81 research outputs found
Anforderungen an eine eLearning-Plattform - Innovation und Integration
Die vorliegende Studie wurde vom Ministerium für Schule, Wissenschaft und Forschung (MSWF) in Auftrag gegeben und federführend vom LMR Dr. Ulrich Heinemann betreut. Das Ziel der Studie ist es, die Hochschulen bei der Festlegung der Anforderungen an eLearning-Plattformen zu unterstützen. Mit dieser Studie wollen wir den Hochschulen und dem MSWF ein Instrument an die Hand geben, gemeinsam mit Informatikern Fragen an die Konstrukteure von eLearning-Plattformen zu stellen und Antworten auszuwerten. Im Rahmen der Studie wurde unterscuht, welche Lehr-, Lern- und Verwaltungsprozesse dem Lehrbetrieb an Hochschulen zugrunde liegen. Aus diesem Prozessen werden funktionale und nicht-funktionale Anforderungen abgeleitet, die eine eLearning-Plattform erfüllen muss, um zur Unterstützung von Lehrenden und Lernenden an den Hochschulen eingesetzt werden zu können. Diese Anforderungen werden im einzelnen diskutiert, wobei insbesondere auch die Integration in existierende Hochschul-Infrastrukturen betrachtet wird. Die Ergebnisse dieser Studie können kurzfristig dazu benutzt werden, die Anforderungen an eine eLearning-Plattform zu konkretisieren. Auf dieser Basis können existierende Systeme evaluiert und ihr Anpassungsbedarf präzisiert werden. Längerfristig bietet die Studie die Grundlage für umfassende Analyse- und Beratungstätigkeiten eines Kompetenzzentrums zur Einführung von eLearning an Hochschulen, in dem dann neben der technischen und prozessorientierten Beratung u. a. auch eine Beratung im Bereich der Erstellung von multimedialen Lehreinheiten, im Bereich von didaktischen Konzepten bzw. im Bereich von Rechtefragen koodiniert und gebündelt werden könnte
The End of Logic Locking? A Critical View on the Security of Logic Locking
With continuously shrinking feature sizes of integrated circuits, the vast majority of semiconductor companies have become fabless, i.e., chip manufacturing has been outsourced to foundries across the globe.
However, by outsourcing critical stages of IC fabrication, the design house puts trust in entities which may have malicious intents. This exposes the design industry to a number of threats, including piracy via unauthorized overproduction and subsequent reselling on the black market.
One alleged solution for this problem is logic locking, also known as logic encryption, where the genuine functionality of a chip is “locked” using a key only known to the designer. If a correct key is provided, the design works as intended but with an incorrect key, the circuit produces faulty outputs. Unlocking is handled by the designer only after production, hence an adversarial foundry should not be able to unlock overproduced chips.
In this work, we highlight major shortcomings of proposed logic locking schemes.
They exist primarily due to the absence of a well-defined and realistic attacker model in the current literature. We characterize the physical capabilities of adversaries, especially with respect to invasive attacks and a malicious foundry.
This allows us to derive an attacker model that matches reality, yielding attacks against the foundations of locking schemes
beyond the usually employed SAT-based attacks. Our analysis, which is accompanied by two case studies, shows that none of the previously proposed logic locking schemes is able to achieve the intended protection goals against piracy in real-world scenarios.
As an important conclusion, we argue that there are strong indications that logic locking will most likely never be secure against a determined malicious foundry
Recycling and Assessment of Struvite Phosphorus from Sewage Sludge
AbstractThis study presents an integrated approach for the recovery of P from the wastewater path. Since natural P sources are limited, recycling processes are making an increasingly important contribution to meeting the nutritional requirements of plant production. The groundwork for developing a new fertilizer from upgraded sewage sludge includes an evaluation of nutrients and heavy metal contents. Struvite (NH4MgPO4 • 6 H2O) derived from sewage sludge had a total P content of 6.1% with 3.5% being water-soluble. Plant availability was tested in pot experiments with wheat and maize. P uptake rates were 66.7% and 85.9%, respectively. In terms of heavy metal contents, struvite showed contaminant levels at least three times below the limiting values of the German Sewage Sludge Ordinance. Stricter rules of the German Federal Soil Protection Act are also fulfilled if the loading of heavy metals is considered during periodical fertilization. This implies that P recovery as struvite may be one way of declaring a new type of fertilizer.
A model ensemble approach to determine the humus building efficiency of organic amendments in incubation experiments
Organic amendments are important to sustain soil organic matter (SOM) and soil functions in agricultural soils. Information about the contribution of organic amendments to SOM can be derived from incubation experiments. In this study, data from 72 incubated organic amendments including plant residues, digestates and manure were analysed. The incubation data was compiled from three experimental setups with varying incubation times, soils and incubation temperatures, in which CO2 release was measured continuously. The analysis of the incubation data was performed with an approach relying on conceptual parts of C-TOOL, CCB, Century, ICBM, RothC and Yasso which are all well-approved first-order carbon models that differ in structure and abstraction level. All models are an approximation of reality, whereby each model differs in understanding of the processes involved in soil carbon dynamics. To accumulate the advantages from each model a model ensemble was performed for each substrate. With the ability of each carbon model to compute the distribution of carbon into specific SOM pools a new approach for evaluating organic amendments in terms of humus building efficiency is presented that, depends on the weighted model fit of each ensemble member. Depending on the organic substrate added to the soil, the time course of CO2 release in the incubation studies was predicted with different accuracy by the individual model concepts. Averaging the output of the individual models leads to more robust prediction of SOM dynamics. The EHUM value is easy to interpret and the results are in accordance with the literature.Peer Reviewe
Biotic and abiotic properties mediating plant diversity effects on soil microbial communities in an experimental grassland
Faster elliptic-curve discrete logarithms on FPGAs
This paper accelerates FPGA computations of discrete logarithms
on elliptic curves over binary fields. As a toy example,
this paper successfully attacks the SECG standard curve sect113r2,
a binary elliptic curve that was not removed from the SECG standard until 2010 and was not disabled in OpenSSL until June 2015.
