Rensselaer Polytechnic Institute

About: Rensselaer Polytechnic Institute is a education organization based out in Troy, New York, United States. It is known for research contribution in the topics: Terahertz radiation & Finite element method. The organization has 19024 authors who have published 39922 publications receiving 1414699 citations. The organization is also known as: RPI & Rensselaer Institute.

Venture Capitalists' Assessment of New Venture Survival

Abstract: This study investigates whether VCs' assessment policies of new venture survival are consistent with those arising from the strategy literature (using two established strategy perspectives) Strategy scholars suggest the nature of the markets, competition, and decisions made by the management team affect a new venture's survival chances The findings demonstrate that VCs' assessment policies are predominantly consistent with those proposed by strategy scholars-providing insight into why VCs consider certain criteria in their assessment of new venture survival as well as why some criteria are more important in their assessment than others Through this increased understanding of venture capitalists' decision making, entrepreneurs seeking capital may be better able to address their requests for funding to those criteria venture capitalists find most critical to the survival of a new venture Venture capitalists may use these findings to better understand their own decision making process, which, in turn, provides the opportunity to increase evaluation efficiency

Iron aluminides: present status and future prospects

Abstract: This paper constitutes a broad survey of the physical, mechanical and corrosion properties of Fe3Al alloys, as well as a review of principal processing methods. This class of alloys, once thought to be inherently brittle, is shown to possess moderate ductility, provided that mechanical testing is carried out in an inert environment. Methods to improve mechanical properties by alloying and microstructural control are described. The influence of alloying elements on corrosion and stress corrosion resistance and weldability also is reviewed.

Climate-driven declines in arthropod abundance restructure a rainforest food web.

Abstract: A number of studies indicate that tropical arthropods should be particularly vulnerable to climate warming. If these predictions are realized, climate warming may have a more profound impact on the functioning and diversity of tropical forests than currently anticipated. Although arthropods comprise over two-thirds of terrestrial species, information on their abundance and extinction rates in tropical habitats is severely limited. Here we analyze data on arthropod and insectivore abundances taken between 1976 and 2012 at two midelevation habitats in Puerto Rico’s Luquillo rainforest. During this time, mean maximum temperatures have risen by 2.0 °C. Using the same study area and methods employed by Lister in the 1970s, we discovered that the dry weight biomass of arthropods captured in sweep samples had declined 4 to 8 times, and 30 to 60 times in sticky traps. Analysis of long-term data on canopy arthropods and walking sticks taken as part of the Luquillo Long-Term Ecological Research program revealed sustained declines in abundance over two decades, as well as negative regressions of abundance on mean maximum temperatures. We also document parallel decreases in Luquillo’s insectivorous lizards, frogs, and birds. While El Nino/Southern Oscillation influences the abundance of forest arthropods, climate warming is the major driver of reductions in arthropod abundance, indirectly precipitating a bottom-up trophic cascade and consequent collapse of the forest food web.

Linear Programming Boosting via Column Generation

Abstract: We examine linear program (LP) approaches to boosting and demonstrate their efficient solution using LPBoost, a column generation based simplex method. We formulate the problem as if all possible weak hypotheses had already been generated. The labels produced by the weak hypotheses become the new feature space of the problem. The boosting task becomes to construct a learning function in the label space that minimizes misclassification error and maximizes the soft margin. We prove that for classification, minimizing the 1-norm soft margin error function directly optimizes a generalization error bound. The equivalent linear program can be efficiently solved using column generation techniques developed for large-scale optimization problems. The resulting LPBoost algorithm can be used to solve any LP boosting formulation by iteratively optimizing the dual misclassification costs in a restricted LP and dynamically generating weak hypotheses to make new LP columns. We provide algorithms for soft margin classification, confidence-rated, and regression boosting problems. Unlike gradient boosting algorithms, which may converge in the limit only, LPBoost converges in a finite number of iterations to a global solution satisfying mathematically well-defined optimality conditions. The optimal solutions of LPBoost are very sparse in contrast with gradient based methods. Computationally, LPBoost is competitive in quality and computational cost to AdaBoost.

A low-latitude halo stream around the Milky Way

Abstract: We present evidence for a ring of stars in the plane of the Milky Way, extending at least from l = 180° to 227° with turnoff magnitude g ~ 19.5; the ring could encircle the Galaxy. We infer that the low Galactic latitude structure is at a fairly constant distance of R = 18 ± 2 kpc from the Galactic center above the Galactic plane and has R = 20 ± 2 kpc in the region sampled below the Galactic plane. The evidence includes 500 Sloan Digital Sky Survey spectroscopic radial velocities of stars within 30° of the plane. The velocity dispersion of the stars associated with this structure is found to be 27 km s-1 at (l, b) = (198°, - 27°), 22 km s-1 at (l, b) = (225°, 28°), 30 km s-1 at (l, b) = (188°, 24°), and 30 km s-1 at (l, b) = (182°, 27°). The structure rotates in the same prograde direction as the Galactic disk stars but with a circular velocity of 110 ± 25 km s-1. The narrow measured velocity dispersion is inconsistent with power-law spheroid or thick-disk populations. We compare the velocity dispersion in this structure with the velocity dispersion of stars in the Sagittarius dwarf galaxy tidal stream, for which we measure a velocity dispersion of 20 km s-1 at (l, b) = (165°, - 55°). We estimate a preliminary metallicity from the Ca II (K) line and color of the turnoff stars of [Fe/H] = -1.6 with a dispersion of 0.3 dex and note that the turnoff color is consistent with that of the spheroid population. We interpret our measurements as evidence for a tidally disrupted satellite of 2 × 107 to 5 × 108 M☉ that rings the Galaxy.