Re-examination of crack opening model of interface fracture

The complex singularity associated with a crack at the interface between two dissimilar, isotropic and homogeneous materials leads to mathematical artefacts, such as stress oscillations and crack face interpenetrations in the vicinity of the crack tip. To avoid these unrealistic features, Sinclair (Sinclair GB. On the stress singularity at an interface crack. International Journal of Fracture 1980;16(2):111-9) assumed a finite crack opening angle (COA) such that the singularity lambda became real equal to 1/2. This paper extends the COA model by considering real singularities not necessarily equal to 1/2. When COA is 0 degrees: the interface crack singularity is complex with a real part equal to 1/2. On increasing COA, the imaginary part of the singularity decreases and becomes zero at a threshold value of COA; at this point, the singularity is a real, repeated value. A further increase in COA results in a pair of real singularities. Different crack opening configurations and material combinations are studied, and results presented for threshold COAs and associated values of singularity. Stress analyses for these three regimes: (a) complex, (b) real pair and (c) real repeated singularities, are reported. It is seen that additional complexities are present in the last case. Typical results for stress fields are also included for comparing with standard fields. (C) 1999 Elsevier Science Ltd. All rights reserved.

Continuous distribution kinetics for ultrasonic degradation of poly(methyl methacrylate)

Ultrasonic degradation of poly(methyl methacrylate) (PMMA) was carried out in several solvents and some mixtures of solvents. The time evolution of molecular weight distribution (MWD), determined by gel permeation chromatography, is analysed by continuous distribution kinetics. The rate coefficients for polymer degradation are determined for each solvent. The variation of rate coefficients is correlated with the vapour pressure of the solvent, kinematic viscosity of the solution and solvent-polymer interaction parameters. The vapour pressure and the kinematic viscosity of the solution are found to be more critical than other parameters (such as the Huggins and Flory-Huggins constants) in determining the degradation rates. (C) 2001 Society of Chemical Industry.

Oxygen content of liquid cobalt in equilibrium with CoO.(1+x)Al2O3 and -Al2O3

The oxygen concentration of liquid cobalt in equilibrium with cobalt aluminate and a-alumina has been measured by suction sampling and crucible quenching techniques at temperatures between 1770 and 1975 K. Experiments were made with cobalt of high and low initial oxygen contents, and with and without the addition of cobalt aluminate. The effect of temperature on the equilibrium oxygen content is represented by the equation, log (at.% 0) = -10,4001T(K) + 4.64 (±0.008). The composition of the spinel phase, CoO.(1+x)AI20 3, saturated with alumina, has been determined by electron probe microanalysis. The values of x are 0.22 at 1770 Kand 0.28 at 1975 K. The oxygen potential corresponding to the three-phase equilibrium between cobalt, aluminate and alumina, and the standard Gibbs' energy of formation of nonstoichiometric cobalt aluminate are evaluated by combining the results of this study with recently published data on the activity of oxygen in liquid cobalt. Implications of the present results to aluminium deoxidation of liquid cobalt are discussed.

Embodied energy assessment of building materials in India using process and input-output analysis

Growing demand for urban built spaces has resulted in unprecedented exponential rise in production and consumption of building materials in construction. Production of materials requires significant energy and contributes to pollution and green house gas (GHG) emissions. Efforts aimed at reducing energy consumption and pollution involved with the production of materials fundamentally requires their quantification. Embodied energy (EE) of building materials comprises the total energy expenditure involved in the material production including all upstream processes such as raw material extraction and transportation. The current paper deals with EE of a few common building materials consumed in bulk in Indian construction industry. These values have been assessed based on actual industrial survey data. Current studies on EE of building materials lack agreement primarily with regard to method of assessment and energy supply assumptions (whether expressed in terms of end use energy or primary energy). The current paper examines the suitability of two basic methods; process analysis and input-output method and identifies process analysis as appropriate for EE assessment in the Indian context. A comparison of EE values of building materials in terms of the two energy supply assumptions has also been carried out to investigate the associated discrepancy. The results revealed significant difference in EE of materials whose production involves significant electrical energy expenditure relative to thermal energy use. (C) 2014 Elsevier B.V. All rights reserved.

Investigation of critical state in melt processed YBa2Cu3O7-δ thick films

The magnetic moment of square planar melt processed YBa2Cu3O7-δ thick films is observed to scale with the cube of the sample width at 4.2 K, suggesting that current flow on the length scale of the film determines its magnetization at this temperature. A well-defined discontinuity in slope in the scaling data at a sample width corresponding to the average grain size (≈2 mm) implies the coexistence of distinct intra- and inter-grain critical current densities of 1.1 × 105Acm-2 and 0.4 × 105Acm-2 at 1 T and 4.2 K. The presence of a critical state in the films at 4.2T is confirmed by removing the central section from a specimen. The observed change in magnetic moment is in excellent agreement with theory for fields greater than ≈2 T. A critical state is not observed at 77 K which suggests that the grains are only weakly coupled at the higher temperature. © 1994.

