Robustness issues in a data-driven spoken language understanding system

Robustness is a key requirement in spoken language understanding (SLU) systems. Human speech is often ungrammatical and ill-formed, and there will frequently be a mismatch between training and test data. This paper discusses robustness and adaptation issues in a statistically-based SLU system which is entirely data-driven. To test robustness, the system has been tested on data from the Air Travel Information Service (ATIS) domain which has been artificially corrupted with varying levels of additive noise. Although the speech recognition performance degraded steadily, the system did not fail catastrophically. Indeed, the rate at which the end-to-end performance of the complete system degraded was significantly slower than that of the actual recognition component. In a second set of experiments, the ability to rapidly adapt the core understanding component of the system to a different application within the same broad domain has been tested. Using only a small amount of training data, experiments have shown that a semantic parser based on the Hidden Vector State (HVS) model originally trained on the ATIS corpus can be straightforwardly adapted to the somewhat different DARPA Communicator task using standard adaptation algorithms. The paper concludes by suggesting that the results presented provide initial support to the claim that an SLU system which is statistically-based and trained entirely from data is intrinsically robust and can be readily adapted to new applications

First-principles materials design of high-performing bulk photovoltaics with the LiNbO3_3 structure

The bulk photovoltaic effect is a long-known but poorly understood phenomenon. Recently, however, the multiferroic bismuth ferrite has been observed to produce strong photovoltaic response to visible light, suggesting that the effect has been underexploited as well. Here we present three polar oxides in the LiNbO$_3$ structure that we predict to have band gaps in the 1-2 eV range and very high bulk photovoltaic response: PbNiO$_3$, Mg$_{1/2}$Zn$_{1/2}$PbO$_3$, and LiBiO$_3$. All three have band gaps determined by cations with $d^{10}s^0$ electronic configurations, leading to conduction bands composed of cation $s$-orbitals and O $p$-orbitals. This both dramatically lowers the band gap and increases the bulk photovoltaic response by as much as an order of magnitude over previous materials, demonstrating the potential for high-performing bulk photovoltaics

Enforcing Constitutional Rights Through Computer Code

Lawmaking and enforcement has advanced since Hammurabi first wrote out his legal code thousands of years ago. Today, the American legal system relies on legislatively-enacted federal, state, county, and municipal legal codes, agency-created regulations, the judge-made common law, and various law enforcement entities. This can be a confusing and complex system of rules and their explanations with varying degrees of enforcement. Blockchain technology is an automatic and efficient alternative to written codes that must be humanly-enforced. There has been limited scholarly interest in the implications of a legal application of blockchain technology to a political system but there have been few articles written that combine the implementation of blockchain to the political system in conjunction with smart contacts. While still theoretical, this note highlights the various ways in which already-existing blockchain technology can be applied to government actions through an overarching Social Smart Contract or Smart Constitution allowing for greater transparency and automatic self-enforcement of the law

Theory of the Bulk Photovoltaic effect in oxides, and First-Principles Computational Design of Materials with Bulk Dirac Points

Non-centrosymmetric crystals -- especially polar materials -- are capable of producing electric current in response to uniform illumination. This is called the bulk photovoltaic effect (BPVE), which we show can be identified with ``shift current\u27\u27 theory. Shift currents exhibit unique physics, which are discussed and clarified. A discrete form of the expression required for numerical implementation is derived that allows for robust and efficient calculation from first-principles calculations. The response for BaTiO3 and BiFeO3 is calculated and found to agree well with experiment, and careful analysis of the computed response reveals how the magnitude depends on structural and chemical properties, providing criteria for the search for and design of materials with large response. Additionally, the unique properties of shift currents allow for pure spin photocurrents in antiferromagnets with appropriate symmetry. We predict that these spin currents can be observed in BiFeO3 and hematite (Fe2O3), and calculate the expected response. Topological insulators are a class of materials that are bulk insulators with metallic surface states that take the form of helical Dirac cones protected by time-reversal symmetry. Here we explore phenomena that occur near or at the transition between the trivial and topological insulating phase. In Bi2Se3, the relationship between the topological gap and material strain is investigated and used to explore the topological phase transition. At the critical strain, there exists a bulk 3D Dirac point that is analogous to the 2D Dirac points in graphene, and may be expected to exhibit similar properties. However, this 3D Dirac point is not robust and can be easily gapped by perturbations. We propose that a 3D Dirac point marking a topological phase transition may be protected by spatial symmetries, and outline the constraints under which symmetry groups may contain materials with such points. Based on first principles calculations, we propose BiO2 in the β-cristobalite structure as a metastable 3D Dirac semimetal