552 research outputs found
Beam Search Strategies for Neural Machine Translation
The basic concept in Neural Machine Translation (NMT) is to train a large
Neural Network that maximizes the translation performance on a given parallel
corpus. NMT is then using a simple left-to-right beam-search decoder to
generate new translations that approximately maximize the trained conditional
probability. The current beam search strategy generates the target sentence
word by word from left-to- right while keeping a fixed amount of active
candidates at each time step. First, this simple search is less adaptive as it
also expands candidates whose scores are much worse than the current best.
Secondly, it does not expand hypotheses if they are not within the best scoring
candidates, even if their scores are close to the best one. The latter one can
be avoided by increasing the beam size until no performance improvement can be
observed. While you can reach better performance, this has the draw- back of a
slower decoding speed. In this paper, we concentrate on speeding up the decoder
by applying a more flexible beam search strategy whose candidate size may vary
at each time step depending on the candidate scores. We speed up the original
decoder by up to 43% for the two language pairs German-English and
Chinese-English without losing any translation quality.Comment: First Workshop on Neural Machine Translation, 201
Multi-reference perturbation theory with Cholesky decomposition for the density matrix renormalization group
We present a second-order N-electron valence state perturbation theory
(NEVPT2) based on a density matrix renormalization group (DMRG) reference wave
function that exploits a Cholesky decomposition of the two-electron repulsion
integrals (CD-DMRG-NEVPT2). With a parameter-free multireference perturbation
theory approach at hand, the latter allows us to efficiently describe static
and dynamic correlation in large molecular systems. We demonstrate the
applicability of CD-DMRG-NEVPT2 for spin-state energetics of spin-crossover
complexes involving calculations with more than 1000 atomic basis functions. We
first assess in a study of a heme model the accuracy of the strongly- and
partially-contracted variant of CD-DMRG-NEVPT2 before embarking on resolving a
controversy about the spin ground state of a cobalt tropocoronand complex.Comment: 9 pages, 4 figures, 2 table
Direct Democracy: Protest Catalyst or Protest Alternative?
This paper presents the first investigation of whether direct democracy supplements or undermines the attendance of demonstrations as a form of protest behavior. A first approach assumes that direct democracy is associated with fewer protests, as they function as a valve that integrates voters' opinions, preferences, and emotions into the political process. A competing hypothesis proposes a positive relationship between direct democracy and this unconventional form of political participation due to educative effects. Drawing on individual data from recent Swiss Electoral Studies, we apply multilevel analysis and estimate a hierarchical model of the effect of the presence as well as the use of direct democratic institutions on individual protest behavior. Our empirical findings suggest that the political opportunity of direct democracy is associated with a lower individual probability to attend demonstration
Graphene quantum dots probed by scanning tunneling spectroscopy and transport spectroscopy after local anodic oxidation
Graphene quantum dots are considered as promising alternatives to quantum
dots in III-V semiconductors, e.g., for the use as spin qubits due to their
consistency made of light atoms including spin-free nuclei which both imply
relatively long spin decoherene times. However, this potential has not been
realized in experiments so far, most likely, due to a missing control of the
edge configurations of the quantum dots. Thus, a more fundamental investigation
of Graphene quantum dots appears to be necessary including a full control of
the wave function properties most favorably during transport spectroscopy
measurements. Here, we review the recent success in mapping wave functions of
graphene quantum dots supported by metals, in particular Ir(111), and show how
the goal of probing such wave functions on insulating supports during transport
spectroscopy might be achieved.Comment: 14 pages, review articl
Fluorescence Correlation Spectroscopy as a Quantitative Tool Applied to Drug Delivery Model Systems
The delivery of drugs to cells is a very active area of research. Drugs are commonly believed to ameliorate illnesses. The targeted, controlled and/or enhanced uptake of the drug into cells is facilitated by loading the drug into carrier vehicles (nanoparticles, e.g.. micelles).The distribution of a drug over the nanoparticles used to deliver the drug to the targeted cells is of vital importance. It makes a difference, whether all nanoparticles carry the same amount of drug or whether a little amount of the nanoparticles carries a high proportion of the drug material and most nanoparticles carry no material. This depends on the method used to load the drugs into the carriers. Furthermore, the absolute amount of drug present in the nanoparticles and the absolute number of nanoparticles loaded with drug molecules is very important, because "dosis venum facit" [Paracelsus]. We present an approach to resolve these issues by optical means.If the drug is fluorescent or labeled with a fluorescent label, fluorescence correlation spectroscopy (FCS) can be used to determine quantitative size distributions with a (confocal) microscope. In order to determine absolute concentrations the spatial dimensions of the confocal observation volume have to be known. These can be obtained from numerical simulations using vectorial diffraction theory. The theoretical results have been compared with experimental results from FCS using the calibration dye Rhodamine 6G. In a straightforward procedure the results were corrected for adsorption effects and excellent agreement to the theory was foun
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