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11

Electronic Resource

Straight Hemming of Aluminum Sheet Panels Using the Electromagnetic Forming Technology: First Approach (2007)

Jimbert, P. ; Perez, I. ; Eguia, I. ; [et al.]

s.l. ; Stafa-Zurich, Switzerland

Key engineering materials Vol. 344 (July 2007), p. 365-372

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ISSN: 1013-9826

Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008

Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Notes: Hemming is the last or one of the latest stage operations for the stamped parts. For thisreason it has a critical importance on the performance and perceived quality of assembled vehicles.It is used to attach two sheet metal parts together or to improve appearance creating a smooth edgerather than a razor edge with burrs.However, designing the hemmed union is not always easy and is deeply influenced by themechanical properties of the material of the bended part. Main problems for the automotive industryarise when bending aluminum alloys.Aluminum sheet is more difficult to hem due to its susceptibility to strain localization during thehemming process. This phenomenon produces cracking on the hemmed edge [1].In order to avoid this problem and due to the limitations of conventional flanging and hemmingtechnologies, the flange radii must be increased and a rope hem used (instead of the flat hem usedwith steels) when working with aluminum alloys. These changes on the design of the hem uniongive as a result a lower quality final product [2].Dies and tools used for the hemming process are designed based on experience and on lengthy andcostly die tryouts.Continuing with the development of new applications for the Electromagnetic Forming (EMF)technology, LABEIN-Tecnalia and Professor Glenn Daehn’s group from The Ohio State Universitycarried out some first straight flat hemming experiments using the AA 6016 T4 aluminum alloy.The results obtained from these first trials are presented in this paper giving a first sight of thepossibilities, advantages and disadvantages of using the Electromagnetic Forming technology forthe hemming of aluminum sheet panels.Using a non-clouped FEM simulation method, the experimental results are compared to the onesobtained with the simulations.The future working line in developing this new application for the Electromagnetic Formingtechnology will be based on the results obtained by this study

Type of Medium: Electronic Resource

URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/54/transtech_doi~10.4028%252Fwww.scientific.net%252FKEM.344.365.pdf

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12

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d-Hole localization and the suppression of superconductivity in YBa2(Cu1-xZnx)3O7−y (1988)

Jee, Chan -Soo ; Nichols, D. ; Kebede, A. ; [et al.]

Springer

Journal of superconductivity 1 (1988), S. 63-80

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ISSN: 1572-9605

Keywords: YBa2(Cu1−x Zn x )3O7−y ; electrical resistivity ; specific heat ; magnetic susceptibility ; electron paramagnetic resonance (EPR)

Source: Springer Online Journal Archives 1860-2000

Topics: Electrical Engineering, Measurement and Control Technology , Physics

Notes: Abstract The temperature and Zn concentration dependence of the electrical resistivity, specific heat, magnetic susceptibility, and electron paramagnetic resonance (EPR) spectra of YBa2(Cu1−x Zn x )3O7−y withy∼0.1 has been measured forx≤0.16. In addition, the temperature and field dependence of the magnetization has been measured for 2〈T〈300K and 0〈H〈9.0T, along with the temperature and quasihydrostatic pressure dependence of the electrical resistivity for selected samples for 0〈P〈13 GPa. The substitution of Zn for Cu in YBa2Cu3O7−y causes a rapid and nearly linear depression of the superconducting transition temperature,T c , withT c going to 0 K forx≥ 0.10. YBa2(Cu1−x Zn x )3O7−y retains the YBa2Cu3O7-y orthorhombic structure forx≤0.16 for both the superconducting and nonsuperconducting samples. Initially, the unit cell volume increases nearly linearly with Zn content; however, an abrupt change occurs in the vicinityx=0.8–0.10. Forx〈0.10, the temperature dependence of the electrical resistivity,ρ(T), is metallic-like (dρ/dT〉0) andρ increases gradually with increasing Zn content. However, forx≥ 0.10,ρ(T) becomes semiconductor-like, with a very rapid increase of the resistivity with increasingx. The electrical resistivity, magnetic susceptibility, EPR spectra, and specific heat all indicate that thed-holes associated with the Cu ions become localized in the nonsuperconducting phase,x〉-0.10.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00617952

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13

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Use of butanol-water mixtures for making wheat straw pulp (1999)

Jiménez, L. ; Maestre, F. ; Pérez, I.

