3,653 research outputs found
Electrochemical incineration of cresols: A comparative study between PbO2 and boron-doped diamond anodes
No full textThe electrooxidation of aqueous solutions containing 5 mM of o-, m- and p-cresol at pH 4.0 has been investigated using a flow filter-press reactor with a boron-doped diamond (BDD) under galvanostatic electrolysis. All cresols are degraded at similar rate up to attaining overall mineralization. Comparable treatment of the m-cresol effluent on PbO2 leads to partial electrochemical incineration. However, this pollutant is more rapidly removed with PbO2 than with BDD. The decay kinetics of all cresols follows a pseudo-first-order reaction. Aromatic intermediates such as 2-methylhydroquinone and 2-methyl-p-benzoquinone and carboxylic acids such as maleic, fumaric, pyruvic, malonic, tartronic, glycolic, glyoxylic, acetic, oxalic and formic, have been identified and followed during the m-cresol treatment by chromatographic techniques. From these oxidation by-products, a plausible reaction sequence for m-cresol mineralization on both anodes is proposed. The energy consumption for the corresponding electrochemical process is also calculated
Synthesis of binary transition metal nitrides, carbides and borides from the elements in the laser-heated diamond anvil cell and their structure-property relations
No full textTransition metal nitrides, carbides and borides have a high potential for industrial applications as they not only have a high melting point but are generally harder and less compressible than the pure metals. Here we summarize recent advances in the synthesis of binary transition metal nitrides, carbides and borides focusing on the reaction of the elements at extreme conditions generated within the laser-heated diamond anvil cell. The current knowledge of their structures and high-pressure properties like high-(p; T) stability, compressibility and hardness is described as obtained from experiments
Wear modelling of diamond-like carbon coatings against steel in deionised water
No full textDiamond-Like Carbon (DLC) coatings are thin protective surface coatings used to reduce friction and minimise wear in a wide range of applications. The focus of this work is the use of DLC coatings within Rolls-Royce’s pressurised water reactors. A strong understanding of material behaviour in this environment is compulsory due to the stringent safety requirements of the nuclear industry. Wear testing of a range of commercial DLC coatings against steel in water, and the dependence of the tribology on normal load, sliding distance, and environmental species, was examined. Wear depth was observed to increase with normal load, and increase non-linearly with sliding distance. Uniquely, it was suggested that the tribology of a DLC coating in water was controlled by the velocity accommodation mode (VAM) of the transfer layer. When interfacial sliding was the dominant VAM, the carbonaceous transfer layer was present at all times, and a low specific wear rate was observed. When shear and recirculation of debris was the dominant VAM, the carbonaceous transfer layer initially present was replaced by iron oxide species, and a high specific wear rate was observed as a result of a three-body mechanism involving hematite.Two individual wear models were developed to predict the wear depth of a DLC coating sliding against steel in water. Each model represents a novel extension to the current literature regarding the modelling of wear. Firstly, an analytical differential equation was derived to predict the wear depth of a ball and a flat surface, in relation to any phenomenological law for wear volume. Secondly, a unique formulation of an incremental wear model for an arbitrary geometry was developed for a DLC coating which included the growth of a transfer layer. An efficient methodology was presented to allow fast integration of the equations whilst damping numerical instabilities. A comparison between the analytic and computational wear models showed a strong agreement in the model predictions, with a comparative error of less than 5%
Conflict Diamonds
No full text’Conflict diamonds’ refers to the fatal role that diamonds are believed to have played in several African conflicts. The article analyzes the impact of diamond abundance on economic growth in light of the broader, previously discovered empirical finding of a ’curse of natural resources’. By extending the theory of appropriative conflict, a predator-prey game is outlined in which a rebel chooses between peaceful production and predation on natural resources controlled by the ruler. It is shown that whereas an increase in natural resources will increase the ruler’s public utility investments, it might also lead to a crowding-out of labor from the formal sector to the appropriative struggle, which depresses growth. As predicted by the model, a cross-country regression analysis suggests that diamond abundance has a negative relationship with economic growth in countries with weak institutions.diamonds, appropriative conflict, curse of natural resources, growth, predation.
