Title: Journal of Engineering Mathematics

Title: Journal of Engineering Mathematics

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ISSN: 0022-0833

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? Burger, R., Karlsen, K.H. and Towers, J.D. (2005), Closed-form and finite difference solutions to a population balance model of grinding mills. Journal of Engineering Mathematics, 51 (2), 165-195.

Full Text: J\J Eng Mat51, 165.pdf

Abstract: The wear of steel balls in continuously operated grinding mills, used in mineral processing to comminute metalliferous rocks, can be described by a simple population-balance model. This model gives rise to a scalar transport equation with a singular source term for the number density of balls as a function of size and time. Exact solutions to this equation are determined tinder the assumption of a simple power-law type wear law. It is shown that a particular term proposed in the engineering literature that describes the removal of used balls from the mill leads to negative solutions (Model 1). An alternative, more realistic term for the sieve action, which admits nonnegative solutions only, is introduced (Model 2). A working first-order finite-difference scheme for Model 2 and a second-order TVD variant are introduced and applied for numerical simulations along with an error study. A weak solution concept for Model 2 is proposed, uniqueness of weak solutions is shown, and convergence of the first-order scheme to a weak solution is established. These results hold for a general class of wear laws, not just power-law type.

Keywords: Finite-Difference Scheme, Linear Transport Equation, Numerical Simulation, Population Balance Model, TVD Scheme, Uniqueness and Existence, Dispersed Phase Systems, Ball Size Distributions, Mathematical-Model, Wear, Schemes, Breakage

Title: Journal of Engineering and Technology Management

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? Casper, S. and Murray, F. (2005), Careers and clusters: Analyzing the career network dynamic of biotechnology clusters. Journal of Engineering and Technology Management, 22 (1-2), 51-74.

Full Text: J\J Eng Tec Man22, 51.pdf

Abstract: Access to a pool of talented employees is an important element of entrepreneurial firms’ ability to build innovative capabilities. Through an empirical examination of two European biotechnology clusters – Cambridge, UK, and Munich, Germany – we investigate the degree to which macro-labor market institutions shape the micro-dynamics of career affiliation networks between scientific employees. Using bibliometric methods to trace careers and a series of social network analysis methods, we examine similarities and differences in career network dynamics across the two clusters. In particular, we investigate whether patterns of long-term employment within most German large firms, as opposed to more short-term employment in the United Kingdom, affects network structure, network performance and network composition in the two clusters. We show that contrary to the expectations of comparative institutional theory, network structures are grossly similar across the two clusters and, moreover, the performance of these networks as measured by “small-world” methods are similar; career affiliation networks in the two regions are formed through social interactions that appear largely unrelated to macro-institutional factors. Where the macro-institutional forces are effective is as a gatekeeper to network composition: the Cambridge network contains a roughly equal mix of scientists with recent industry and scientific experience, whereas the Munich network is populated almost entirely by academic scientists with no prior industrial experience.

Keywords: Affiliation, Application Networks, Bibliometric, Bibliometric Methods, Biotechnology Clusters, Careers, Comparative Institutional Forces, European Labor Markets, Industry, Innovation, Knowledge, Life, Network, Network Analysis, Performance, Small-World, Social Network Analysis, Start, Theory, United Kingdom

Title: Journal of Environmental Biology

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ISSN: 0254-8704

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? Saxena, A. (2006), Seasonal pattern of metal bioaccumulation and their toxicity on Sphagnum squarrosum. Journal of Environmental Biology, 27 (1), 71-75.

Abstract: Present study was undertaken as an attempt to study the effect of pollutants on biological responses of Sphagnum growing at Kainchi, Kumaon hills (Uttranchal). Sphagnum plants of almost identical size, collected from the marked sites of Kainchi in different seasons viz., monsoon, winter, summer and again in monsoon, were analysed for chlorophyll, protein, shoot length and nitrate reductase and peroxidase activities. Maximum chlorophyll, protein, shoots length and nitrate reductase activities were observed during the monsoon while minimum in summers. The abundance of Sphagnum and two other bryophytes, Marchantia and Plagiochasma was also higher in monsoon than in other seasons. The study also indicated that Sphagnum has more bioaccumulation and tolerance potential for heavy metals than Marchantia and Plagiochasma.

Keywords: Bryophytes, Metal Pollution, Phytotoxicity, Heavy-Metals, Moss Peat, Lead, Plants, Chlorophyll, Nitrate, Seedlings, Growth, Leaves, Zn