586 research outputs found
Zur Berechnung von Klebverbindungen hybrider Karosseriestrukturen beim Lacktrocknungsprozess
Diese Arbeit liefert einen Beitrag zur Auslegung geklebter Karosserie-Mischbaustrukturen. Die derzeit verwendeten Strukturklebstoffe genĂŒgen komplexen mechanischen und schon im Fertigungsprozess hohen thermischen Beanspruchungen. Die Beschreibung der physikalischen, thermischen und mechanischen Eigenschaften des Klebstoffs ĂŒber den gesamten Prozess hinweg ist fĂŒr die Auslegung der Klebverbindung vor allem in Mischbaustrukturen entscheidend. Temperaturen von bis zu 200 °C im KTL-Lacktrocknungsprozess fĂŒhren zum einen zur Vernetzung der Klebstoffe, zum anderen aber auch zur thermischen Ausdehnung der artfremden Werkstoffpaarungen. Die so auftretenden Relativverschiebungen in groĂflĂ€chigen, geklebten Mischbaustrukturen können aufgrund der in dieser Arbeit vorgestellten Vorgehensweise schon in der Konzeptphase numerisch berechnet und die damit verbundenen bleibenden Deformationen sowie festigkeitsrelevanten Bereiche in der Klebschicht prognostiziert werden. FĂŒr die Dimensionierung der Klebverbindungen ist hiermit ein Nachweis der temperatur- und vernetzungsgradabhĂ€ngigen Klebstofffestigkeit unter mehrachsiger Beanspruchung erbracht worden
Topological aspects of numberings
We investigate connections between the syntactic and semantic
distance of programs on an abstract, recursion theoretic level.
For a certain rather restrictive notion of interdependency of
the two kinds of distances, there remain only few and
"unnatural" numberings allowing for such close relationship.
Weakening the requirements leads to the discovery of universal
metrics such that for an arbitrary recursively enumerable family
of functions a numbering compatible with such a metric can
uniformly be constructed. We conclude our considerations with
some implications on learning theory
Experimental Generation of SNP Haplotype Signatures in Patients with Sickle Cell Anaemia
Sickle cell anemia is caused by a single type of mutation, a homozygous AâT substitution in the Ă globin gene. Clinical severity is diverse, partially due to additional, disease-modifying genetic factors. We are studying one such modifier locus, HMIP (HBS1L-MYB intergenic polymorphism, chromosome 6q23.3). Working with a genetically admixed patient population, we have encountered the necessity to generate haplotype signatures of genetic markers to label genomic fragments with distinct genealogical origin at this locus. With the goal to generate haplotype signatures from patients experimentally, we have investigated the suitability of an existing nanofluidic assay platform to perform phase alignment with single-nucleotide polymorphism alleles.Patient DNA samples were loaded onto Fluidigm Digital Arrays and individual DNA molecules were assayed with allele-specific probes for SNP markers. Here we present data showing the utility of the nanofluidic approach, yielding haplotype data identical to those obtained with a family-based method. We then determined haplotype composition in a group of patients with sickle cell disease, including in those where a mathematical inference approach gave ambiguous or misleading results. Experimental phasing of genotypes across 3.8 kb for rs9399137, rs9402685, and rs11759553 created unequivocal haplotype signatures for each of the patients. In 68 patients, we found 8 copies of a haplotype signature ('C-C-T'), which is known to be prevalent in Europeans but to be absent in West African populations. We have confirmed the identity of our phased allele pairs by single-molecule sequencing and have demonstrated, in principle, that three-allele phasing (using three colors) is a potential extension to this method.Phased haplotypes yield more information than the individual marker genotypes. Procedures such as the one described here would therefore benefit genetic mapping and functional studies as well as diagnostic procedures where the identity or parental origin of short genetic fragments is of importance
Improved Arithmetic Performance by Combining Stateful and NonâStateful Logic in Resistive Random Access Memory 1Tâ1R Crossbars
Computing-in-memory (CIM) is a promising approach for overcoming the memory-wall problem in conventional von-Neumann architectures. This is done by performing certain computation tasks directly in the storage subsystem without transferring data between storage and processing units. Stateful and non-stateful CIM concepts are recently attracting lots of interest, which are demonstrated as logical complete, energy efficient, and compatible with dense crossbar structures. However, sneak-path currents in passive resistive random access memory (RRAM) crossbars degrade the operation reliability and require the usage of active 1 Transistorâ1 Resistance (1T-1R) bitcell designs. In this article, the arithmetic performance and reliability are investigated based on experimental measurements and variability-aware circuit simulations. Herein, it is aimed for the evaluation of logic operations specifically with fully integrated 1Tâ1R crossbar devices. Based on these operations, an N-bit full adder with optimized energy consumption and latency is demonstrated by combining stateful and non-stateful CIM logic styles with regard to the specific conditions in active 1Tâ1R RRAM crossbars
Picosecond Multilevel Resistive Switching in Tantalum Oxide Thin Films
The increasing demand for high-density data storage leads to an increasing
interest in novel memory concepts with high scalability and the opportunity of
storing multiple bits in one cell. A promising candidate is the redox-based
resistive switch repositing the information in form of different resistance
states. For reliable programming, the underlying physical parameters need to be
understood. We reveal that the programmable resistance states are linked to
internal series resistances and the fundamental nonlinear switching kinetics.
The switching kinetics of TaO-based cells was investigated in a
wide range over 15 orders of magnitude from 250 ps to 10 s. We found
strong evidence for a switching speed of 10 ps which is consistent with analog
electronic circuit simulations. On all time scales, multi-bit data storage
capabilities were demonstrated. The elucidated link between fundamental
material properties and multi-bit data storage paves the way for designing
resistive switches for memory and neuromorphic applications.Comment: Compiled PDF should contain 24 pages, 5 figures and 50 reference
Finite-Difference Time-Domain Simulation for Three-dimensional Polarized Light Imaging
Three-dimensional Polarized Light Imaging (3D-PLI) is a promising technique
to reconstruct the nerve fiber architecture of human post-mortem brains from
birefringence measurements of histological brain sections with micrometer
resolution. To better understand how the reconstructed fiber orientations are
related to the underlying fiber structure, numerical simulations are employed.
Here, we present two complementary simulation approaches that reproduce the
entire 3D-PLI analysis: First, we give a short review on a simulation approach
that uses the Jones matrix calculus to model the birefringent myelin sheaths.
Afterwards, we introduce a more sophisticated simulation tool: a 3D Maxwell
solver based on a Finite-Difference Time-Domain algorithm that simulates the
propagation of the electromagnetic light wave through the brain tissue. We
demonstrate that the Maxwell solver is a valuable tool to better understand the
interaction of polarized light with brain tissue and to enhance the accuracy of
the fiber orientations extracted by 3D-PLI.Comment: 13 pages, 5 figure
NeuroHammer: Inducing Bit-Flips in Memristive Crossbar Memories
Emerging non-volatile memory (NVM) technologies offer unique advantages in
energy efficiency, latency, and features such as computing-in-memory.
Consequently, emerging NVM technologies are considered an ideal substrate for
computation and storage in future-generation neuromorphic platforms. These
technologies need to be evaluated for fundamental reliability and security
issues. In this paper, we present \emph{NeuroHammer}, a security threat in
ReRAM crossbars caused by thermal crosstalk between memory cells. We
demonstrate that bit-flips can be deliberately induced in ReRAM devices in a
crossbar by systematically writing adjacent memory cells. A simulation flow is
developed to evaluate NeuroHammer and the impact of physical parameters on the
effectiveness of the attack. Finally, we discuss the security implications in
the context of possible attack scenarios
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