400 research outputs found
Biologically Plausible Neural Model for the Recognition of Biological Motion and Actions
The visual recognition of complex movements and actions is crucial for communication and survival in many species. Remarkable sensitivity and robustness of biological motion perception have been demonstrated in psychophysical experiments. In recent years, neurons and cortical areas involved in action recognition have been identified in neurophysiological and imaging studies. However, the detailed neural mechanisms that underlie the recognition of such complex movement patterns remain largely unknown. This paper reviews the experimental results and summarizes them in terms of a biologically plausible neural model. The model is based on the key assumption that action recognition is based on learned prototypical patterns and exploits information from the ventral and the dorsal pathway. The model makes specific predictions that motivate new experiments
Light shifts in atomic Bragg diffraction
Bragg diffraction of an atomic wave packet in a retroreflective geometry with
two counterpropagating optical lattices exhibits a light shift induced phase.
We show that the temporal shape of the light pulse determines the behavior of
this phase shift: In contrast to Raman diffraction, Bragg diffraction with
Gaussian pulses leads to a significant suppression of the intrinsic phase shift
due to a scaling with the third power of the inverse Doppler frequency.
However, for box-shaped laser pulses, the corresponding shift is twice as large
as for Raman diffraction. Our results are based on approximate, but analytical
expressions as well as a numerical integration of the corresponding
Schr\"odinger equation.Comment: 6 pages, 5 figure
Molekulargenetische Analyse der equinen CRISP Gene und ihrer Rolle in der Fruchtbarkeit des Hengstes
[no abstract
Efficient protocols
The increasing demand for more and more computing power causes steady advancements of High Performance Computing (HPC) systems. The more powerful these systems will be in the future the further the number of processing units increases. A particularly important point in this context is the latency of the communication among those units, which significantly increases by the distance between two communication partners. One approach to positively influence the latency behavior is optimizing the underlying protocol structures in the overall system. Nowadays, different protocols are used for different communication distances. The latency can be improved by changing the protocol structure with two approaches. On the one hand, the used protocols can be changed to optimize the latency. On the other hand, the protocol structure can be unified. Thus, time-consuming protocol translations can be eliminated. In order to achieve this, a completely new protocol is required which unifies all features of the different protocol levels without compromising an efficient implementation.
This work is dedicated to the design of the new Unified Layer Protocol (ULP) providing a unified communication scheme which allows communication among all processing units at different levels of an HPC system. Initially, the main features of general protocols are analyzed in detail. Further, properties used by modern protocols use are introduced and their function is explained. The two protocols that are deemed most relevant, Hyper-Transport (HT) and Peripheral Component Interconnect Express (PCIe), are analyzed in detail regarding to the previously specified aspects. The insight gained through this analysis is incorporated into the development of the ULP. During the development process, first the structure of the ULP is defined and various parameters are determined. Special attention is turned on the feasibility in hardware and the scalability for large systems. The following comparison with HT and PCIe shows that the newly developed ULP usually provides superior performance, even when the effective communication distance moves close to the processor.
Further work is dedicated to the hardware development which first gave the inspiration for the development of the ULP. The insights gained during the development of the ULP were integrated into the hardware.
The results show that the ULP fulfills the demands for a protocol used in the field of HPC. This is achieved for both, the processor-near communication, as well as for the communication among different nodes. With the ULP the need for time and energy-consuming protocol conversions is eliminated, while the feasibility in hardware is obtained
Atomic diffraction from single-photon transitions in gravity and Standard-Model extensions
Single-photon transitions are one of the key technologies for designing and
operating very-long-baseline atom interferometers tailored for terrestrial
gravitational-wave and dark-matter detection. Since such setups aim at the
detection of relativistic and beyond-Standard-Model physics, the analysis of
interferometric phases as well as of atomic diffraction must be performed to
this precision and including these effects. In contrast, most treatments
focused on idealized diffraction so far. Here, we study single-photon
transitions, both magnetically-induced and direct ones, in gravity and
Standard-Model extensions modeling dark matter as well as
Einstein-equivalence-principle violations. We take into account relativistic
effects like the coupling of internal to center-of-mass degrees of freedom,
induced by the mass defect, as well as the gravitational redshift of the
diffracting light pulse. To this end, we also include chirping of the light
pulse required by terrestrial setups, as well as its associated modified
momentum transfer for single-photon transitions.Comment: 11 pages, 3 figures, 2 tables; This preprint has been submitted to
AVS Quantum Scienc
Optimal baseline exploitation in vertical dark-matter detectors based on atom interferometry
Several terrestrial detectors for gravitational waves and dark matter based
on long-baseline atom interferometry are currently in the final planning stages
or already under construction. These upcoming vertical sensors are inherently
subject to gravity and thus feature gradiometer or multi-gradiometer
configurations using single-photon transitions for large momentum transfer.