R.M. Simmons presentation, Rena Smart book review
No full textR.M. Simmons of the Gospel Music Workshop of America gives a presentation on the African influence in the African American religious experience. He explains how African slaves brought to America their concept of music (utilitarian concept of music). Simmons further discusses the fusion between the utilitarian concept and the Western concept of religion resulting in spirituals. He also describes hymn categories in early forms of formal African American worship experiences. Simmons takes questions from the audience among which is Dr. Riggins Earl Jr. Video concludes with a book review on Christian Theology and Ethics by Rena Smart.The Atlanta University Center Robert W. Woodruff Library acknowledges the generous support of the National Endowment for Humanities - Humanities Collections and Reference Resources Implementation Project Grant in supporting the processing and digitization of a number of its major archival collections as part of the project: Spreading the Word: Expanding Access to African American Religious Archival Collections at the Atlanta University Center Robert W. Woodruff Library.</em
Velocity-Gradient Probability Distribution Functions in a Lagrangian Model of Turbulence
No full textThe Recent Fluid Deformation Closure (RFDC) model of lagrangian turbulence is recast in path-integral language within the framework of the Martin-Siggia-Rose functional formalism. In order to derive analytical expressions for the velocity-gradient probability distribution functions (vgPDFs), we carry out noise renormalization in the low-frequency regime and find approximate extrema for the Martin-Siggia-Rose effective action. We verify, with the help of Monte Carlo simulations, that the vgPDFs so obtained yield a close description of the single-point statistical features implied by the original RFDC stochastic differential equations
Optical characterization of double-nanotextured black diamond films
No full textDouble-nanotextured black diamond films with different geometries were fabricated by double-step femtosecond laser treatments at different split ratios of accumulated laser fluence. A “2D-like” pseudo-periodic nanostructure was obtained for the first time when the split ratio was slightly unbalanced in favour of the first step of the treatment, as inferred by scanning electron microscopy. Raman analysis showed that a residual biaxial stress, composed by a superposition of a tensile and a compressive component, is always present after the laser writing process, and that the two components tend to balance each other in the 2D pseudo-periodic case. Spectrophotometric measurements in the 200–2000 nm wavelength range returned outstanding solar absorptance values for all the fabricated films (reaching the unprecedented value of 99.1% in the “2D-like” structure), launching double-nanotextured black diamond as a possible alternative to black silicon as absorbing layer for high-efficiency solar cells. © 2018 Elsevier Lt
On The Structure Of Argon Assisted Amorphous Carbon Films
No full textWe report a study of amorphous carbon films prepared by ion beam assisted deposition (IBAD). X-ray and ultraviolet photoelectron spectroscopy were used for probing the photoelectron core level and valence band of the films, respectively. Raman spectra, stress, and film density were also determined. The intrinsic compressive stress and plasmon energy increase sharply for argon assisting energies up to 100 eV, and vary slightly for energy in the 100 eV to 650 eV range. The highest stress (>10 GPa) and plasmon energy (29.5 eV), achieved at about 400 eV argon assisting energy, are of the same order as those reported for highly tetrahedral amorphous carbon films. However, structural investigations indicate that the material is composed of a highly compressed and dense sp2 network.93796800Robertson, J., (1991) Progr. Solid State Chem., 21, p. 199MacKenzie, D.R., Muller, D., Pailthope, B.A., (1991) Phys. Rev. Lett., 67, p. 773Lifshitz, Y., Kasi, S.R., Rabalais, J.W., Eckstein, W., (1990) Phys. Rev. B, 41, p. 10468Robertson, J., (1993) Diamond Relat. Mater., 2, p. 984Cuomo, J.J., Doyle, J.P., Brutley, J., Liu, J.C., (1991) J. Vac. Sci. Technol. A, 9, p. 2210Gissler, W., Hammer, P., Haupt, J., (1994) Diamond