Volume and homology of one-cusped hyperbolic 3-manifolds

Let M be a complete, finite-volume, orientable hyperbolic manifold having exactly one cusp. If we assume that pi_1(M) has no subgroup isomorphic to a genus-2 surface group, and that either (a) H_1(M;Z_p) has dimension at least 5 for some prime p, or (b) H_1(M;Z_2) has dimension at least 4, and the subspace of H^2(M;Z_2) spanned by the image of the cup product has dimension at most 1, then vol M > 5.06 If we assume that H_1(M;Z_2) has dimension at least 7, and that the compact core of M does not contain a genus-2 closed incompressible surface, then vol M > 5.06.Comment: 31 pages. This version agrees with the published version of the paper, except that an error in the published abstract has been corrected. In particular, the result which applies to manifolds with mod 2 homology of dimension at least 7 is stronger and has a shorter proof than the corresponding result in version

Learning to infer: RL-based search for DNN primitive selection on Heterogeneous Embedded Systems

Deep Learning is increasingly being adopted by industry for computer vision applications running on embedded devices. While Convolutional Neural Networks' accuracy has achieved a mature and remarkable state, inference latency and throughput are a major concern especially when targeting low-cost and low-power embedded platforms. CNNs' inference latency may become a bottleneck for Deep Learning adoption by industry, as it is a crucial specification for many real-time processes. Furthermore, deployment of CNNs across heterogeneous platforms presents major compatibility issues due to vendor-specific technology and acceleration libraries. In this work, we present QS-DNN, a fully automatic search based on Reinforcement Learning which, combined with an inference engine optimizer, efficiently explores through the design space and empirically finds the optimal combinations of libraries and primitives to speed up the inference of CNNs on heterogeneous embedded devices. We show that, an optimized combination can achieve 45x speedup in inference latency on CPU compared to a dependency-free baseline and 2x on average on GPGPU compared to the best vendor library. Further, we demonstrate that, the quality of results and time "to-solution" is much better than with Random Search and achieves up to 15x better results for a short-time search

Visitor Motivations for Technology Escape in Wisconsin\u27s Largest State Forest

Outdoor recreation managers are increasingly challenged with determining whether and how to provide opportunities for technology use in forests and parks. Decisions can be informed, in part, by better understanding visitor motivations regarding technology. To this end, four new “technology escape” motivation items were developed and measured in a survey of visitors to Northern Highland – American Legion State Forest. Visitors completed 815 surveys in summer 2013 (response rate = 90%). The four motivation items were grouped together into a single escape technology domain. Overall, NHAL visitors placed moderate importance on this motivation. Small differences in technology escape were found by respondent group size, gender, and place attachment. However, no significant relationships were found by primary activity, education level, age, income, or experience use history. Moderate to strong correlations suggest that the new technology specific domain may not be particularly distinct from existing recreation experience domains targeted at escaping everyday pressures

Rapid acceleration of electrons in the magnetosphere by fast-mode MHD waves

During major megnetic storms, enhanced flux of relativistic electrons in the inner magnetosphere have been observed to correleated with ULF waves. The enhancements can take place over a period of several hours. In order to account for such a rapid generation of relativistic electrons, we examine the mechanism of transit-time acceleration of electrons by low-frequency fast-mode MHD waves, here the assumed form of ULF waves. Calcaulations of the acceleration timescales in the model show that fast-mode waves in the Pc4 to Pc5 frequency range, with typically observed wave amplitudes 10--20 nT, can accelerate the seed electrons to energies of order MeV in a period of a few hours.Comment: 9 pages, 3 figures, Accepted to J. Geophys. Re

