Reliability and performance evaluation of systems containing embedded rule-based expert systems

A method for evaluating the reliability of real-time systems containing embedded rule-based expert systems is proposed and investigated. It is a three stage technique that addresses the impact of knowledge-base uncertainties on the performance of expert systems. In the first stage, a Markov reliability model of the system is developed which identifies the key performance parameters of the expert system. In the second stage, the evaluation method is used to determine the values of the expert system's key performance parameters. The performance parameters can be evaluated directly by using a probabilistic model of uncertainties in the knowledge-base or by using sensitivity analyses. In the third and final state, the performance parameters of the expert system are combined with performance parameters for other system components and subsystems to evaluate the reliability and performance of the complete system. The evaluation method is demonstrated in the context of a simple expert system used to supervise the performances of an FDI algorithm associated with an aircraft longitudinal flight-control system

Expected and unexpected products of reactions of 2-hydrazinylbenzothiazole with 3-nitrobenzenesulfonyl chloride in different solvents

Acknowledgements We thank the EPSRC National Crystallography Service (University of Southampton) for the X-ray data collections. Funding information MVNdS and JLW thank CNPq (Brazil) for financial support.Peer reviewedPublisher PD

Different hydrogen-bonded chains in the crystal structures of three alkyl N-[(E )-1-(2-benzylidene-1-methylhydrazinyl)-3- hydroxy-1-oxopropan-2-yl]carbamates

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Coronal Magnetic Structure of Earthbound CMEs and In Situ Comparison

Predicting the magnetic field within an Earth-directed coronal mass ejection (CME) well before its arrival at Earth is one of the most important issues in space weather research. In this article, we compare the intrinsic flux rope type, that is, the CME orientation and handedness during eruption, with the in situ flux rope type for 20 CME events that have been uniquely linked from Sun to Earth through heliospheric imaging. Our study shows that the intrinsic flux rope type can be estimated for CMEs originating from different source regions using a combination of indirect proxies. We find that only 20% of the events studied match strictly between the intrinsic and in situ flux rope types. The percentage rises to 55% when intermediate cases (where the orientation at the Sun and/or in situ is close to 45 degrees) are considered as a match. We also determine the change in the flux rope tilt angle between the Sun and Earth. For the majority of the cases, the rotation is several tens of degrees, while 35% of the events change by more than 90 degrees. While occasionally the intrinsic flux rope type is a good proxy for the magnetic structure impacting Earth, our study highlights the importance of capturing the CME evolution for space weather forecasting purposes. Moreover, we emphasize that determination of the intrinsic flux rope type is a crucial input for CME forecasting models. Plain Language Summary Coronal mass ejections (CMEs) are huge eruptions from the Sun that can cause myriad of space weather effects at Earth. The ability of a CME to drive a geomagnetic storm is given largely by how its magnetic field is configured. Predicting the magnetic structure well before CME arrival at Earth is one of the major goals in space weather forecasting. Palmerio et al. (2018) study 20 CMEs observed both at the Sun and at Earth. They use observations of the solar disc to determine the magnetic structure at the Sun and then compare it with the magnetic structure estimated via magnetic field measurements near Earth. They report that the magnetic structures match closely only in 20% of the events studied. They also estimate the orientations of the CME axes at the Sun and at Earth. They find that 65% of the events change their orientations by less than 90 degrees. They conclude that knowledge of the CME magnetic structure at the Sun is an important factor in space weather forecasting, but the CME evolution after eruption has to be taken into account in order to improve current predictions.Peer reviewe

Different conformations and packing motifs in the crystal structures of four thiophene--carbohydrazide--pyridine derivatives

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Different packing motifs of isomeric (E)-N1-(halophenylmethylidene)-N-methyl-2-(thiophen-2-yl)-acetohydrazides controlled by C—HO interactions

We thank the EPSRC National Crystallography Service (University of Southampton) for the X-ray data collectionsPeer reviewedPublisher PD

Different packing motifs mediated by weak inter­actions and polymorphism in the crystal structures of five 2-(benzyl­­idene)benzosuberone derivatives

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fac-(2-Amido­ethyl-κ2 C 1,O)aqua­tri­chlorido­tin(IV) 1,4,7,10,13,16-hexa­oxacyclo­octa­decane (2/1)

The asymmetric unit of the title compound, [Sn(C3H6NO)Cl3(H2O)]2·C12H24O6, comprises a six-coordinate tin complex and a 18-crown-6 mol­ecule, the latter disposed about a centre of inversion. The tin atom is coordinated by three Cl atoms, that define a facial arrangement, a chelating C-,O- ligand, and a water mol­ecule. The resulting CCl3O2 donor set defines a distorted octa­hedral geometry. The tin-bound aqua ligand forms O—H⋯O hydrogen bonds to the centrosymmetric 18-crown-6 mol­ecule, resulting in a tri-mol­ecular aggregate. These assemble into a supra­molecular chain along the a axis being connected by N—H⋯O hydrogen bonds

(E)-1-Phenyl-2-({5-[(1E)-(2-phenyl­hydrazin-1-yl­idene)meth­yl]-2-thien­yl}methyl­idene)hydrazine

The title mol­ecule, C18H16N4S, adopts a U-shape with the aromatic groups lying syn and orientated in the same direction as the thio­phene S atom. The conformation about each of the C=N bonds is E. Overall, the mol­ecule is curved as seen in the dihedral angle of 30.26 (19)° formed between the terminal benzene rings. In the crystal, supra­molecular chains along the c axis are formed by a combination of N—H⋯N hydrogen bonds and N—H⋯π inter­actions

Collaborative development of remote electronics laboratories in the ELVIS ilab

Remote laboratories represent a significant value to engineering curricula in a variety of cases. Whether it is a complement to a hands-on experience or a substitute when a traditional lab is not feasible, remote laboratories can be a valuable educational resource. Since 1998, the MIT iLab Project has worked to increase the quality and availability of remote laboratories. Using the iLab Shared Architecture, developers of new labs can leverage a set of generic support functions and then share those labs easily and with minimal administrative cost. More recently, the iLab Project, in partnership with Obafemi Awolowo University in Nigeria, Makerere University in Uganda and the University of Dar-es-Salaam in Tanzania and in coordination with the Maricopa Advanced Technology Education Center (MATEC), has focused on building iLabs around the National Instruments Educational Laboratory Virtual Instrumentation Suite (ELVIS) platform. The ELVIS is a low-cost, small-footprint unit that contains most of the common test instruments found in a typical electrical engineering lab. By coupling the ELVIS with iLabs, a variety of remote electronics laboratories can be built and shared around the world. Using this common hardware/software platform, participants in the iLab Project at different levels of the educational spectrum have developed experiments that meet their individual curricular needs and are able to host them for use by other peer institutions. Not only does this increase the variety of ELVISbased iLabs, but it also spurs the creation of teams that can then build other, more diverse iLabs and substantively participate in project-wide collaborative development efforts. Through such coordinated efforts, iLabs can provide rich practical experiences for studentsMaricopa County Community College District. Maricopa Advanced Technology Education CenterCarnegie Corporation of New YorkMicrosoft CorporationNational Science Foundation (U.S.) (award 0702735)Singapore-MIT Alliance for Research and Technology Cente