While there has been significant progress on optimizing these experiments
against detrimental noise sources and for deployment at their projected sites,
finding optimal configurations that make the best use of the available
resources are still an open issue. Even more, the fundamental limit of the
device's sensitivity is still missing. Here we fill this gap and show that (a)
resonant-mode detectors based on multi-diamond fountain gradiometers achieve
the optimal, shot-noise limited, sensitivity if their height constitutes 20% of
the available baseline; (b) this limit is independent of the dark-matter
oscillation frequency; and (c) doubling the baseline decreases the ultimate
measurement uncertainty by approximately 65%.Comment: 8 pages, 2 figure
HyperTransport 3 Core: A Next Generation Host Interface with Extremely High Bandwidth
As the amount of computing power keeps increasing, host interface bandwidth to memory and input-output devices (I/O) becomes a more and more limiting factor. High speed serial host interface protocols like PCI-Express and HyperTransport (HT) have been introduced to satisfy the applications’ ever increasing demands for more bandwidth. Recent applications in the field of General Purpose Graphic Processing Units (GPGPUs) and Field Programmable Gate Array (FPGA) based coprocessors are an example. In this Paper we present a novel implementation of an FPGA based HyperTransport 3 (HT3) host interface. To the best of our knowledge it represents the very first implementation of this type. The design offers an extremely high unidirectional bandwidth of up to 2.3 GByte/s. It can be employed in arbitrary FPGA applications and then offers direct access to an AMD Opteron processor via the HT interface. To allow the development of an optimal design, we perform a complexity and requirements analysis. The result is our proposed solution which has been implemented in synthesizable Hardware Description Language (HDL) code. Microbenchmarks are presented to show the feasibility and high performance of the design
Multi-Domain Norm-referenced Encoding Enables Data Efficient Transfer Learning of Facial Expression Recognition
People can innately recognize human facial expressions in unnatural forms,
such as when depicted on the unusual faces drawn in cartoons or when applied to
an animal's features. However, current machine learning algorithms struggle
with out-of-domain transfer in facial expression recognition (FER). We propose
a biologically-inspired mechanism for such transfer learning, which is based on
norm-referenced encoding, where patterns are encoded in terms of difference
vectors relative to a domain-specific reference vector. By incorporating
domain-specific reference frames, we demonstrate high data efficiency in
transfer learning across multiple domains. Our proposed architecture provides
an explanation for how the human brain might innately recognize facial
expressions on varying head shapes (humans, monkeys, and cartoon avatars)
without extensive training. Norm-referenced encoding also allows the intensity
of the expression to be read out directly from neural unit activity, similar to
face-selective neurons in the brain. Our model achieves a classification
accuracy of 92.15\% on the FERG dataset with extreme data efficiency. We train
our proposed mechanism with only 12 images, including a single image of each
class (facial expression) and one image per domain (avatar). In comparison, the
authors of the FERG dataset achieved a classification accuracy of 89.02\% with
their FaceExpr model, which was trained on 43,000 images
Peter Fendi und das einfigurige Wiener Sittenbild
Peter Fendis Bedeutung innerhalb der österreichischen Malerei der Biedermeierzeit mit besonderem Augenmerk auf seine Leistungen bei der Entwichlung der Sonderform des einfigurigen Wiener Sittenbildes.Peter Fendi and his position in austrian painting of the biedermeier period and his achievements developing the single figure genre paintin
Universality-of-Clock-Rates Test using Atom Interferometry with Scaling
We propose a competitive quantum test of the universality of clock rates that
depends on the proper time of a freely-falling particle, scaling cubic with the
laboratory time. In contrast to current tests with fountain clocks, our
proposed atom-interferometric scheme can be made robust against initial
conditions and recoil effects, making optical frequencies accessible even for
long interferometer durations. We study the influence of parasitic effects and
discuss implementations with strontium isotopes that may even outperform
current tests with fountain clocks.Comment: 9 pages, 3 figures, 1 tabl
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