exotic doubly magic nuclei. Here we measure the single-particle character of the levels in 133Sn that lie outside the double shell closure present at the short-lived nucleus 132Sn. We use an inverse kinematics technique that involves the transfer of a single nucleon to the nucleus. The purity of the measured single-particle states clearly illustrates the magic nature of 132Sn.Comment: 19 pages, 5 figures and 4 table

Direct neutron capture cross section on Ge 80 and probing shape coexistence in neutron-rich nuclei

Results are presented from the first neutron-transfer measurement on Ge80 using an exotic beam from the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory. Newly measured spins and spectroscopic factors of low-lying states of Ge81 are determined, and the neutron capture cross section on Ge80 was calculated in a direct-semidirect model to provide a more realistic (n,γ) reaction rate for r-process simulations. Furthermore, a region of shape coexistence around N≈50 is confirmed and implications for the magic nature of Ni78 are discussed

First proton-transfer study of 18F+p resonances relevant for novae

The 18F(p,α)15O reaction is the predominant destruction mechanism in novae of the radionuclide F18, a target of γ-ray observatories. Thus, its rate is important for understanding F18 production in novae. We have studied resonances in the 18F+p system by making a measurement of a proton-transfer reaction 18F(d,n). We have observed 15 Ne19 levels, 5 of which are below the proton threshold, including a subthreshold state, which has significant l p=0 strength. Our data provide a direct determination of the spectroscopic strength of these states and new constraints on their spins and parities, thereby resolving a controversy, which involves the 8- and 38-keV resonances. The 18F(p,α)15O reaction rate is reevaluated, which takes the subthreshold resonance and other new information determined in this experiment into account. © 2011 American Physical Society

Single-nucleon transfer reactions on \u3csup\u3e18\u3c/sup\u3eF

Simultaneous measurement of the proton-transfer 18F(d,n) 19Ne and neutron-transfer 18F(d,p)19F reactions were performed with a 18F radioactive beam at the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory. The experiments clarify the nuclear structure of 19Ne near the proton threshold, which is relevant for understanding the rates of proton-induced reactions on 18F in novae. Analogs for several states in the mirror nucleus 19F have not yet been identified in 19Ne, indicating that the level structure of 19Ne in this region is incomplete. We observed 15 levels in 19Ne from the 18F(d,n) 19Ne measurement and 18 levels in 19F from the 18F(d,p)19F measurement. Angular distributions were extracted for all strongly populated states and compared to distorted-wave Born approximation calculations. The angular distributions for all the known states in the two nuclei determined in this work are consistent with their previously assigned spins and parities. The spectroscopic factors determined for these levels in the two nuclei are reported. © 2011 American Physical Society

Neutron single particle structure in Sn131 and direct neutron capture cross sections

Recent calculations suggest that the rate of neutron capture by Sn130 has a significant impact on late-time nucleosynthesis in the r process. Direct capture into low-lying bound states is expected to be significant in neutron capture near the N=82 closed shell, so r-process reaction rates may be strongly impacted by the properties of neutron single particle states in this region. In order to investigate these properties, the (d,p) reaction has been studied in inverse kinematics using a 630MeV beam of Sn130 (4.8MeV/u) and a (CD 2) n target. An array of Si strip detectors, including the Silicon Detector Array and an early implementation of the Oak Ridge Rutgers University Barrel Array, was used to detect reaction products. Results for the Sn130(d, p)Sn131 reaction are found to be very similar to those from the previously reported Sn132(d, p)Sn133 reaction. Direct-semidirect (n,γ) cross section calculations, based for the first time on experimental data, are presented. The uncertainties in these cross sections are thus reduced by orders of magnitude from previous estimates. © 2012 American Physical Society