A Secure Infrastructure For System Console and Reset Access

During the last years large farms have been built using commodity hardware. This hardware lacks components for remote and automated administration. Products that can be retrofitted to these systems are either costly or inherently insecure. We present a system based on serial ports and simple machine controlled relays. We report on experience gained by setting up a 50-machine test environment as well as current work in progress in the area.Comment: Conference for Computing in High Energy and Nuclear Physics (CHEP2003), March 24-28, 2003, La Jolla, Californi

The Accuracy of Long-term Real Estate Valuations

By using a unique data set of single-family house transactions, we examine the accuracy of the cost and sales comparison approach over different forecast horizons. We find that sales comparison values provide better long-term forecasts than cost values if the economic loss function is symmetric. A weighted average of both sales comparison value and cost value can reduce this loss even further. If the economic loss function is asymmetric, however, cost values might provide better long-term forecasts.prediction accuracy, mortgage underwriting, risk management

The EU will not be able to enforce the UN arms embargo in Libya

On 19 January 2020 a high-level conference was held in Berlin to find solutions to the conflict in Libya between the unity government under Fayez al-Sarraj and the troops led by General Khalifa Haftar. A central agreement in the final declaration aims to stop the unimpeded influx of weapons that external actors are making available to the warring parties. The conference participants committed themselves to "unequivocally and fully respect and implement the arms embargo established by United Nations Secu­rity Council Resolution 1970 (2011) and the Council's subsequent resolutions, including the proliferation of arms from Libya, and call on all international actors to do the same". The declaration thus reaffirms the existing resolutions, revealing its basic problem: So far, the United Nations (UN) has not been able to effectively enforce the current embargo for a variety of reasons. (author's abstract

Efficient Process-to-Node Mapping Algorithms for Stencil Computations

Good process-to-compute-node mappings can be decisive for well performing HPC applications. A special, important class of process-to-node mapping problems is the problem of mapping processes that communicate in a sparse stencil pattern to Cartesian grids. By thoroughly exploiting the inherently present structure in this type of problem, we devise three novel distributed algorithms that are able to handle arbitrary stencil communication patterns effectively. We analyze the expected performance of our algorithms based on an abstract model of inter- and intra-node communication. An extensive experimental evaluation on several HPC machines shows that our algorithms are up to two orders of magnitude faster in running time than a (sequential) high-quality general graph mapping tool, while obtaining similar results in communication performance. Furthermore, our algorithms also achieve significantly better mapping quality compared to previous state-of-the-art Cartesian grid mapping algorithms. This results in up to a threefold performance improvement of an MPI_Neighbor_alltoall exchange operation. Our new algorithms can be used to implement the MPI_Cart_create functionality.Comment: 18 pages, 9 Figure

Ascertaining the Values of σx\sigma_x, σy\sigma_y, and σz\sigma_z of a Polarization Qubit

In the 1987 spin retrodiction puzzle of Vaidman, Aharonov, and Albert one is challenged to ascertain the values of $\sigma_x$, $\sigma_y$, and $\sigma_z$ of a spin-1/2 particle by utilizing entanglement. We report the experimental realization of a quantum-optical version in which the outcome of an intermediate polarization projection is inferred by exploiting single-photon two-qubit quantum gates. The experimental success probability is consistently above the 90.2% threshold of the optimal one-qubit strategy, with an average success probability of 95.6%.Comment: 4 pages, 2 figures; final version with new title and new abstract; to appear in Physical Review Letter

Categorization and Evaluation Methods for Control Strategies of Bilateral Tasks in Arm Prosthetics

Controlling multi-joint prostheses intuitively and effortlessly has been a research topic since the appearance of the first electric elbow prostheses. Researchers mainly focused on single handed tasks, however in daily life these are mostly executed with the healthy hand and the prosthetic arms only become relevant for two-handed manipulations. Thus, a new approach is presented in this paper addressing bilateral tasks. A taxonomy for bilateral tasks is elaborated in order to categorize and prioritize bilateral manipulations involving a prosthetic arm. Five different key figures for rating bilateral movements are introduced and used to form two quality criteria, which allow evaluation and comparison of different control strategies. Based on the proposed taxonomy and quality criteria, a generalized benchmark test environment is developed with five different evaluation scenarios and realized in virtual reality in an exemplary manner. Furthermore, a new controller-agent strategy, greatly facilitating the usage of prosthetic arms, is presented. The effectiveness of the criteria for evaluation of different control strategies is demonstrated with healthy subjects. With this evaluation concept, we provide the community a means to explore and compare controlling methods and inputs, facilitating the progress and development of new strategies