Relat. Mater., 3, p. 770Andre, B., Rossi, F., Van Veen, A., Mijnarends, P.E., Schut, H., Delplancke, M.P., (1994) Thin Solid Films, 241, p. 171Hammer, P., Victoria, N.M., Alvarez, F., (1998) J. Vac. Sci. Technol. A, 16, p. 2491De Lima Jr., M.M., Lacerda, R.G., Vilcarromero, J., Marques, F.C., (1999) J. Appl. Phys., 86, p. 4636Marques, F.C., Lacerda, R.G., Odo, G.Y., Lepienski, C.M., (1998) Thin Solid Films, 332, p. 113Fallon, P.J., Veerasamy, V.S., Davis, C.A., Robertson, J., Amaratunga, G.A.J., Milne, W.I., Koskinen, J., (1993) Phys. Rev. B, 48, p. 4777Lifshitz, Y., Lempert, G.D., Grossman, E., Avigal, I., Uzan-Saguy, C., Kalish, R., Kulik, J., Rabalais, J.W., (1995) Diamond Relat. Mater., 4, p. 318Tay, B.K., Shi, X., Tan, H.S., Yang, H.S., Sun, Z., (1998) Surf. Coat. Technol., 105, p. 155Schafer, J., Ristein, J., Graupner, R., Ley, L., Stephann, U., Frauenheim, Th., Veerasamy, V.S., Ehrhardt, H., (1996) Phys. Rev. B, 53, p. 7762Amaratunga, G.A.J., Chhowalla, M., Keily, C.J., Alexandru, I., Devenish, R.M., (1996) Nature (London), 383, p. 321Lacerda, R.G., Marques, F.C., (1998) Appl. Phys. Lett., 73 (5), p. 617Lynch, R.W., Drickamer, H.G., (1966) J. Chem. Phys, 44, p. 18
An investigation of the environmental impact of surface diamond mining along the arid west coast of South Africa
No full textBibliography: leaves 178-188.An outline of the main features of the West Coast environment establishes that it has potential value for recreation, tourism and nature conservation,in addition to that of diamond mining, and that it is sensitive to disturbance. The diamond mining process is analysed and mining actions that cause environmental impact are identified. A matrix approach is employed to relate particular mining actions to specific environmental elements. It is found that there is major impact on scenic and vegetation elements and that primary impact is magnified significantly through the process of wind erosion. It is argued that much environmental impact can be prevented if the objective of environmental protection was incorporated into the management of mine sites and that unavoidable impact can be mitigated by rehabilitation,which is a reasonable requirement
MERCOSUR Union, Porter's Diamond and the Competitiveness of the Uruguayan Broiler Industry
No full textThis study focuses on the analysis and assessment of competitiveness within the
Uruguayan broiler industry. Porter's (1990) 'national diamond' was selected as the
appropriate framework for analysis and was applied to the six major Uruguayan broiler
firms.
This research reveals that the unique characteristics of the Uruguayan broiler industry are
successfully accommodated within the selected framework to explain the success of the
broiler industry against other meat substitutes. Therefore, this study has confirmed Porter's
(1990) diamond system as an adequate conceptualization of success in the Uruguayan
broiler industry. These results are consistent with those found in the existing literature,
lending support to the view that Porter's (1990) model seems to be applicable to
developing countries such as Uruguay.
However, some modifications of the model are required to fully explain the progress of
this industry. This research project presents an adaptation of Porter's (1990) 'diamond' to
the singularities of the firms investigated in this study.
This study opted for an industry-level case study research strategy that is operationalized
through in-depth personal interviews with owner directors and managers in six of the seven
possible organizations within Uruguay. This is augmented by further data collection
(additional interviews) through sources in government and market relevant bodies in order
to generate information on the national context. The selected research method showed its
utility for the investigation of weaknesses and strengths within the Uruguayan broiler
industry. These findings were used to accomplish the second objective of this research
which was to elaborate policy recommendations out of the primary and secondary
collected data that would help Uruguayan broiler firms to compete with international
broiler firms in a regional economic block (MERCOSUR) without barriers
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