On the magnetospheric structure of pulsars

The magnetospheric structure of a pulsar is discussed for a non-force-free magnetic field. The local solution to the axisymmetric equations of the pulsar is obtained by the method of expanding in the polar angle. Particular attention is given to the solutions near the polar axis and the equator. Near the pulsar surface, the magnetic field energy density is found to be larger than the other energy components; the gravitational potential and the kinetic energy are relatively larger far away from the pulsar surface. It is shown that these relations influence the mass distribution in the pulsar magnetosphere. The results also show that the plasma rotation may be nonrigid and, hence, that a corotational region with a closed magnetic field may not exist.

Springs of Florida

bulletin which documented the major and important springs in the state (Ferguson et al., 1947). This publication was revised in 1977, with many previously undocumented springs and many new water-quality analyses being added (Rosenau et al., 1977). The Florida Geological Survey's report on first magnitude springs (Scott et al., 2002) was the initial step in once again updating and revising the Springs of Florida bulletin. The new bulletin includes the spring descriptions and water-quality analyses from Scott et al. (2002). Nearly 300 springs were described in 1977. As of 2004, more than 700 springs have been recognized in the state and more are reported each year. To date, 33 first magnitude springs (with a flow greater than 100 cubic feet per second or approximately 64.6 million gallons of water per day) have been recognized in Florida, more than any other state or country (Rosenau et al., 1977). Our springs are a unique and invaluable natural resource. A comprehensive understanding of the spring systems will provide the basis for their protection and wise use. (Document pdf contains 677 pages)

Orçamento Participativo : Emenda de Iniciativa Popular ao projeto de lei orçamentária da união para 2012

Este artigo tem como objetivo descrever e avaliar a experiência de orçamento participativo na União instrumentalizada por meio das emendas de iniciativa popular, incluídas no projeto de lei orçamentária para 2012, quando de sua apreciação pelo Congresso Nacional. Naquela oportunidade, depois de muitas discussões, foi aprovado o parecer preliminar que criou um mecanismo de participação direta do cidadão de pequenos municípios (até 50 mil habitantes) no orçamento da união. A experiência, apesar da ampla adesão e participação nas audiências públicas municipais, e de seu potencial como instrumento de aperfeiçoamento dos canais de participação social, sofreu, nos anos seguintes, dupla frustração. A primeira, porque nenhuma das programações orçamentárias incluídas pelas emendas de iniciativa popular foi empenhada, ou seja, nenhum dos 3.677 municípios contemplados no orçamento de 2012, a conta do orçamento participativo, recebeu quaisquer recursos. A segunda, pela ausência de continuidade dessa iniciativa no âmbito do Congresso Nacional, não retomada na apreciação dos projetos de leis orçamentárias de 2013 e 2014. A falta de apoio à iniciativa legislativa por parte do governo federal parece contraditória, considerando-se que o orçamento participativo era considerado como uma das marcas do partido dos trabalhadores, do ponto de vista ideológico-programático e doutrinário.

Ichthyoplankton of the continental shelf near Kodiak Island, Alaska

Eleven ichthyoplankton surveys were conducted (1 in 1972 and 10 between 1977 and 1979) in the northeastern Pacific Ocean over the continental shelf off Kodiak Island, Alaska. In the 677 neuston and 632 bongo tows, eggs or larvae of more than 80 fish taxa were found. They were present in every season and throughout the survey area, although more taxa and more individuals were found in summer than in other seasons. Among the more abundant species were the gadid Theragra chalcogramma and several hexagrammids and pleuronectids. The hexagrammids and several coUids were abundant in the neustonic layer, where they spent close to a year as larvae and prejuvenlles. Although the seasonal and geographic distribution of most taxa was complex, two patterns emerged: Late summer-fall spawners produce demersal eggs and have neustonic larvae that remain pelagic for several months (hexagrammids and some cottlds), and spring-summer spawners have pelagic eggs and larvae that spend several weeks in the plankton but are not closely associated with the surface (Theragra chalcogramma, pleuronectlds). (PDF file contains 95 pages.)

GIS application to boost fish production in Nigeria

The paper discusses the application of Geographic Information System (GIS) to fisheries management. The paper presents the importance of the emerging technology of GIS and how it can be utilized to greatly speed up and make more efficient location optimizing processes and how the technology can allow for a through examination of the many spatially variable factors which might affect or control fish production both from aquaculture and inland fisheries in Nigeria