This is a new size record for completed ECDL computations,
using a prime order very slightly larger than the previous record holder. More importantly, this paper uses FPGAs much more efficiently,
saving a factor close to 3/2 in the size of each high-speed ECDL core. This paper squeezes 3 cores into a low-cost Spartan-6 FPGA
and many more cores into larger FPGAs. The paper also
benchmarks many smaller-size attacks to demonstrate reliability of the estimates, and covers a much larger curve over a 127-bit field to demonstrate scalability
Superfluid behaviour of a two-dimensional Bose gas
Two-dimensional (2D) systems play a special role in many-body physics.
Because of thermal fluctuations, they cannot undergo a conventional phase
transition associated to the breaking of a continuous symmetry. Nevertheless
they may exhibit a phase transition to a state with quasi-long range order via
the Berezinskii-Kosterlitz-Thouless (BKT) mechanism. A paradigm example is the
2D Bose fluid, such as a liquid helium film, which cannot Bose-condense at
non-zero temperature although it becomes superfluid above a critical phase
space density. Ultracold atomic gases constitute versatile systems in which the
2D quasi-long range coherence and the microscopic nature of the BKT transition
were recently explored. However, a direct observation of superfluidity in terms
of frictionless flow is still missing for these systems. Here we probe the
superfluidity of a 2D trapped Bose gas with a moving obstacle formed by a
micron-sized laser beam. We find a dramatic variation of the response of the
fluid, depending on its degree of degeneracy at the obstacle location. In
particular we do not observe any significant heating in the central, highly
degenerate region if the velocity of the obstacle is below a critical value.Comment: 5 pages, 3 figure
Non-Perturbative Renormalization Flow in Quantum Field Theory and Statistical Physics
We review the use of an exact renormalization group equation in quantum field
theory and statistical physics. It describes the dependence of the free energy
on an infrared cutoff for the quantum or thermal fluctuations. Non-perturbative
solutions follow from approximations to the general form of the coarse-grained
free energy or effective average action. They interpolate between the
microphysical laws and the complex macroscopic phenomena. Our approach yields a
simple unified description for O(N)-symmetric scalar models in two, three or
four dimensions, covering in particular the critical phenomena for the
second-order phase transitions, including the Kosterlitz-Thouless transition
and the critical behavior of polymer chains. We compute the aspects of the
critical equation of state which are universal for a large variety of physical
systems and establish a direct connection between microphysical and critical
quantities for a liquid-gas transition. Universal features of first-order phase
transitions are studied in the context of scalar matrix models. We show that
the quantitative treatment of coarse graining is essential for a detailed
estimate of the nucleation rate. We discuss quantum statistics in thermal
equilibrium or thermal quantum field theory with fermions and bosons and we
describe the high temperature symmetry restoration in quantum field theories
with spontaneous symmetry breaking. In particular, we explore chiral symmetry
breaking and the high temperature or high density chiral phase transition in
quantum chromodynamics using models with effective four-fermion interactions.Comment: 178 pages, appears in Physics Report
Data-driven analysis of interactions between people with dementia and a tablet device
Abstract
In the project I-CARE a technical system for tablet devices is developed that captures the personal needs and skills of people with dementia. The system provides activation content such as music videos, biographical photographs and quizzes on various topics of interest to people with dementia, their families and professional caregivers. To adapt the system, the activation content is adjusted to the daily condition of individual users. For this purpose, emotions are automatically detected through facial expressions, motion, and voice. The daily interactions of the users with the tablet devices are documented in log files which can be merged into an event list. In this paper, we propose an advanced format for event lists and a data analysis strategy. A transformation scheme is developed in order to obtain datasets with features and time series for popular methods of data mining. The proposed methods are applied to analysing the interactions of people with dementia with the I-CARE tablet device. We show how the new format of event lists and the innovative transformation scheme can be used to compress the stored data, to identify groups of users, and to model changes of user behaviour. As the I-CARE user studies are still ongoing, simulated benchmark log files are applied to illustrate the data mining strategy. We discuss possible solutions to challenges that appear in the context of I-CARE and that are relevant to a broad range of applications.</jats:p
Bottom-up effects of plant diversity on multitrophic interactions in a biodiversity experiment
Biodiversity is rapidly declining1, and this may negatively affect ecosystem processes, including economically important ecosystem services. Previous studies have shown that biodiversity has positive effects on organisms and processes4 across trophic levels. However, only a few studies have so far incorporated an explicit food-web perspective. In an eight-year biodiversity experiment, we studied an unprecedented range of above- and below-ground organisms and multitrophic interactions. A multitrophic data set originating from a single long-term experiment allows mechanistic insights that would not be gained from meta-analysis of different experiments. Here we show that plant diversity effects dampen with increasing trophic level and degree of omnivory. This was true both for abundance and species richness of organisms. Furthermore, we present comprehensive above-ground/below-ground biodiversity food webs. Both above ground and below ground, herbivores responded more strongly to changes in plant diversity than did carnivores or omnivores. Density and richness of carnivorous taxa was independent of vegetation structure. Below-ground responses to plant diversity were consistently weaker than above-ground responses. Responses to increasing plant diversity were generally positive, but were negative for biological invasion, pathogen infestation and hyperparasitism. Our results suggest that plant diversity has strong bottom-up effects on multitrophic interaction networks, with particularly strong effects on lower trophic levels. Effects on higher trophic levels are indirectly mediated through bottom-up trophic cascades
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