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Work Presents (work + present)
Selected AbstractsOn introducing approximate solution methods in theory of elasticityCOMPUTER APPLICATIONS IN ENGINEERING EDUCATION, Issue 2 2006Autar Kaw Abstract This work presents how approximate solution methods were introduced in a graduate level course of Theory of Elasticity. The three methods introduced are the finite difference method, the finite element method, and the boundary element method. All methods are exemplified by the problem of a thick-walled cylinder subject to internal pressure with an axisymmetric response. Choosing a single problem to introduce the three methods demonstrates accuracy and efficacy of each method. © 2006 Wiley Periodicals, Inc. Comput Appl Eng Educ 14: 120,134, 2006; Published online in Wiley InterScience (www.interscience.wiley.com); DOI 10.1002/cae.20070 [source] Validation of numerical codes for impact and explosion cratering: Impacts on strengthless and metal targetsMETEORITICS & PLANETARY SCIENCE, Issue 12 2008E. PIERAZZO When properly benchmarked and validated against observation, computer models offer a powerful tool for understanding the mechanics of impact crater formation. This work presents results from the first phase of a project to benchmark and validate shock codes. A variety of 2D and 3D codes were used in this study, from commercial products like AUTODYN, to codes developed within the scientific community like SOVA, SPH, ZEUS-MP, iSALE, and codes developed at U.S. National Laboratories like CTH, SAGE/RAGE, and ALE3D. Benchmark calculations of shock wave propagation in aluminum-on-aluminum impacts were performed to examine the agreement between codes for simple idealized problems. The benchmark simulations show that variability in code results is to be expected due to differences in the underlying solution algorithm of each code, artificial stability parameters, spatial and temporal resolution, and material models. Overall, the inter-code variability in peak shock pressure as a function of distance is around 10 to 20%. In general, if the impactor is resolved by at least 20 cells across its radius, the underestimation of peak shock pressure due to spatial resolution is less than 10%. In addition to the benchmark tests, three validation tests were performed to examine the ability of the codes to reproduce the time evolution of crater radius and depth observed in vertical laboratory impacts in water and two well-characterized aluminum alloys. Results from these calculations are in good agreement with experiments. There appears to be a general tendency of shock physics codes to underestimate the radius of the forming crater. Overall, the discrepancy between the model and experiment results is between 10 and 20%, similar to the inter-code variability. [source] Combination of electric and magnetic dipoles with single-element feeding for broadband applicationsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 1 2006Karlo Q. da Costa Abstract This work presents four types of broadband compound antennas. The antennas are a combination of an electric dipole and small square or circular loops. The feeding of the electric dipole only is realized. The input impedance, reflection coefficient, and gain of the antennas with different geometries are analyzed numerically using the method of moments (MoM). It is shown that for the level of the reflection coefficient |,| < ,10 dB, 80% to 90% bandwidth can theoretically be achieved for the proposed antennas. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 8,12, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21248 [source] Gold electrodes modified with poly(4-aminophenol): incorporation of nitrogenated bases and an oligonucleotidePOLYMER INTERNATIONAL, Issue 4 2008Lucas F Ferreira Abstract BACKGROUND: Investigations of chemical modification of electrode surfaces and immobilization of nitrogenated bases and oligonucleotides are considered essential for the construction of DNA electrochemical nanodevices. Modification of gold electrode surfaces with poly(4-aminophenol) was carried out in order to produce polymers capable of immobilizing purine bases and oligonucleotides. RESULTS: Gold electrodes coated with poly(4-aminophenol) showed improved analytical characteristics and considerably enhanced the electrochemical signals associated with the detection of adenine and guanine by factors of ca 3 and ca 6, respectively, when compared with non-coated gold surfaces. Impedance studies indicated higher charge transfer impedance to modified electrodes containing adenosine monophosphate. Atomic force microscopy images showed that nitrogenated bases have a strong influence over the morphology of the modified electrode surface. It was observed that the modified electrode containing guanine presents globular morphology. CONCLUSION: The modified electrodes increased the amplitude of the current signal of nitrogenated bases when compared to non-coated gold surfaces and produced good response and peaks to the detection of an oligonucleotide. This work presents, for the first time, the electropolymerization of 4-aminophenol on gold electrodes, as well as the