Dislocation multiplication by cross-slip and glissile reaction in a dislocation based continuum formulation of crystal plasticity

Modeling dislocation multiplication due to interaction and reactions on a mesoscopic scale is an important task for the physically meaningful description of stage II hardening in face centered cubic crystalline materials. In recent Discrete Dislocation Dynamics simulations it is observed that dislocation multiplication is exclusively the result of mechanisms, which involve dislocation reactions between different slip systems. These findings contradict multiplication models in dislocation based continuum theories, in which density increase is related to plastic slip on the same slip system. An application of these models for the density evolution on individual slip systems results in self-replication of dislocation density. We introduce a formulation of dislocation multiplication in a dislocation based continuum formulation of plasticity derived from a mechanism-based homogenization of cross-slip and glissile reactions in three-dimensional face-centered cubic systems. As a key feature, the presented model includes the generation of dislocations based on an interplay of dislocation density on different slip systems. This particularly includes slip systems with vanishing shear stress. The results show, that the proposed dislocation multiplication formulation allows for a physically meaningful microstructural evolution without self-replication of dislocations density. The results are discussed in comparison to discrete dislocation dynamics simulations exposing the coupling of different slip systems as the central characteristic for the increase of dislocation density on active and inactive slip systems. (C) 2019 Elsevier Ltd. All rights reserved

Empirical approach for the residual flexural tensile strength of steel fiber-reinforced concrete based on notched three-point bending tests

When designing steel fiber-reinforced concrete, for example, according to Model Code 2010, the residual flexural strength values must be specified as fundamental properties. It is often difficult to establish the relationship between residual flexural strength values and the required dosage of steel fibers depending on the type of steel fibers and the concrete quality. For an estimation of the presumably necessary dosage of steel fibers, various empirical approaches exist for the approximate determination of the residual flexural strength values, which, however, are based on different tests and have been almost exclusively been derived on the basis of few or “own” test results of the respective institute. For this reason, the validity of the respective approximation approach is often limited. Using the bending beam database “Steel Fibre Reinforced Concrete”, selected approaches were systematically analyzed and an improved approach for determining the residual flexural strength values of steel fiber-reinforced concrete was developed

Categorization and Evaluation Methods for Control Strategies of Bilateral Tasks in Arm Prosthetics

Controlling multi-joint prostheses intuitively and effortlessly has been a research topic since the appearance of the first electric elbow prostheses. Researchers mainly focused on single handed tasks, however in daily life these are mostly executed with the healthy hand and the prosthetic arms only become relevant for two-handed manipulations. Thus, a new approach is presented in this paper addressing bilateral tasks. A taxonomy for bilateral tasks is elaborated in order to categorize and prioritize bilateral manipulations involving a prosthetic arm. Five different key figures for rating bilateral movements are introduced and used to form two quality criteria, which allow evaluation and comparison of different control strategies. Based on the proposed taxonomy and quality criteria, a generalized benchmark test environment is developed with five different evaluation scenarios and realized in virtual reality in an exemplary manner. Furthermore, a new controller-agent strategy, greatly facilitating the usage of prosthetic arms, is presented. The effectiveness of the criteria for evaluation of different control strategies is demonstrated with healthy subjects. With this evaluation concept, we provide the community a means to explore and compare controlling methods and inputs, facilitating the progress and development of new strategies

High energy astroparticle physics for high school students

The questions about the origin and type of cosmic particles are not only fascinating for scientists in astrophysics, but also for young enthusiastic high school students. To familiarize them with research in astroparticle physics, the Pierre Auger Collaboration agreed to make 1% of its data publicly available. The Pierre Auger Observatory investigates cosmic rays at the highest energies and consists of more than 1600 water Cherenkov detectors, located near Malarg\"{u}e, Argentina. With publicly available data from the experiment, students can perform their own hands-on analysis. In the framework of a so-called Astroparticle Masterclass organized alongside the context of the German outreach network Netzwerk Teilchenwelt, students get a valuable insight into cosmic ray physics and scientific research concepts. We present the project and experiences with students.Comment: 8 pages, 5 figures, Proceedings of the 34th International Cosmic Ray Conference (ICRC2015), The Hague, The Netherlands, PoS(ICRC2015)30