Springer

Wood science and technology 33 (1999), S. 97-109

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ISSN: 0043-7719

Source: Springer Online Journal Archives 1860-2000

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Notes: Summary A central composite design was used to investigate the influence of the cooking conditions (time, temperature and butanol concentration) for wheat straw with butanol-water mixtures on the properties of the pulp obtained (yield and holocellulose, α-cellulose, lignin and ethanol-benzene extractives contents) and the pH of the resulting waste water. A second-order polynomial model consisting of three independent process variables was found to accurately describe the organosolv pulping of wheat straw. The equations derived predict the yield, the holocellulose, α-cellulose, lignin and ethanol-benzene extractives contents of the pulp, and the pH of the waste water with multiple-R, R2, adjusted-R2 and Snedecor' F values of 0.99, 0.99, 0.99 and 310.33; 0.98, 0.97, 0.95 and 56.63; 0.91, 0.84, 0.74 and 9.14; 0.99, 0.98, 0.96 and 70.52; 0.97, 0.94, 0.92 and 40.42; and 0.98, 0.95, 0.93 and 49.33, respectively. The process variables must be set at low values in order to ensure a high yield and pH. On the other hand, if a high holocellulose content and low lignin and ethanol-benzene extractives contents are to be obtained, then the process variables must be set at high values. Finally, obtaining pulp with a high α-cellulose content entails using a long cooking time and a high temperature, as well as a low butanol concentration.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s002260050102

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14

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Influence of process variables on the properties of pulp and paper sheets obtained by sulphite pulping of olive tree wood (2000)

Jiménez, L. ; Pérez, I. ; de la Torre, M. J. ; [et al.]

Springer

Wood science and technology 34 (2000), S. 135-149

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ISSN: 0043-7719

Source: Springer Online Journal Archives 1860-2000

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Notes: Summary A central composition design was developed to study the influence of process variables (temperature, pulping time, sulphite concentration, anthraquinone concentration and liquid/solid relation) on the properties of pulps (yield, holocellulose, α-cellulose and lignin contents, and brightness) and the paper sheets (stretch, burst index and tear index) obtained from them, in the sulphite pulping of olive tree wood. Equations that reproduce the properties of pulps prepared by sulphite pulping and of paper sheets obtained from it are reported. The proposed equations fit the experimental yield and the holocellulose and α-cellulose contents of the pulps with errors less than 5%, as well as brightness with errors less than 10%. Also, they reproduce the lignin content of the pulps, and the stretch, burst index and tear index of the paper sheets with errors less than 15%. Obtaining pulps with acceptably high yield, holocellulose and α-cellulose contents, and also a high brightness, in addition to low lignin contents, entails operating at a temperature of 193 °C for 143 min, using a sulphite concentration of 19.85%, an anthraquinone concentration of 0.1% and a liquid/solid relation of 6.24. These are also the most suitable conditions for obtaining paper sheets with a high stretch, burst index and tear index.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s002260000038

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15

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Several mechanisms in the elimination kinetics of ω-chlorocarboxylic acids in the gas phase (1995)

Chuchani, Gabriel ; Martin, Ignacio ; Rotinov, Alexandra ; [et al.]

Chichester : Wiley-Blackwell

Journal of Physical Organic Chemistry 8 (1995), S. 133-138

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ISSN: 0894-3230

Keywords: Organic Chemistry ; Physical Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology , Physics

Notes: The kinetics of the gas-phase pyrolysis of ω-chlorocarboxylic acids were examined in a seasoned static reaction vessel and in the presence of at least twice the amount of the free radical inhibitor cyclohexene or toluene. In conformity with the available experimental data on rate determination, these reactions proved to be unimolecular and obeyed a first-order rate law. The presence of the primary chlorine leaving group in Cl(CH2)nCOOH (n = 1-4) showed a change in mechanism from intramolecular displacement of the Cl leaving group by the acidic hydrogen of the COOH to anchimeric assistance of the carbonyl COOH to the C—Cl bond polarization in the transition state. This mechanistic consideration is nearly the same for the series of 2-, 3-, and 4-chlorobutyric acids. The chlorine atom at the 2-position of acetic, propionic and butyric acids is dehydrochlorinated through a prevailing reaction path involving a polar five-membered cyclic transition state.

Additional Material: 9 Tab.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/poc.610080302

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Estructura de las comunidades de la meiofauna de la Bahía de Nipe, Cuba (2008)

Cuervo, Z. ; Armenteros, M. ; Capetillo, N. ; [et al.]

CONyMA

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Publication Date: 2021-05-19

Description: The structure of meiofaunal communities was surveyed in 17 stations in Nipe Bay, Cuba in July, 2001. Levels of Nickel (all stations) are higher than in several bays in Cuba, probably due to natural causes. The levels of Copper, Zinc, Fe and Manganese indicate a relative low pollution, likely related to the presence of urban settlements. There is decrease in the total density and number of taxa of meiofauna in the stations with higher levels of metals; the copepods appear to be particularly sensitivity to metal pollution. The stations located at the mouth of the bay have the lowest levels of contamination and the highest total density of organisms and taxa richness, probably due to a more intense turnover of the waters in this area and consequent lower accumulation of pollutants in the sediments. The more inner stations exhibit higher levels of contamination and possess community structures characterized by low richness of taxa and reduced density of meiofauna.