detection of nitrogenated bases and an oligonucleotide incorporated on these modified electrodes. Copyright © 2007 Society of Chemical Industry [source] Herding in online product choicePSYCHOLOGY & MARKETING, Issue 5 2006Jen-Hung Huang Previous research has shown that people are influenced by others when making decisions. This work presents three studies examining herding in product choices on the Internet. The first two studies addressed how two cues frequently found on the Internet, that is, sales volume and customer reviews, influence consumer on-line product choices. The third study examined the relative effectiveness of two recommendation sources. The experimental results revealed that subjects used the choices and evaluations of others as cues for making their own choices. However, herding effects are offset significantly by negative comments from others. Additionally, the recommendations of other consumers influence the choices of subjects more effectively than recommendations from an expert. Finally, implications of this work are discussed. © 2006 Wiley Periodicals, Inc. [source] Fragmentation pathways of some benzothiophene radical cations formed by atmospheric pressure chemical ionisationRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 5 2009Lisandra Cubero Herrera Polycyclic aromatic sulfur-containing compounds (PASHs) are commonly found in fossil fuels and are of considerable importance in environmental studies. This work presents detailed studies on the fragmentation patterns of radical cations formed from four representative PASHs, benzo[b]thiophene, dibenzothiophene, 4-methyldibenzothiophene and 4,6-dimethyldibenzothiophene, using tandem atmospheric pressure chemical ionization mass spectrometry (APCI-MS/MS). Understanding these fragmentation patterns can be a useful aid in the analysis of PASHs employing APCI or electron ionization (EI-MS/MS), either alone or in conjunction with liquid or gas chromatography. Copyright © 2009 John Wiley & Sons, Ltd. [source] Detection of 28 neurotransmitters and related compounds in biological fluids by liquid chromatography/tandem mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 9 2006Sophie Bourcier This work presents two liquid chromatography/tandem mass spectrometry (LC/MS/MS) acquisition modes: multiple reaction monitoring (MRM) and neutral loss scan (NL), for the analysis of 28 compounds in a mixture. This mixture includes 21 compounds related to the metabolism of three amino acids: tyrosine, tryptophan and glutamic acid, two pterins and five deuterated compounds used as internal standards. The identification of compounds is achieved using the retention times (RT) and the characteristic fragmentations of ionized compounds. The acquisition modes used for the detection of characteristic ions turned out to be complementary: the identification of expected compounds only is feasible by MRM while expected and unexpected compounds are detected by NL. In the first part of this work, the fragmentations characterizing each molecule of interest are described. These fragmentations are used in the second part for the detection by MRM and NL of selected compounds in mixture with and without biological fluids. Any preliminary extraction precedes the analysis of compounds in biological fluids. Copyright © 2006 John Wiley & Sons, Ltd. [source] Scion genotype controls biomass allocation and root development in grafted grapevineAUSTRALIAN JOURNAL OF GRAPE AND WINE RESEARCH, Issue 2 2010J.-P. TANDONNET Abstract Background and Aims:, Grafting is used in viticulture worldwide. Rootstocks are known to alter scion development or ,confer vigour' to varying degrees. This work examines scion/rootstock interactions in young grafted grapevines. Its aim was to determine the effects of scion and rootstock genotypes on biomass allocation within the plant. Methods and Results:, Five months after grafting, biomass allocation between the root and the shoot was measured for all the scion/rootstock combinations made between three Vitis genotypes. The scion genotype explained the highest percentage of the non-random variance for biomass allocation within the plant, including biomass allocation to the roots, i.e. it conferred differences in root vigour. In addition, we developed a double-grafted system, in which a single scion was grafted onto two rootstocks, to analyse further scion (or carbon source) effects on root development. Conclusions:, This work provides evidence of conferred root vigour by the scion which does not appear to be related to carbon supply from the shoot. The genotypes studied display varying levels of plasticity in their response to different grafting partners. Significance of the Study:, This work presents detailed analysis of biomass allocation within young grafted vines. In young grafted grapevines, the scion genotype has a major effect on most parameters of development, especially in the root. This aspect of rootstock/scion interactions should be taken into account when selecting rootstocks. A double-grafting system was developed for future research on signalling pathways and exchange mechanisms between scion and rootstock in grafted grapevine. [source] | |||||||||||||