3,691 research outputs found
The Random Bit Complexity of Mobile Robots Scattering
We consider the problem of scattering robots in a two dimensional
continuous space. As this problem is impossible to solve in a deterministic
manner, all solutions must be probabilistic. We investigate the amount of
randomness (that is, the number of random bits used by the robots) that is
required to achieve scattering. We first prove that random bits are
necessary to scatter robots in any setting. Also, we give a sufficient
condition for a scattering algorithm to be random bit optimal. As it turns out
that previous solutions for scattering satisfy our condition, they are hence
proved random bit optimal for the scattering problem. Then, we investigate the
time complexity of scattering when strong multiplicity detection is not
available. We prove that such algorithms cannot converge in constant time in
the general case and in rounds for random bits optimal
scattering algorithms. However, we present a family of scattering algorithms
that converge as fast as needed without using multiplicity detection. Also, we
put forward a specific protocol of this family that is random bit optimal ( random bits are used) and time optimal ( rounds are used).
This improves the time complexity of previous results in the same setting by a
factor. Aside from characterizing the random bit complexity of mobile
robot scattering, our study also closes its time complexity gap with and
without strong multiplicity detection (that is, time complexity is only
achievable when strong multiplicity detection is available, and it is possible
to approach it as needed otherwise)
Too Late! Influence of Temporal Delay on the Neural Processing of One’s Own Incidental and Intentional Action-Induced Sounds
The influence of delayed auditory feedback on action evaluation and execution of real-life action-induced sounds apart from language and music is still poorly understood. Here, we examined how a temporal delay impacted the behavioral evaluation and neural representation of hurdling and tap-dancing actions in a functional magnetic resonance imaging (fMRI) experiment, postulating that effects of delay diverge between the two, as we create action-induced sounds intentionally in tap dancing, but incidentally in hurdling. Based on previous findings, we expected that conditions differ regarding the engagement of the supplementary motor area (SMA), posterior superior temporal gyrus (pSTG), and primary auditory cortex (A1). Participants were videotaped during a 9-week training of hurdling and tap dancing; in the fMRI scanner, they were presented with point-light videos of their own training videos, including the original or the slightly delayed sound, and had to evaluate how well they performed on each single trial. For the undelayed conditions, we replicated A1 attenuation and enhanced pSTG and SMA engagement for tap dancing (intentionally generated sounds) vs. hurdling (incidentally generated sounds). Delayed auditory feedback did not negatively influence behavioral rating scores in general. Blood-oxygen-level-dependent (BOLD) response transiently increased and then adapted to repeated presentation of point-light videos with delayed sound in pSTG. This region also showed a significantly stronger correlation with the SMA under delayed feedback. Notably, SMA activation increased more for delayed feedback in the tap-dancing condition, covarying with higher rating scores. Findings suggest that action evaluation is more strongly based on top–down predictions from SMA when sounds of intentional action are distorted
Tailoring the gradient ultrafine-grained structure in low-carbon steel during drawing with shear
Conventional drawing and drawing with shear were conducted on the rods of low-carbon steel. Deformation by simple drawing forms basically a homogenous structure and leads to a uniform change in microhardness along the billet volume. A comparative analysis of the models of these processes showed that shear drawing of steel at room temperature reduces energy characteristics in half, normal forces on the die – by 1,8, and enhances the strain intensity from 0,5 to 1,6. During drawing with shear, strain-induced cementite dissolution occurs and a gradient structure is formed, which increases the microhardness of the surface layer up to values close to 7 000 MPa
Analysis of shear deformation scheme efficiency in plastic structure formation processes
The paper is devoted to the analysis of such an important factor as deformation behavior in the simple shear conditions.It is shown that non-monotonous character of material plastic flow exerts significant influence on the intensity of initial structure refinement. Induced non-monotonous character that ensures formation of equiaxed structural states plays an important role in the process
Synthesis of hierarchically structured materials: microporous diatoms and nanoporous hydroxyaluminosilicate
Motional sidebands and direct measurement of the cooling rate in the resonance fluorescence of a single trapped ion
Resonance fluorescence of a single trapped ion is spectrally analyzed using a
heterodyne technique. Motional sidebands due to the oscillation of the ion in
the harmonic trap potential are observed in the fluorescence spectrum. From the
width of the sidebands the cooling rate is obtained and found to be in
agreement with the theoretical prediction.Comment: 4 pages, 4 figures. Final version after minor changes, 1 figure
replaced; to be published in PRL, July 10, 200
Automated Implementation of Windows-related Security-Configuration Guides
Hardening is the process of configuring IT systems to ensure the security of
the systems' components and data they process or store. The complexity of
contemporary IT infrastructures, however, renders manual security hardening and
maintenance a daunting task.
In many organizations, security-configuration guides expressed in the SCAP
(Security Content Automation Protocol) are used as a basis for hardening, but
these guides by themselves provide no means for automatically implementing the
required configurations.
In this paper, we propose an approach to automatically extract the relevant
information from publicly available security-configuration guides for Windows
operating systems using natural language processing. In a second step, the
extracted information is verified using the information of available settings
stored in the Windows Administrative Template files, in which the majority of
Windows configuration settings is defined.
We show that our implementation of this approach can extract and implement
83% of the rules without any manual effort and 96% with minimal manual effort.
Furthermore, we conduct a study with 12 state-of-the-art guides consisting of
2014 rules with automatic checks and show that our tooling can implement at
least 97% of them correctly. We have thus significantly reduced the effort of
securing systems based on existing security-configuration guides
Accuracy of a method based on atomic absorption spectrometry to determine inorganic arsenic in food : Outcome of the collaborative trial IMEP-41
Peer reviewedPublisher PD
Temperature and strain rate dependence of microstructural evolution and dynamic mechanical behavior in nanocrystalline Ti
The mechanical behavior of commercial purity titanium with a nanocrystalline (NC) grain size was investigated using split Hopkinson pressure bar tests at high strain rates and over a range of temperatures. The study was accompanied by detailed microstructural investigations before and after compression testing. The results show that rotary dynamic recrystallization operates during compressive deformation at strain rates of ~3000 and ~4500 s?1 at temperatures from 298 to 573 K but cells form at 673 K. The dynamic mechanical behavior of NC Ti shows a strong dependence on temperature and strain rate such that the flow stress and the strain hardening rate both increase with increasing strain and decreasing temperature. A constitutive equation is derived to relate the flow stress to the temperature, strain rate and true strain and to predict the yield strength and the peak stress of NC Ti subjected to dynamic deformation at elevated temperatures
Microstructure and mechanical properties of AISi 304l austenitic stainless steel processed by various schedules of rolling
The paper studies various rolling schedules implemented at 500°С (incl. direct, reverse, and cross rolling) and their effect on the structure formation and mechanical properties in AISI 304L stainless steel samples. Both TEM and SEM research techniques were applied. An ultrafine grain-subgrain microstructure was found to be formed inside elongated original grains. Rolling-processed microstructural elements were close in their size with the minimum value observed after a reverse rolling (240 nm
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