2,747 research outputs found
An efficient length- and rate-preserving concatenation of polar and repetition codes
We improve the method in \cite{Seidl:10} for increasing the finite-lengh
performance of polar codes by protecting specific, less reliable symbols with
simple outer repetition codes. Decoding of the scheme integrates easily in the
known successive decoding algorithms for polar codes. Overall rate and block
length remain unchanged, the decoding complexity is at most doubled. A
comparison to related methods for performance improvement of polar codes is
drawn.Comment: to be presented at International Zurich Seminar (IZS) 201
Conservation Provisions of the Food, Conservation and Energy Act of 2008: Evolutionary Changes and Challenges
Farm Bill, Conservation, Agricultural land retirement, Agricultural land preservation, Working lands, Agricultural and Food Policy, H59, Q58, Policy,
The Permafrost and Organic LayEr module for Forest Models (POLE-FM) 1.0
Climate change and increased fire are eroding the resilience of boreal forests. This is problematic because boreal vegetation and the cold soils underneath store approximately 30 % of all terrestrial carbon. Society urgently needs projections of where, when, and why boreal forests are likely to change. Permafrost (i.e., subsurface material that remains frozen for at least two consecutive years) and the thick soil-surface organic layers (SOLs) that insulate permafrost are important controls of boreal forest dynamics and carbon cycling. However, both are rarely included in process-based vegetation models used to simulate future ecosystem trajectories. To address this challenge, we developed a computationally efficient permafrost and SOL module that operates at fine spatial (1 ha) and temporal (daily) resolutions. The module mechanistically simulates daily changes in depth to permafrost, annual SOL accumulation, and their complex effects on boreal forest structure and functions. We coupled the module to an established forest landscape model, iLand, and benchmarked the model in interior Alaska at spatial scales of stands (1 ha) to landscapes (61,000 ha) and over temporal scales of days to centuries. The coupled model could generate intra- and inter-annual patterns of snow accumulation and active layer depth (portion of soil column that thaws throughout the year) consistent with independent observations in 17 instrumented forest stands. The model was also skilled at representing the distribution of near-surface permafrost presence in a topographically complex landscape. We simulated 34.6 % of forested area in the landscape as underlain by permafrost; a close match to the estimated 33.4 % from the benchmarking product. We further determined that the model could accurately simulate moss biomass, SOL accumulation, fire activity, tree-species composition, and stand structure at the landscape scale. Modular and flexible representations of key biophysical processes that underpin 21st-century ecological change are an essential next step in vegetation simulation to reduce uncertainty in future projections and to support innovative environmental decision making. We show that coupling a new permafrost and SOL module to an existing forest landscape model increases the model’s utility for projecting forest futures at high latitudes. Process-based models that represent relevant dynamics will catalyze opportunities to address previously intractable questions about boreal forest resilience, biogeochemical cycling, and feedbacks to regional and global climate. </p
English-learning infants’ perception of word stress patterns
Adult speakers of different free stress languages (e.g., English, Spanish) differ both in their sensitivity to lexical stress and in their processing of suprasegmental and vowel quality cues to stress. In a head-turn preference experiment with a familiarization phase, both 8-month-old and 12-month-old English-learning infants discriminated between initial stress and final stress among lists of Spanish-spoken disyllabic nonwords that were segmentally varied (e.g. [ˈnila, ˈtuli] vs [luˈta, puˈki]). This is evidence that English-learning infants are sensitive to lexical stress patterns, instantiated primarily by suprasegmental cues, during the second half of the first year of life
Streaming Tree Transducers
Theory of tree transducers provides a foundation for understanding
expressiveness and complexity of analysis problems for specification languages
for transforming hierarchically structured data such as XML documents. We
introduce streaming tree transducers as an analyzable, executable, and
expressive model for transforming unranked ordered trees in a single pass.
Given a linear encoding of the input tree, the transducer makes a single
left-to-right pass through the input, and computes the output in linear time
using a finite-state control, a visibly pushdown stack, and a finite number of
variables that store output chunks that can be combined using the operations of
string-concatenation and tree-insertion. We prove that the expressiveness of
the model coincides with transductions definable using monadic second-order
logic (MSO). Existing models of tree transducers either cannot implement all
MSO-definable transformations, or require regular look ahead that prohibits
single-pass implementation. We show a variety of analysis problems such as
type-checking and checking functional equivalence are solvable for our model.Comment: 40 page
AMADEUS: Towards the AutoMAteD secUrity teSting
The proper configuration of systems has become a fundamental
factor to avoid cybersecurity risks. Thereby, the analysis of cyber security vulnerabilities is a mandatory task, but the number of vul nerabilities and system configurations that can be threatened is ex tremely high. In this paper, we propose a method that uses software
product line techniques to analyse the vulnerable configuration of
the systems. We propose a solution, entitled AMADEUS, to enable
and support the automatic analysis and testing of cybersecurity
vulnerabilities of configuration systems based on feature models.
AMADEUS is a holistic solution that is able to automate the analy sis of the specific infrastructures in the organisations, the existing
vulnerabilities, and the possible configurations extracted from the
vulnerability repositories. By using this information, AMADEUS
generates automatically the feature models, that are used for rea soning capabilities to extract knowledge, such as to determine
attack vectors with certain features. AMADEUS has been validated
by demonstrating the capacities of feature models to support the
threat scenario, in which a wide variety of vulnerabilities extracted
from a real repository are involved. Furthermore, we open the door
to new applications where software product line engineering and
cybersecurity can be empowered.Ministerio de Ciencia, Innovación y Universidades RTI2018-094283-B-C33 (ECLIPSE)Junta de Andalucía P20-01224 (COPERNICA)Junta de Andalucía US-1381375 (METAMORFOSIS
Voltage-controlled electron-hole interaction in a single quantum dot
The ground state of neutral and negatively charged excitons confined to a
single self-assembled InGaAs quantum dot is probed in a direct absorption
experiment by high resolution laser spectroscopy. We show how the anisotropic
electron-hole exchange interaction depends on the exciton charge and
demonstrate how the interaction can be switched on and off with a small dc
voltage. Furthermore, we report polarization sensitive analysis of the
excitonic interband transition in a single quantum dot as a function of charge
with and without magnetic field.Comment: Conference Proceedings, Physics and Applications of Spin-Related
Phenomena in Semiconductors, Santa Barbara (CA), 2004. 4 pages, 4 figures;
content as publishe
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