Relationship between forest clearing and biophysical factors in tropical environments: Implications for the design of a forest change monitoring approach

The relationship between forest clearing, biophysical factors (e.g, ecological zones, slope gradient, soils), and transportation network in Costa Rica was analyzed. The location of forested areas at four reference datas (1940, 1950, 1961, and 1977) as derived from aerial photography and LANDSAT MSS data was digitilized and entered into a geographically-referenced data base. Ecological zones as protrayed by the Holdridge Life Zone Ecology System, and the location of roads and railways were also digitized from maps of the entire country as input to the data base. Information on slope gradient and soils was digitized from maps of a 21,000 square kilometer area. The total area of forest cleared over four decades are related to biophysical factors was analyzed within the data base and deforestation rates and trends were tabulated. The relatiohship between forest clearing and ecological zone and the influence of topography, sils, and transportation network are presented and discussed

A Note on Mirror Symmetry for Manifolds with Spin(7) Holonomy

Starting from the superconformal algebras associated with $G_2$ manifolds, I extend the algebra to the manifolds with spin(7) holonomy. I show how the mirror symmetry in manifolds with spin(7) holonomy arises as the automorphism in the extended sperconformal algebra. The automorphism is realized as 14 kinds of T-dualities on the supersymmetric $T^4$ toroidal fibrations. One class of Joyce's orbifolds are pairwise identified under the symmetry.Comment: 12 pages, harvmac bi

Integrating Dynamics and Wear Modelling to Predict Railway Wheel Profile Evolution

The aim of the work described was to predict wheel profile evolution by integrating multi-body dynamics simulations of a wheelset with a wear model. The wear modelling approach is based on a wear index commonly used in rail wear predictions. This assumes wear is proportional to Tγ, where T is tractive force and γ is slip at the wheel/rail interface. Twin disc testing of rail and wheel materials was carried out to generate wear coefficients for use in the model. The modelling code is interfaced with ADAMS/Rail, which produces multi-body dynamics simulations of a railway wheelset and contact conditions at the wheel/rail interface. Simplified theory of rolling contact is used to discretise the contact patches produced by ADAMS/Rail and calculate traction and slip within each. The wear model combines the simplified theory of rolling contact, ADAMS/Rail output and the wear coefficients to predict the wear and hence the change of wheel profile for given track layouts

Spanning tree generating functions and Mahler measures

We define the notion of a spanning tree generating function (STGF) $\sum a_n z^n$, which gives the spanning tree constant when evaluated at $z=1,$ and gives the lattice Green function (LGF) when differentiated. By making use of known results for logarithmic Mahler measures of certain Laurent polynomials, and proving new results, we express the STGFs as hypergeometric functions for all regular two and three dimensional lattices (and one higher-dimensional lattice). This gives closed form expressions for the spanning tree constants for all such lattices, which were previously largely unknown in all but one three-dimensional case. We show for all lattices that these can also be represented as Dirichlet $L$-series. Making the connection between spanning tree generating functions and lattice Green functions produces integral identities and hypergeometric connections, some of which appear to be new.Comment: 26 pages. Dedicated to F Y Wu on the occasion of his 80th birthday. This version has additional references, additional calculations, and minor correction

Transmission and group delay of microring coupled-resonator optical waveguides

We measured the transmission and group delay of microring coupled-resonator optical waveguides (CROWs). The CROWs consisted of 12 weakly coupled, microring resonators fabricated in optical polymers (PMMA on Cytop). The intrinsic quality factor of the resonators was 18,000 and the interresonator coupling was 1%, resulting in a delay of 110-140 ps and a slowing factor of 23-29 over a 17 GHz bandwidth

Polymer Microring Coupled-Resonator Optical Waveguides

We present measurements of the transmission and dispersion properties of coupled-resonator optical waveguides (CROWs) consisting of weakly coupled polymer microring resonators. The fabrication and the measurement methods of the CROWs are discussed as well. The experimental results agree well with the theoretical loss, waveguide dispersion, group delay, group velocity, and group-velocity dispersion (GVD). The intrinsic quality factors of the microrings were about 1.5 times 10^4 to 1.8 times 10^4, and group delays greater than 100 ps were measured with a GVD between -70 and 100 ps/(nm x resonator). With clear and simple spectral responses and without a need for the tuning of the resonators, the polymer microring CROWs demonstrate the practicability of using a large number of microresonators to control the propagation of optical waves

A new fabrication method for precision antenna reflectors for space flight and ground test

Communications satellites are using increasingly higher frequencies that require increasingly precise antenna reflectors for use in space. Traditional industry fabrication methods for space antenna reflectors employ successive modeling techniques using high- and low-temperature molds for reflector face sheets and then a final fit-up of the completed honeycomb sandwich panel antenna reflector to a master pattern. However, as new missions are planned at much higher frequencies, greater accuracies will be necessary than are achievable using these present methods. A new approach for the fabrication of ground-test solid-surface antenna reflectors is to build a rigid support structure with an easy-to-machine surface. This surface is subsequently machined to the desired reflector contour and coated with a radio-frequency-reflective surface. This method was used to fabricate a 2.7-m-diameter ground-test antenna reflector to an accuracy of better than 0.013 mm (0.0005 in.) rms. A similar reflector for use on spacecraft would be constructed in a similar manner but with space-qualified materials. The design, analysis, and fabrication of the 2.7-m-diameter precision antenna reflector for antenna ground tests and the extension of this technology to precision, space-based antenna reflectors are described

Integration of graduate employability skills through industry outsourced CDIO project

Engineering curricula in higher education should be aligned with the current and future requirements of the industry to ensure industry-ready graduates. In the UK GOV HE education and professional accredited bodies, it is required to embed graduate attributes into the engineering curriculum. Although the CDIO-based approach provides a platform where students can develop these skills, there is still a gap between students’ skills and industry compatibility due to a lack of interaction with industry. Our solution is to embed industry outsourced CDIO projects in modules across the engineering course curriculum. These modules provide students not only the opportunity to develop their engineering technical skills but also their employability skills for actual industrial environment. At our university, the academic team have adopted a robust 7-stage approach in consultation and collaboration with industry to identify and implement industry-sourced CDIO projects in the curriculum. Based on the nature and complexity of the project, the CDIO projects can be integrated into relevant modules at appropriate academic levels. For example, a design-related project can be integrated into the first-year module whereas complex projects are allocated to final-year students. The final objectives of the CDIO projects are aligned with the learning outcomes of the corresponding modules and should be reflected in the module assessments. In this paper, the approach and outcome of one of our industrial CDIO projects outsourced by eXroid (a biomedical company in the UK) have been described. During the period, students followed the four stages of CDIO framework. The performance of the students was satisfactory as 81% of the students passed the module on their first attempt and the average mark was 49.9. The feedback received from eXroid personnel and students regarding the project execution and outcome was outstanding. Students have also developed several industry-oriented technical and soft skills while executing the projects

Academic Support at Leeds Metropolitan Library

Leeds Metropolitan’s Library Academic Support Stream is made up of Academic Librarians and Information Services Librarians who provide academic support to the university’s six faculties. The team use innovative methods of working together to engage students and enhance their experience. The team only formed a year ago so this is a good time to reflect on our success so far. The library service at Leeds Met is continually developing and offers new challenges and opportunities for staff providing library academic support. Innovation has even become part of our new name – ‘Libraries and Learning Innovation’. We still offer all the traditions types of library academic support, but there is an increasing emphasis on finding innovative ways of supporting students and publicising what we can offer. This year the Library Academic Support Stream won a University Attitude Character and Talents Award for Future Focus