Electromagnetic induction and damping - quantitative experiments using PC interface

A bar magnet, attached to an oscillating system, passes through a coil periodically, generating a series of emf pulses. A novel method is described for the quantitative verification of Faraday's law which eliminates all errors associated with angular measurements, thereby revealing delicate features of the underlying mechanics. When electromagnetic damping is activated by short-circuiting the coil, a distinctly linear decay of oscillation amplitude is surprisingly observed. A quantitative analysis reveals an interesting interplay of the electromagnetic and mechanical time scales.Comment: 4 pages, to appear in Am. J. Phy

Response of nematode food webs to human induced disturbances

Modern human civilization occurs at the expense of biodiversity. Human activity has extensively transformed the land surface by agricultural intensification and urbanization. Notably, agricultural practices mainly tillage have diverse impacts on plants, soils and soil organisms. Tillage changes soil properties and affects organisms that are living in the soil. In addition, human activities such as burning of fossil fuels, urbanization, agriculture, deforestation and desertification are rapidly changing the world’s climate through the emission of greenhouse gases. Increase in the emission of greenhouse gases leads to global warming. Increase in air temperature congruently increases soil temperature, which could affect biodiversity in the soil. Nematodes are the most abundant multicellular soil organisms and are morphologically and functionally diverse. The objectives of this study were: 1) to assess the influence of agricultural intensification and urbanization on nematode communities by comparing different ecosystems through meta-analysis of published literature on a global scale, 2) to evaluate the effect of tillage on nematode communities in terms of increasing level of physical disturbance in an undisturbed forest ecosystem and 3) to investigate the response of nematodes to a 5 oC rise in soil temperature by simulating future global warming using heating cables in forest and agricultural ecosystems. Results from the meta-analyses indicated that overall richness was higher in forest than in natural grassland, disturbed grassland, urban, and agriculture ecosystems. In contrast, overall abundance was highest in disturbed grassland, agriculture and forest ecosystems. Effects of tillage on nematode communities suggested that it significantly reduced nematode richness but not abundance. Soil warming in agricultural site did not affect nematode abundance, whereas nematode richness was significantly decreased in the warming treatment. On the other hand, nematode abundance and richness were not affected by soil warming in the forest ecosystem. Results from the warming experiment support the idea that nematode communities in the forest ecosystem may be more resilient to environmental fluctuations than to communitites in agricultural ecosystems. Overall, this research strengthens the concept that human interventions adversely impact nematode richness, which is crucial for the maintenance of the full suite of ecosystem services provided by soil food webs

A heuristic procedure for one dimensional bin packing problem with additional constraints

We proposed a heuristic algorithm to solve the one-dimensional bin-packing problem with additional constraints. The proposed algorithm has been applied to solve a practical vehicle-allocation problem. The experimental results show that our proposed heuristic provides optimal or near-optimal results, and performs better than the first fit decreasing algorithm modified to incorporate additional constraints.

Multiple products, multiple constraints, single period inventory problem: A Hierarchical solution procedure

This paper presents the formulation and a hierarchical solution procedure of multiple products, multiple constraints, single period inventory problem. The hierarchical procedure decomposes the problem into a number of sub-problems equal to the number of constraints sets. Each sub-problem is solved optimally by applying Lagrange multipliers and satisfying Kuhn-Tucker conditions. The experimental results show that the hierarchical procedure performs well even when there are large a number of products and constraints.