Incipient order in the t-J model at high temperatures

We analyze the high-temperature behavior of the susceptibilities towards a number of possible ordered states in the t-J-V model using the high-temperature series expansion. From all diagrams with up to ten edges, reliable results are obtained down to temperatures of order J, or (with some optimism) to J/2. In the unphysical regime, t<J, large superconducting susceptibilities are found, which moreover increase with decreasing temperatures, but for t>J, these susceptibilities are small and decreasing with decreasing temperature; this suggests that the t-J model does not support high-temperature superconductivity. We also find modest evidence of a tendency toward nematic and d-density wave orders. ERRATUM: Due to an error in the calculation, the series for d-wave supeconducting and extended s-wave superconducting orders were incorrect. We recalculate the series and give the replacement figures. In agreement with our earlier findings, we still find no evidence of any strong enhancement of the superconducting susceptibility with decreasing temperature. However, because different Pade approximants diverge from each other at somewhat higher temperatures than we originally found, it is less clear what this implies concerning the presence or absence of high-temperature superconductivity in the t-J model.Comment: 4 pages, 5 eps figures included; ERRATUM 2 pages, 3 eps figures correcting the error in the series for superconducting susceptibilitie

Explosive Event in MON-3 Oxidizer System Resulting from Pressure Transducer Failure

In 2003, a Druck(Registered Trademark) pressure transducer failed catastrophically in a test system circulating nitrogen tetroxide at NASA Johnson Space Center White Sands Test Facility. The cause of the explosion was not immediately obvious since the wetted areas of the pressure transducer were constructed of materials compatible with nitrogen tetroxide. Chemical analysis of the resulting residue and a materials analysis of the diaphragm and its weld zones were used to determine the chain of events that led to the catastrophic failure. Due to excessive dynamic pressure loading in the test system, the diaphragm in the pressure transducer suffered cyclic failure and allowed the silicon oil located behind the isolation diaphragm to mix with the nitrogen tetroxide. The reaction between these two chemicals formed a combination of 2,4-di and 2,4,6-trinitrophenol, which are shock sensitive explosives that caused the failure of the pressure transducer. Further research indicated numerous manufacturers offer similar pressure transducers with silicone oil separated from the test fluid by a thin stainless steel isolation diaphragm. Caution must be exercised when purchasing a pressure transducer for a particular system to avoid costly failures and test system contamination

Creation of a trajectory framework that is sustainable for a continuous exploration of Mars and its moons​

As humanity looks to the Cislunar region in recent space flight operations, the question remains: where will technology advance next? Mars is of particular interest with both the public and private sector aiming to get humans on the planet in the coming decades. Investigating stable trajectories in the Mars-Phobos-Deimos system for telecommunications and observation is the next step in developing future mission plans. Innovations in orbital mechanics must be considered, neither the Two Body Problem (2BP) nor the Circular Restricted Three Body Problem (CR3BP) are sufficient to effectively model satellite motion. Instead, in similar fashion to the patched-conics solution of transfers between the influence of celestial bodies, a patched CR3BP-2BP-CR3BP method of propagating the orbits is proposed. To begin, assumptions about Deimos and Phobos will be made—co-planar orbits and spherical symmetry to name a few. Once the problem has been successfully modeled, each assumption will be undone methodically to increase modeling accuracy. Impulsive maneuvers will be considered, as well as low, continuous thrust maneuvers. The aim of this project is to develop a robust, sustainable trajectory framework that can be used in future missions

Assessing Safety Culture within a Flight Training Organization

This study was prompted by a string of aircraft hull losses experienced by a multinational, multi-campus flight training organization. A mixed methods study was conducted to study the attitudes and perceptions of the operations and management staff at this flight training organization through the use of a survey instrument previously existing and adapted, in order to ensure validity, and interviews with key staff members. Confirmatory factor analysis was performed to identify underlying constructs in the perceptions and attitudes of the staff in order to identify beliefs that may signify a flight training organization is at risk. An analysis was conducted using these constructs, along with the interviews obtained from key individuals, to further understand the beliefs, attitudes, and perceptions that may place similar flight training organizations at risk. The research study identifies a lack of a safety culture throughout the organization. The current system is substantially reliant on the necessity of flight instructors and their students to maintain a clean record in order to be viable for future employment and is seen by this operator as the primary system for ensuring accountable action by agents within the system. The implementation of a Safety Management System is recommended as a result of this study