Description: Published

Keywords: Heavy metals ; Meiobenthos ; Heavy metals ; Meiofauna ; Meiobenthos

Repository Name: AquaDocs

Type: Proceedings Paper , Non-Refereed

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Análisis comparativo del estado trófico de las aguas en la costa oriental de la provincia de Cienfuegos, Cuba. (2012)

Seisdedo, M. ; Moreira, A. ; Arencibia, G. ; [et al.]

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Publication Date: 2021-05-19

Description: El propósito de este trabajo es evaluar el estado trófico de las aguas en la costa oriental de la provincia de Cienfuegos, a partir de las concentraciones de nutrientes y del fitoplancton. Se utilizaron dos métodos de evaluación del estado trófico y se consideraron los resultados de nitrógeno inorgánico (NI), fósforo inorgánico (FI), Si y fitoplancton, los cuales se obtuvieron durante cuatro campañas de muestreo llevadas a cabo en el período 2006-2007. Se analizó la proporción elemental disponible Si/NI según criterio de Redfield, así como también se obtuvieron los coeficientes de correlaciones entre las concentraciones de nutrientes y fitoplancton. Los resultados mostraron al Si como el nutriente más disponible en el área de estudio y a las diatomeas como el grupo de fitoplancton predominante; sin embargo, sus concentraciones no se correlacionaron significativamente, lo cual pudiera deberse a una respuesta no inmediata de este indicador biológico al cambio de nutriente. Las evaluaciones del estado trófico mostraron correspondencia entre los niveles de fitoplancton y de nutrientes; así como poco impacto en la calidad de las aguas de esta zona costera, desde el punto de vista trófico.

Description: The purpose of this work is to assess the trophic status of waters in the east coast of the Cienfuegos province, from the nutrients and phytoplankton concentrations. Two methods of assessment of the trophic status were used and it were considered the results of inorganic nitrogen (IN), inorganic phosphorus (IP) and Si, which were obtained during four sampling campaigns carried out in the period 2006-2007. The available elementary proportion Si/IN was analyzed according to criterion of Redfield, as well as the correlation coefficients among the nutrients and phytoplankton concentrations were obtained. The results showed to the Si as the most available nutrient in the study area and to the diatoms like the phytoplankton group predominant; however, their concentrations were not correlated significantly and it could be due to a non immediate response of this biological indicator to the nutrient change. The assessments of the trophic status showed correspondence among the phytoplankton and nutrients levels; as well as little impact in the water quality of this coastal area, from the trophic point of view.

Description: Published

Description: ASW

Description: Cuba

Keywords: Trophic status ; Nutrients (mineral) ; Phytoplankton ; Coastal zone

Repository Name: AquaDocs

Type: Journal Contribution , Refereed , Article

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Regulatory changes in pterin and carotenoid genes underlie balanced color polymorphisms in the wall lizard (2019)

Andrade, Pedro ; Pinho, Catarina ; Pérez i de Lanuza, Guillem ; [et al.]

National Academy of Sciences

In: PNAS - Proceedings of the National Academy of Sciences of the United States of America. 2019; 116(12): 5633-5642. Published 2019 Feb 28. doi: 10.1073/pnas.1820320116.

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Publication Date: 2019-02-28

Description: Reptiles use pterin and carotenoid pigments to produce yellow, orange, and red colors. These conspicuous colors serve a diversity of signaling functions, but their molecular basis remains unresolved. Here, we show that the genomes of sympatric color morphs of the European common wall lizard (Podarcis muralis), which differ in orange and yellow pigmentation and in their ecology and behavior, are virtually undifferentiated. Genetic differences are restricted to two small regulatory regions near genes associated with pterin [sepiapterin reductase(SPR)] and carotenoid [beta-carotene oxygenase 2(BCO2)] metabolism, demonstrating that a core gene in the housekeeping pathway of pterin biosynthesis has been coopted for bright coloration in reptiles and indicating that these loci exert pleiotropic effects on other aspects of physiology. Pigmentation differences are explained by extremely divergent alleles, and haplotype analysis revealed abundant transspecific allele sharing with other lacertids exhibiting color polymorphisms. The evolution of these conspicuous color ornaments is the result of ancient genetic variation and cross-species hybridization.

Print ISSN: 0027-8424

Electronic ISSN: 1091-6490

Topics: Biology , Medicine , Natural Sciences in General