Adaptive fast open-loop maneuvers for quadrocopters

We present a conceptually and computationally lightweight method for the design and iterative learning of fast maneuvers for quadrocopters. We use first-principles, reduced-order models and we do not require nor make an attempt to follow a specific state trajectory—only the initial and the final states of the vehicle are taken into account. We evaluate the adaptation scheme through experiments on quadrocopters in the ETH Flying Machine Arena that perform multi-flips and other high-performance maneuvers.     

SLM tooling for die casting with conformal cooling channels

The paper reports an experimental study of die-casting dies with conformal cooling fabricated by direct-metal additive techniques. The main objective is to compare the benefits and limitations of the application to what has been widely discussed in literature in the context of plastics injection molding. Selective laser melting was used to fabricate an impression block with conformal cooling channels designed according to part geometry with the aid of process simulation. The tool was used in the manufacture of sample batches of zinc alloy castings after being fitted on an existing die in place of a machined impression block with conventional straight-line cooling channels. Different combinations of process parameters were tested to exploit the improved performance of the cooling system. Test results show that conformal cooling improves the surface finish of castings due to a reduced need of spray cooling, which is allowed by a higher and more uniform cooling rate. Secondary benefits include reduction of cycle time and shrinkage porosity.     

An algorithm for sampling subsets of H/sub /spl infin// with applications to risk-adjusted performance analysis and model (in)validation

In spite of their potential to reduce computational complexity, the use of probabilistic methods in robust control has been mostly limited to parametric uncertainty, since the problem of sampling causal bounded operators is largely open. In this note, we take steps toward removing this limitation by proposing a computationally efficient algorithm aimed at uniformly sampling suitably chosen subsets of H/sub /spl infin//. As we show in the note, samples taken from these sets can be used to carry out model (in)validation and robust performance analysis in the presence of structured dynamic linear time-invariant uncertainty, problems known to be NP-hard in the number of uncertainty blocks.     

∞ optimal interconnections

In this paper a general _∞ problem for continuous time, linear time systems is formulated and solved in a behavioral framework. This general formulation, which includes standard _∞ optimization as a special case, provides added freedom in the design of sub-optimal compensators, and allows for singular interconnections, which naturally occur when interconnecting first principles models. It is shown that a necessary condition for the existence of a solution is the existence of a partition of the control variables which allows one to express the given system by a possibly non-proper, non-standard, input-state-output map. A slight modification of the DGKF Riccati-based solution may then be employed to provide a complete solution. It is shown, with the aid of an example, that the optimal solution may lead to some counter-intuitive constraints which may require novel mechanisms for implementation; thus, the formal optimization techniques being considered in this paper may provide guidelines for design.     

On the peaking phenomenon in the control of vehicular platoons

We investigate the peaking phenomenon in the control of large-scale vehicular platoons. These systems are of considerable practical importance as they represent an example of systems on lattices in which different subsystems are dynamically coupled only through feedback controls. We demonstrate that imposing a uniform rate of convergence for all vehicles towards their desired trajectories may generate large transient peaks in both velocity and control. We further derive explicit constraints on feedback gains–for any given set of initial conditions–to achieve desired position transients without magnitude and rate peaking. These constraints are used to generate the trajectories around which the states of the platoon system are driven towards their desired values without the excessive use of control effort. All results are illustrated using computer simulations of platoons containing a large number of vehicles.     

Generalized Graph k-Coloring Games

Theory of Computing Systems - We investigate pure Nash equilibria in generalized graphk-coloring games where we are given an edge-weighted undirected graph together with a set of k colors. Nodes...     

Filter characterisation using one-port pulsed radio-frequency measurements

A method for extracting the loaded quality factor of the first resonator of a bandpass filter using oneport measurements is introduced. Properties of the quality factor are reviewed, and a time-domain approximation is used to estimate the loaded Q value from the decay rate of the filter?s natural response. Narrowband 900 MHz Chebyshev filters are characterised.     

Occurrence of mycotoxin in Farro samples from southern Italy

The occurrence of nine mycotoxins and of contamination by pre- and postharvest fungal pathogens of cereals was investigated in samples of stored Triticum monococcum L., Triticum dicoccon Schrank (emmer), and Triticum spelta L. (spelt). In Italy, all three species are collectively referred to as farro. The samples examined were harvested in summer 2000 from eight different sites in southern Italy. Conventional fluorimetric and diode array-based high-performance liquid chromatography (HPLC) analyses and HPLC-mass spectrometry analyses were used to identify fumonisin B1 in five samples (up to 70.00 microg/ kg), ochratoxin A in seven samples (up to 4.07 microg/kg), and beauvericin in three samples (up to 4.44 mg/kg). Enniatin B was detected in one sample (30.00 microg/kg), but no zearalenone or fusaproliferin was found. Deoxynivalenol and aflatoxins were not evaluated. The potentially mycotoxigenic fungal species detected were Alternaria alternata, Fusarium proliferatum, Fusarium tricinctum, Penicillium verrucosum, and Penicillium chrysogenum. This is the first report of the natural occurrence of mycotoxins in farro samples.     

Hepatitis C virus and non-Hodgkin's lymphomas

Hepatitis C virus (HCV) seems to be the aetiologic agent of mixed cryoglobulinaemia, and as this 'benign' lymphoproliferative disorder can frequently develop into more aggressive haematological disorders, this study was undertaken to determine the prevalence of HCV infection in non-Hodgkin's lymphomas. 199 unselected subjects treated by three haematological centres in Northeast Italy were investigated for the presence of HCV infection. As controls, the prevalence of HCV infection was determined in a group of patients affected by other haematological malignancies (153 subjects) and in the general population of the same geographical area in the cohort study called the Dyonisos project (6917 subjects). The presence of anti-HCV antibodies was determined by a commercial kit and, in positive cases, by PCR amplification of the 5' untranslated region of the virus. The HCV genotype was also obtained by PCR amplification of the Core region with type-specific primers. The presence of serum cryoglobulins was determined in each case of NHL. HCV infection was significantly (P < 0.00000001) higher in patients with non-Hodgkin's lymphomas (28.0%) when compared with that of the general population (2.9%), and with the group of patients affected by other malignancies (3.1%). The prevalence is particularly high in low-grade (38.4%), as compared with intermediate (11.4%), or high-grade (15.2%) lymphomas. The presence of the virus is significantly (P < 0.000001) associated with the presence of detectable levels of cryoglobulins. On the basis of these findings. HCV seems to play an important role in the development of low-grade non-Hodgkin's lymphomas.