Quadratic programming algorithms for large-scale model predictive control

Quadratic programming (QP) methods are an important element in the application of model predictive control (MPC). As larger and more challenging MPC applications are considered, more attention needs to be focused on the construction and tailoring of efficient QP algorithms. In this study, we tailor and apply a new QP method, called QPSchur, to large MPC applications, such as cross directional control problems in paper machines. Written in C++, QPSchur is an object oriented implementation of a novel dual space, Schur complement algorithm. We compare this approach to three widely applied QP algorithms and show that QPSchur is significantly more efficient (up to two orders of magnitude) than the other algorithms. In addition, detailed simulations are considered that demonstrate the importance of the flexible, object oriented construction of QPSchur, along with additional features for constraint handling, warm starts and partial solution.     

Three 2D-warping schemes for visual robot navigation

Warping (Franz et al., Biological Cybernetics 79(3), 191–202, 1998b) and 2D-warping (Möller, Robotics and Autonomous Systems 57(1), 87–101, 2009) are effective visual homing methods which can be applied for navigation in topological maps. This paper presents several improvements of 2D-warping and introduces two novel “free” warping methods in the same framework. The free warping methods partially lift the assumption of the original warping method that all landmarks have the same distance from the goal location. Experiments on image databases confirm the effect of the improvements of 2D-warping and show that the two free warping methods produce more precise home vectors and approximately the same proportion of erroneous home vectors. In addition, two novel and easier-to-interpret performance measures for the angular error are introduced.     

Integration of Corona and Landsat Thematic Mapper data for bedrock geological studies in the high Arctic

The Severnaya Zemlya Archipelago near the continental edge in the Russian high Arctic is one of few land areas along the Eurasian Arctic margin. It is of particular interest for investigating the Arctic's tectonic history. This study focuses on the Palaeozoic bedrock of October Revolution Island. In the Russian high Arctic detailed topographic maps and aerial photography often are not available. The potential of low-cost satellite imagery as a substitute is shown in this study. High-resolution Corona KH-4A panchromatic satellite imagery and Landsat Thematic Mapper (TM) multispectral data have been integrated. In combination with field investigations in key areas, these data provide the basis for new interpretations of the geology. Corona images were digitized and georeferenced to provide a basis for conventional and digital geological mapping. Merging Corona and Landsat TM data resulted in a high-resolution multispectral image of enhanced interpretability. Lithological contacts have been traced, supported by a bedrock image extracted from the Landsat TM data. Stereoscopic coverage of the Corona KH-4A photographic sensor allowed a structural interpretation. All results were integrated into a geological interpretation of southern October Revolution Island which provides an encouraging platform for further work in the high Arctic.     

Cellular Mechanisms of the Anti-Arrhythmic Effect of Cardiac PDE2 Overexpression

Background: Phosphodiesterases (PDE) critically regulate myocardial cAMP and cGMP levels. PDE2 is stimulated by cGMP to hydrolyze cAMP, mediating a negative crosstalk between both pathways. PDE2 upregulation in heart failure contributes to desensitization to β-adrenergic overstimulation. After isoprenaline (ISO) injections, PDE2 overexpressing mice (PDE2 OE) were protected against ventricular arrhythmia. Here, we investigate the mechanisms underlying the effects of PDE2 OE on susceptibility to arrhythmias. Methods: Cellular arrhythmia, ion currents, and Ca²⁺-sparks were assessed in ventricular cardiomyocytes from PDE2 OE and WT littermates. Results: Under basal conditions, action potential (AP) morphology were similar in PDE2 OE and WT. ISO stimulation significantly increased the incidence of afterdepolarizations and spontaneous APs in WT, which was markedly reduced in PDE2 OE. The ISO-induced increase in I_CaL seen in WT was prevented in PDE2 OE. Moreover, the ISO-induced, Epac- and CaMKII-dependent increase in I_NaL and Ca²⁺-spark frequency was blunted in PDE2 OE, while the effect of direct Epac activation was similar in both groups. Finally, PDE2 inhibition facilitated arrhythmic events in ex vivo perfused WT hearts after reperfusion injury. Conclusion: Higher PDE2 abundance protects against ISO-induced cardiac arrhythmia by preventing the Epac- and CaMKII-mediated increases of cellular triggers. Thus, activating myocardial PDE2 may represent a novel intracellular anti-arrhythmic therapeutic strategy in HF.     

The microstructure of dispersed and non-dispersed fresh cement pastes — New insight by cryo-microscopy

This study aims to give new insights to the microstructural development of fresh cement pastes without and with polycarboxylate-type (PCE) of superplasticizers. Qualitative comparisons of the particulate structure of such cementitious systems were carried out by using cryo-FIB and cryo-SEM techniques. The natural structure of fresh cement pastes was preserved by high pressure freezing.It is illustrated that non-dispersed cement systems tend to form hydration rims on the surface of the clinker grains immediately after mixing. This leads to an interlocking of the particles. In contrast, in the dispersed systems the early hydrates precipitate in the pore solution and thus, agglomeration is prevented. These microstructural observations are important aspects of the fluidization effect of superplasticizers.     

Disturbance Torque and Motion State Estimation With Low-Resolution Position Interfaces Using Heterodyning Observers

This paper assesses and analyzes a harmonic vector modeling method for reducing disturbance torque and motion state estimation error using quantized input measurements of position. There is a finite resolution available for any digital interface, and quantization will always be present in some form. Although it is not possible to completely reconstruct a quantized measured state, it is possible to attenuate deterministic quantization characteristics. The discussed method models quantized position feedback as a spatially rotating vector consisting of fundamental and harmonic components. The error mitigation strategy involves decoupling these spatial quantization harmonics from the actual fundamental position, using heterodyning tracking observer topologies.     

Mechanistic aspects the dioxin (aryl hydrocarbon) receptor

The Ah receptor mediates the toxicological responses of 2,3,7,8-TCDD and related compounds. Receptor-deficient animals were shown to be resistant to the toxic effects of dioxin, although there is also evidence for the existence of a receptor-independent pathway for dioxin-induced toxicity. In the cytosol the receptor is present in a non-activated ligand binding conformation. Association with Arnt in the nucleus turns the receptor complex into a ligand activated form. The physiological role of the receptor is not yet understood; however, the conservation of the receptor in a wide range of animal species (including humans) suggests a fundamental role in cellular physiology.     

Performance measurements on an ATM-based metropolitan area network: OASICE case study

The city of Colmar is developing a Metropolitan Area Network (MAN) called OASICE. Our MAN uses ATM technology to provide a range of business, academic and community tele-services such as tele-teaching, tele-information, tele-documentation, tele-management and tele-surveillance of property, high definition tele-conference, VOD (Video On Demand), etc. This revised version was published online in August 2006 with corrections to the Cover Date.