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Publikationen von Professorinnen und Professoren der HAW Hamburg

Alle : 1982, ... , 2017, 2018, 2019, 2020
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Alle : C. Schmidt, ... , Chica Lara, Chowdhury, Christ, ... , Czischke 
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Simon Ressel, Lucas Holtz, Niclas Janshen, Florian Bill, Antonio Chica, Thomas Flower, Claudia Weidlich und Thorsten Struckmann
State of charge monitoring of vanadium redox flow batteries using half cell potentials and electrolyte density
Journal of Power Sources, 378:776-783
28 Februar 2018

Marker: TI-MP

Andreas Reuter, Randy Bush, Italo Cunha, Ethan Katz-Bassett, Thomas C. Schmidt und Matthias Wählisch
Towards a Rigorous Methodology for Measuring Adoption of RPKI Route Validation and Filtering
Sigcomm Computer Communication Review, 48(1):19–27
Januar 2018

Marker: TI-I

Zusammenfassung: A proposal to improve routing security---Route Origin Authorization (ROA)---has been standardized. A ROA specifies which network is allowed to announce a set of Internet destinations. While some networks now specify ROAs, little is known about whether other networks check routes they receive against these ROAs, a process known as Route Origin Validation (ROV). Which networks blindly accept invalid routes? Which reject them outright? Which de-preference them if alternatives exist? Recent analysis attempts to use uncontrolled experiments to characterize ROV adoption by comparing valid routes and invalid routes. However, we argue that gaining a solid understanding of ROV adoption is impossible using currently available data sets and techniques. Our measurements suggest that, although some ISPs are not observed using invalid routes in uncontrolled experiments, they are actually using different routes for (non-security) traffic engineering purposes, without performing ROV. We conclude with a description of a controlled, verifiable methodology for measuring ROV and present three ASes that do implement ROV, confirmed by operators.

Ulfia A. Lenfers, Julius Weyl und Thomas Clemen
Firewood Collection in South Africa: Adaptive Behavior in Social-Ecological Models
Land, 7(3):97
ISSN: 2073-445X

Schlüsselwörter: Bushbuckridge,Canyon Biosphere,Kruger,MARS,adaptive behavior,ecological systems,firewood collection,goal,oriented action planning/GOAP,savanna,social,to

Zusammenfassung: \textlessp\textgreaterDue to the fact that the South Africa's savanna landscapes are under changing conditions, the previously sustainable firewood collection system in rural areas has become a social-ecological factor in questions about landscape management. While the resilience of savannas in national parks such as Kruger National Park (KNP) in South Africa has been widely acknowledged in ecosystem management, the resilience of woody vegetation outside protected areas has been underappreciated. Collecting wood is the dominant source of energy for rural households, and there is an urgent need for land management to find sustainable solutions for this complex social-ecological system. However, the firewood collection scenario is only one example, and stands for all “human-ecosystem service” interactions under the topic of over-utilization, e.g., fishery, grazing, harvesting. Agent-based modeling combined with goal-oriented action planning (GOAP) can provide fresh insights into the relationship between individual needs of humans and changes in land use. At the same time, this modeling approach includes adaptive behavior under changing conditions. A firewood collection scenario was selected for a proof-of-concept comprising households, collectors, ecosystem services and firewood sites. Our results have shown that, even when it is predictable what a single human agent will do, massive up-scaling is needed in order to understand the whole complexity of social-ecological systems. Under changing conditions, such as climate and an increasing population, fair distribution of natural goods become an important issue.\textless/p\textgreater


Raphael Hiesgen, Dominik Charousset und Thomas C. Schmidt
OpenCL Actors---Adding Data Parallelism to Actor-based Programming with CAF
Alessandro Ricci und Philipp Haller (Hrsg.) Programming with Actors - State-of-the-Art and Research Perspectives Band 10789 aus Lecture Notes on Computer Sciences (LNCS)
Seite 59--93.
Verlag: Springer Verlag, Berlin, Heidelberg, N.Y.
August 2018

