Dark Radiation in LARGE Volume Models

We consider reheating driven by volume modulus decays in the LARGE Volume Scenario. Such reheating always generates non-zero dark radiation through the decays to the axion partner, while the only competitive visible sector decays are Higgs pairs via the Giudice-Masiero term. In the framework of sequestered models where the cosmological moduli problem is absent, the simplest model with a shift-symmetric Higgs sector generates 1.56 < N_{eff} - N_{eff,SM} < 1.74. For more general cases, the known experimental bounds on N_{eff} strongly constrain the parameters and matter content of the models.Comment: 6 pages; v2. refs update

Speeding up rendering of hybrid surface and volume models

Hybrid rendering of volume and polygonal model is an interesting feature of visualization systems, since it helps users to better understand the relationships between internal structures of the volume and fitted surfaces as well as external surfaces. Most of the existing bibliography focuses at the problem of correctly integrating in depth both types of information. The rendering method proposed in this paper is built on these previous results. It is aimed at solving a different problem: how to efficiently access to selected information of a hybrid model. We propose to construct a decision tree (the Rendering Decision Tree), which together with an auxiliary run-length representation of the model avoids visiting unselected surfaces and internal regions during a traversal of the model.Postprint (published version

Volume and Implicit Taper Functions For Cupressus Lusitanica and Pinus Patula Tree Plantations in Ethiopia

Data from Cupressus lusitanica and Pinus patula were used to develop total and exponential form merchantable volume models, and implicit taper functions. The exponential form merchantable volume model to a specified top diameter limit showed marked improvement compared with the unbounded non exponential form merchantable volume model of Burkhart (1977). Implicit taper functions derived from the exponential form merchantable volume models were found superior to taper functions obtained from the non exponential merchantable volume models. In general, these models are essential management tools for the plantation of the species and in particular provide stock volume estimates by end use type.Key words: C. lusitanica, Merchantable volume models, Taper functions, Total tree volume models, P. patula

Volume Modeling for Rapid Prototyping

The expanding workspace of Rapid Prototyping will draw on the new developments in geometric modeling. Volume modeling has substantial advantages over other modeling schemes to meet the emerging requirements of Rapid Prototyping technology. It provides us with a new approach to design complex geometry and topology. The integration of the volume modeling and Rapid Prototyping technology will help us to fully exploit RP's ability to fabricate objects with complex structures. This paper addresses our research and practice in a volume modeling system toward Rapid Prototyping. Novel techniques in volumetric data manipulation, NURBS volume models and triangular facet generation over solid models are presented. Computer models designed by this system and their corresponding DTM products are also shown atthe end of this paper.Mechanical Engineerin