Testing validation tools on CLIPS-based expert systems

The Expert Systems Validation Associate (EVA) is a validation system which was developed at the Lockheed Software Technology Center and Artificial Intelligence Center between 1986 and 1990. EVA is an integrated set of generic tools to validate any knowledge-based system written in any expert system shell such as C Language Integrated Production System (CLIPS), ART, OPS5, KEE, and others. Many validation tools have been built in the EVA system. In this paper, we describe the testing results of applying the EVA validation tools to the Manned Maneuvering Unit (MMU) Fault Diagnosis, Isolation, and Reconfiguration (FDIR) expert system, written in CLIPS, obtained from the NASA Johnson Space Center

Building validation tools for knowledge-based systems

The Expert Systems Validation Associate (EVA), a validation system under development at the Lockheed Artificial Intelligence Center for more than a year, provides a wide range of validation tools to check the correctness, consistency and completeness of a knowledge-based system. A declarative meta-language (higher-order language), is used to create a generic version of EVA to validate applications written in arbitrary expert system shells. The architecture and functionality of EVA are presented. The functionality includes Structure Check, Logic Check, Extended Structure Check (using semantic information), Extended Logic Check, Semantic Check, Omission Check, Rule Refinement, Control Check, Test Case Generation, Error Localization, and Behavior Verification

On dispersive energy transport and relaxation in the hopping regime

A new method for investigating relaxation phenomena for charge carriers hopping between localized tail states has been developed. It allows us to consider both charge and energy {\it dispersive} transport. The method is based on the idea of quasi-elasticity: the typical energy loss during a hop is much less than all other characteristic energies. We have investigated two models with different density of states energy dependencies with our method. In general, we have found that the motion of a packet in energy space is affected by two competing tendencies. First, there is a packet broadening, i.e. the dispersive energy transport. Second, there is a narrowing of the packet, if the density of states is depleting with decreasing energy. It is the interplay of these two tendencies that determines the overall evolution. If the density of states is constant, only broadening exists. In this case a packet in energy space evolves into Gaussian one, moving with constant drift velocity and mean square deviation increasing linearly in time. If the density of states depletes exponentially with decreasing energy, the motion of the packet tremendously slows down with time. For large times the mean square deviation of the packet becomes constant, so that the motion of the packet is ``soliton-like''.Comment: 26 pages, RevTeX, 10 EPS figures, submitted to Phys. Rev.

The management of acute venous thromboembolism in clinical practice. Results from the European PREFER in VTE Registry

Venous thromboembolism (VTE) is a significant cause of morbidity and mortality in Europe. Data from real-world registries are necessary, as clinical trials do not represent the full spectrum of VTE patients seen in clinical practice. We aimed to document the epidemiology, management and outcomes of VTE using data from a large, observational database. PREFER in VTE was an international, non-interventional disease registry conducted between January 2013 and July 2015 in primary and secondary care across seven European countries. Consecutive patients with acute VTE were documented and followed up over 12 months. PREFER in VTE included 3,455 patients with a mean age of 60.8 ± 17.0 years. Overall, 53.0 % were male. The majority of patients were assessed in the hospital setting as inpatients or outpatients (78.5 %). The diagnosis was deep-vein thrombosis (DVT) in 59.5 % and pulmonary embolism (PE) in 40.5 %. The most common comorbidities were the various types of cardiovascular disease (excluding hypertension; 45.5 %), hypertension (42.3 %) and dyslipidaemia (21.1 %). Following the index VTE, a large proportion of patients received initial therapy with heparin (73.2 %), almost half received a vitamin K antagonist (48.7 %) and nearly a quarter received a DOAC (24.5 %). Almost a quarter of all presentations were for recurrent VTE, with >80 % of previous episodes having occurred more than 12 months prior to baseline. In conclusion, PREFER in VTE has provided contemporary insights into VTE patients and their real-world management, including their baseline characteristics, risk factors, disease history, symptoms and signs, initial therapy and outcomes

Elektronische Eigenschaften und Struktur amorpher Halbleiter als Basismaterialien fuer Solarzellen Schlussbericht

This report describes results of investigations of physical properties of amorphous semiconductors (a-Si:H, alloys a-Si_1_-_xGe_x:H, a-SiN_x:H, a-Si_1_-_xC_x:H). Both films and devices are studied and the addressed questions derive from problems of the development of solar cells: Structure and electronic properties, transport and recombination, characterization of defects, density and energy distribution of defect states, stability of material properties and devices. The general picture can be summarized as follows. Silicon dangling bonds are the dominant defects limiting as recombination centers the carrier lifetimes. Their density and energy distribution can be described in terms of an intrinsic equilibrium process in which weak bonds are broken to form defects. In this model the slope of the valence-band tail (Urbach energy) is the relevant material parameter. It is a characteristic feature of this model that the defect structure is strongly determined by the position of the Fermi level. Extended light exposure causes a metastable increase of the defect density to typically 10"1"7 cm"-"3. In compensated material there is in addition to the defect creation a metastable change of the doping efficiency. Metastable defects are also generated in the accumulation layer of thin-film transistors made from a-Si:H/a-SiN_x both in the n- and p-channel. Details of the recombination mechanism were obtained from measurements of the optically and electrically detected magnetic resonance (ODMR and EDMR). (orig.)Der Bericht beschreibt Ergebnisse der Untersuchung von physikalischen Eigenschaften amorpher Halbleiterfilme (a-Si:H und Legierungen a-Si_1_-_xGe_x:H, a-SiN_x:H und a-Si_1_-_xC_x:H) und daraus aufgebauten Bauelementen. Die Fragestellungen ergeben sich direkt aus der Funktion von Solarzellen wie z.B. Struktur und elektronische Eigenschaften, Ladungstransport und Rekombination, Defektstruktur, Dichte und energetische Verteilung der Defektzustaende, Stabilitaet und Materialeigenschaften und Bauelementen. Zusammengefasst ergibt sich das folgende Bild. Nicht-abgesaettigte Bindungen (dangling bonds) sind in a-Si:H die dominanten Defekte, die als Rekombinationszentren die Lebensdauern begrenzen. Ihre Dichte und energetische Verteilung wird durch einen intrinsischen Gleichgewichtsprozess bestimmt, bei dem schwache Bindungen in Defekte umgewandelt werden. Fuer die Filmqualitaet wird in dieser Vorstellung die Steigung des Valenzbandauslaeufers (Urbachenergie) zum entscheidenden Materialparameter und die Defektstruktur wird durch die Lage der Fermi-Energie bestimmt. Laengere Belichtung fuehrt zu einer Erhoehung der Defektdichte auf Werte von typisch 10"1"7 cm"-"3. In kompensiertem Material aendert die Belichtung zusaetzlich die Dotiereffizienz. Metastabile Defekte treten auch in der Anreicherungsrandschicht von Transistoren aus a-Si:H/a-SiN_x:H sowohl bei n-als auch bei p-leitendem Kanal auf. Details der Rekombinationsprozesse ergeben sich aus Messungen der optisch oder elektrisch detektierten magnetischen Resonanz (ODMR bzw. EDMR). (orig.)SIGLEAvailable from TIB Hannover: F93B1395+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Forschung und Technologie (BMFT), Bonn (Germany)DEGerman