Schlüsselwörter: Distributed Systems,

Marker: TI-I

Zusammenfassung: The actor model of computation has been designed for a seamless support of concurrency and distribution. However, it remains unspecific about data parallel program flows, while available processing power of modern many core hardware such as graphics processing units (GPUs) or coprocessors increases the relevance of data parallelism for general-purpose computation. In this work, we introduce OpenCL-enabled actors to the C++ Actor Framework (CAF). This offers a high level interface for accessing any OpenCL device without leaving the actor paradigm. The new type of actor is integrated into the runtime environment of CAF and gives rise to transparent message passing in distributed systems on heterogeneous hardware. Following the actor logic in CAF, OpenCL kernels can be composed while encapsulated in C++ actors, hence operate in a multi-stage fashion on data resident at the GPU. Developers are thus enabled to build complex data parallel programs from primitives without leaving the actor paradigm, nor sacrificing performance. Our evaluations on commodity GPUs, an Nvidia TESLA, and an Intel PHI reveal the expected linear scaling behavior when offloading larger workloads. For sub-second duties, the efficiency of offloading was found to largely differ between devices. Moreover, our findings indicate a negligible overhead over programming with the native OpenCL API.


Raphael Hiesgen, Dominik Charousset und Thomas C. Schmidt
A Configurable Transport Layer for CAF
Boston, MA
Proc. of the 9th ACM SIGPLAN Conf. on Systems, Programming, and Applications (SPLASH '18), Workshop AGERE! , Seite 1--12.
Verlag: ACM Digital Library, New York, NY, USA

Marker: TI-I

Zusammenfassung: The message-driven nature of actors lays a foundation for developing scalable and distributed software. While the actor itself has been thoroughly modeled, the message passing layer lacks a common definition. Properties and guarantees of message exchange often shift with implementations and contexts. This adds complexity to the development process, limits portability, and removes transparency from distributed actor systems. In this work, we examine actor communication, focusing on the implementation and runtime costs of reliable and ordered delivery. Both guarantees are often based on TCP for remote messaging, which mixes network transport with the semantics of messaging. However, the choice of transport may follow different constraints and is often governed by deployment. As a first step towards decoupling the messaging guarantees from the transport protocol, we present a redesigned network stack in the C++ Actor Framework (CAF) that allows to combine a transport protocol with additional functions for remote messaging. An evaluation quantifies the cost of composability and the impact of individual layers on the entire stack.

Quirin Scheitle, Oliver Gasser, Theodor Nolte, Johanna Amann, Lexi Brent, Georg Carle, Ralph Holz, Thomas C. Schmidt und Matthias Wählisch
The Rise of Certificate Transparency and Its Implications on the Internet Ecosystem
Internet Measurement Conference - IMC
Boston, MA
Proc. of ACM Internet Measurement Conference (IMC 2018) , Seite 343--349.
Association of the Computing Machinery
Verlag: ACM Digital Library, New York, NY, USA

Marker: TI-I

Zusammenfassung: In this paper, we analyze the evolution of Certificate Transparency (CT) over time and explore the implications of exposing certificate DNS names from the perspective of security and privacy. We find that certificates in CT logs have seen exponential growth. Website support for CT has also constantly increased, with now a majority of established connections supporting CT. With the increasing deployment of CT, there are also concerns of information leakage due to all certificates being visible in CT logs. To understand this threat, we introduce a CT honeypot and show that data from CT logs is being used to identify targets for scanning campaigns only minutes after certificate issuance. We present and evaluate a methodology to learn and validate new subdomains from the vast number of domains extracted from CT logged certificates.

Carlos Cateriano Yáñes, Georg Panagalos und Gerwald Lichtenberg
An Approach to linear state Signal Shaping by quadratic Model Predictive Control
European Control Conference
ECC 2018

Marker: LS-MT

Kathrin Weihe, Carlos Cateriano Yáñes, Georg Pangalos und Gerwald Lichtenberg
Comparison of Linear State Signal Shaping Model Predictive Control with Classical Concepts for Active Power Filter Design
8th International Conference on Simulation and Modeling Methodologies, Technologies and Applications (Simultech)

Marker: LS-MT

Andreas Reuter, Randy Bush, Italo Cunha, Ethan Katz-Bassett, Thomas C. Schmidt und Matthias Wählisch
Towards a Rigorous Methodology for Measuring Adoption of RPKI Route Validation and Filtering
Montreal, CA
Proceedings of the Applied Networking Research Workshop aus ANRW '18 , Seite 7--7.
Verlag: ACM Digital Library, New York, NY, USA
ISBN: 978-1-4503-5585-8

Marker: TI-I

Julius Weyl, Daniel Glake und Thomas Clemen
Agent-based Traffic Simulation at City Scale with MARS
Proceedings of the 2018 Spring Simulation Multiconference
Verlag: Society for Computer Simulation International, Baltimore, MD, USA

Schlüsselwörter: agent-based,city scale,traffic

Marker: TI-I

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Letzte Änderung: 23.01.15

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