A Framework for the Verification of Certifying Computations

Formal verification of complex algorithms is challenging. Verifying their implementations goes beyond the state of the art of current automatic verification tools and usually involves intricate mathematical theorems. Certifying algorithms compute in addition to each output a witness certifying that the output is correct. A checker for such a witness is usually much simpler than the original algorithm—yet it is all the user has to trust. The verification of checkers is feasible with current tools and leads to computations that can be completely trusted. We describe a framework to seamlessly verify certifying computations. We use the automatic verifier VCC for establishing the correctness of the checker and the interactive theorem prover Isabelle/HOL for high-level mathematical properties of algorithms. We demonstrate the effectiveness of our approach by presenting the verification of typical examples of the industrial-level and widespread algorithmic library LEDA.     

Autonomous stair-climbing with miniature jumping robots.

The problem of vision-guided control of miniature mobile robots is investigated. Untethered mobile robots with small physical dimensions of around 10 cm or less do not permit powerful onboard computers because of size and power constraints. These challenges have, in the past, reduced the functionality of such devices to that of a complex remote control vehicle with fancy sensors. With the help of a computationally more powerful entity such as a larger companion robot, the control loop can be closed. Using the miniature robot's video transmission or that of an observer to localize it in the world, control commands can be computed and relayed to the inept robot. The result is a system that exhibits autonomous capabilities. The framework presented here solves the problem of climbing stairs with the miniature Scout robot. The robot's unique locomotion mode, the jump, is employed to hop one step at a time. Methods for externally tracking the Scout are developed. A large number of real-world experiments are conducted and the results discussed.     

A novel approach to piecewise analytic agricultural machinery path reconstruction

Before analysing machinery operation in fields, it has to be coped with the problem that the GPS signals of GPS receivers located on the machines contain measurement noise, are time-discrete, and the underlying physical system describing the positions, axial and absolute velocities, angular rates and angular orientation of the operating machines during the whole working time are unknown. This research work presents a new three-dimensional mathematical approach using kinematic relations based on control variables as Euler angular velocities and angles and a discrete target control problem, such that the state control function is given by the sum of squared residuals involving the state and control variables to get such a physical system, which yields a noise-free and piecewise analytic representation of the positions, velocities, angular rates and angular orientation. It can be used for a further detailed study and analysis of the problem of why agricultural vehicles operate in practice as they do.     

The influence of business strategy on project portfolio management and its success — A conceptual framework

Firms are facing more difficulties with the implementation of strategies than with its formulation. Therefore, this paper examines the linkage between business strategy, project portfolio management, and business success to close the gap between strategy formulation and implementation. Earlier research has found some supporting evidence of a positive relationship between isolated concepts, but so far there is no coherent and integral framework covering the whole cycle from strategy to success. Therefore, the existing research on project portfolio management is extended by the concept of strategic orientation. Based on a literature review, a comprehensive conceptual model considering strategic orientation, project portfolio structuring, project portfolio success, and business success is developed. This model can be used for future empirical research on the influence of strategy on project portfolio management and its success. Furthermore, it can easily be extended e.g. by contextual factors.     

Automated DNA preparation from maize tissues and food samples suitable for real-time PCR detection of native genes

There is an increasing need for high-throughput analyses of plants and food samples for the presence of specific DNA sequences, e.g. transgenic contaminations. We developed and optimized conditions for the automated isolation of DNA from several maize tissues and various edibles containing maize using the MagNA Pure LC system (Roche Applied Science). Our results show that the system provided is capable of isolating DNA from any tested source. Quantification of an endogenous gene by LightCycler real-time PCR revealed that the DNA is suitable in quality and quantity for multiple PCR analyses.     

Finite and spectral cell method for wave propagation in heterogeneous materials

In the current paper we present a fast, reliable technique for simulating wave propagation in complex structures made of heterogeneous materials. The proposed approach, the spectral cell method, is a combination of the finite cell method and the spectral element method that significantly lowers preprocessing and computational expenditure. The spectral cell method takes advantage of explicit time-integration schemes coupled with a diagonal mass matrix to reduce the time spent on solving the equation system. By employing a fictitious domain approach, this method also helps to eliminate some of the difficulties associated with mesh generation. Besides introducing a proper, specific mass lumping technique, we also study the performance of the low-order and high-order versions of this approach based on several numerical examples. Our results show that the high-order version of the spectral cell method together requires less memory storage and less CPU time than other possible versions, when combined simultaneously with explicit time-integration algorithms. Moreover, as the implementation of the proposed method in available finite element programs is straightforward, these properties turn the method into a viable tool for practical applications such as structural health monitoring [1–3], quantitative ultrasound applications [4], or the active control of vibrations and noise [5, 6].     

Measuring spatial variations of weak layer and slab properties with regard to snow slope stability

Spatial variations of weak layer and slab properties are believed to affect snow slope stability. To quantify spatial variability at the slope scale, penetration resistance was measured with a high-resolution snow micro-penetrometer (SMP) in a partly randomized grid pattern. The grid design consisted of 46 SMP measurement locations. In addition, a full snow profile and 20 compression tests as well as a Rutschblock test at the snow profile location were performed within the grid. Fifteen slopes of different aspects were sampled of which 11 could be analysed. Weak layer and slab properties were characterised using non-spatial as well as spatial statistics and results were related to slope stability. The geostatistical analysis revealed that in more than half of the cases a range could be determined. Slab layers tended to have more spatial structure than the weak layer. Though some trends are apparent, firm conclusions on the dependence of slope stability on spatial variations were not possible due to the limited range of snow conditions in the dataset, and the fact that the definition of slope stability remains elusive. Based on our limited data set, we can therefore not specify the conditions when spatial variations of weak layer and slab properties are most relevant for snow slab release.