Electrode reactions of nickel(II) at mercury electrodes in aqueous solutions of pyridine at high ionic strengths

At high ionic strength the ion pair (NiPy²⁺₄, nX^?) or complex (NiPy₄X₂), n = 0, 1, 2; X^? = Cl^?, Br^?, SCN^?, N^?₃, F^?, NO^?₃, ClO^?₄; is adsorbed at the surface of mercury electrode. Under specified conditions in chloride, bromide, and thiocyanates solutions the electroreduction is preceded by a crystallization of a complex on the electrode surface. The inductive role of specifically coadsorbed Cl^? ions is discussed.     

Sensitivity of regions of irregular and chaotic vibrations of an asymmetric rotor supported on journal bearings to structural parameters

Rotating elements supported on journal bearings are widely encountered structures in engineering practice. Most commonly, these are asymmetrically manufactured and loaded rigid rotors transmitting torque and carrying transverse as well as axial forces. Nowadays, despite high operational demands and high rotational velocities, such systems are still expected to exhibit stable working, even in the presence of small assembly deviations, light unbalance or external disturbances. The surrounding environment of a rotating machine may interact with it by kinematic excitation from vibrating foundation. This, in turn, may lead to hazardous response and the onset of irregular and chaotic motion of the rotor. The subject of the study is to find and analyze regions of the occurrence of such vibrations in the system of a rigid rotor supported in journal bearings. The bearings themselves are assumed to be non-perfectly mounted in the housing, i.e., their sleeves are inserted in rings possessing some viscoelastic properties. These properties are treated as variable parameters, and the aim is to move the regions of irregular and chaotic vibration outside the operational regime (angular velocity). The adjustability of the viscoelastic parameters may be realized by incorporation of smart materials such as piezoelectric or magnetorheological ones. The considered system is an asymmetric rigid rotor supported on two journal bearings subject to a steady kinematic excitation. The system is described by eight coupled nonlinear ordinary differential equations of motion. Results of the examinations prove that by selecting an appropriate magnitude of damping and stiffness of the bearing mountings, it is possible to enlarge the region of stable operation of the rotating system and thus secure its safety. This, however, does not mean the elimination of chaotic response at all, but only a shift of it outside the range of operational rotation speed.     

Action rule discovery from incomplete data

Action rule is an implication rule that shows the expected change in a decision value of an object as a result of changes made to some of its conditional values. An example of an action rule is ‘credit card holders of young age are expected to keep their cards for an extended period of time if they receive a movie ticket once a year’. In this case, the decision value is the account status, and the condition value is whether the movie ticket is sent to the customer. The type of action that can be taken by the company is to send out movie tickets to young customers. The conventional action rule discovery algorithms build action rules from existing classification rules. This paper discusses an agglomerative strategy that generates the shortest action rules directly from a decision system. In particular, the algorithm can be used to discover rules from an incomplete decision system where attribute values are partially incomplete. As one of the testing domains for our research we take HEPAR system that was built through a collaboration between the Institute of Biocybernetics and Biomedical Engineering of the Polish Academy of Sciences and physicians at the Medical Center of Postgraduate Education in Warsaw, Poland. HEPAR was designed for gathering and processing clinical data on patients with liver disorders. Action rules will be used to construct the decision-support module for HEPAR.     

Effect of indium on wettability of Sn–Ag–Cu solders. Experiment vs. modeling,Part I

The density and surface tension measurements of the Sn3.13Ag0.74Cu liquid alloys with 2, 3, 4, 15, 30, 50 and 75 at.% In additions were conducted in the temperature range from 431 K up to 1209 K by dilatometric technique and the maximum bubble pressure method, respectively. The results obtained in both techniques exhibited 2%–3% scattering of experimental errors, similarly to the previously investigated In–Sn and Sn–Ag–In systems. This was due to the very similar surface tension and density values of pure indium and tin. The experimental surface tensions were compared with calculated ones using data of the constituent systems, (a) by means of thermodynamic method of Butler, and (b) by the temperature and concentration relation of the surface tension. The improvement of wettability in liquid alloys containing different In additions was confirmed with a sessile drop method in the temperature interval 523 K–593 K up to 1800 s. The wetting angles decreased with temperature and increasing In concentrations in the solders from ∼37^°$\sim 37^{°}$ for the solder without In at 523 K down to ∼22^°$\sim 22^{°}$ for the solder with 75 at.% In at 593 K.     

Linear positive control systems on time scales; controllability

Positive linear systems on arbitrary time scales are studied. The theory developed in the paper unifies and extends concepts and results known for continuous-time and discrete-time systems. A necessary and sufficient condition for a linear system on a time scale to be positive is presented. Properties of positive reachable sets are investigated and characterizations of various controllability properties are presented. A modified Gram matrix of the system is used to state necessary and sufficient condition of positive reachability of a positive system on an arbitrary time scale.     

The mechanical generation of fault trees for reactive systems via retrenchment II: clocked and feedback circuits

The retrenchment approach to the mechanical construction of fault trees, introduced in the first paper for combinational logic circuits, is extended to handle clocked circuits and then feedback circuits. The temporal behaviour of clocked circuits is captured using their causal relations, and the potentially unbounded behaviour of cyclic circuits is decomposed into an iteration over their acyclic counterparts. The repercussions of all this for the theory of retrenchment are elaborated. For clocked circuits, the techniques we present allow glitches and other transient errors to be properly described. For feedback circuits, the plethora of behaviours that can occur, give rise to infinitary fault trees of an appropriate kind. All this paves the way for automated fault tree generation for reactive systems.     

The mechanical generation of fault trees for reactive systems via retrenchment I: combinational circuits

The manual construction of fault trees for complex systems is an error-prone and time-consuming activity, encouraging automated techniques. In this paper we show how the retrenchment approach to formal system model evolution can be developed into a versatile structured approach for the mechanical construction of fault trees. The system structure and the structure of retrenchment concessions interact to generate fault trees with appropriately deep nesting. We show how this approach can be extended to deal with minimisation, thereby diminishing the post hoc subsumption workload and potentially rendering some infeasible cases feasible.     

Multimodal processes optimization subject to fuzzy operation time constraints: declarative modeling approach

We present an extension of the resource-constrained multi-product scheduling problem for an automated guided vehicle (AGV) served flow shop, where multiple material handling transport modes provide movement of work pieces between machining centers in the multimodal transportation network (MTN). The multimodal processes behind the multi-product production flow executed in an MTN can be seen as processes realized by using various local periodically functioning processes. The considered network of repetitively acting local transportation modes encompassing MTN’s structure provides a framework for multimodal processes scheduling treated in terms of optimization of the AGVs fleet scheduling problem subject to fuzzy operation time constraints. In the considered case, both production takt and operation execution time are described by imprecise data. The aim of the paper is to present a constraint propagation (CP) driven approach to multi-robot task allocation providing a prompt service to a set of routine queries stated in both direct and reverse way. Illustrative examples taking into account an uncertain specification of robots and workers operation time are provided.     

Atomic actions, and their refinements to isolated protocols

Inspired by the properties of the refinement development of the Mondex Electronic Purse, we view an isolated atomic action as a family of transitions with a common before-state, and different after-states corresponding to different possible outcomes when the action is attempted. We view a protocol for an atomic action as a computation DAG, each path of which achieves in several steps one of the outcomes of the atomic action. We show that in this picture, the protocol can be viewed as a relational refinement of the atomic action in a number of ways. Firstly, it yields a ‘big diagram’ simulation à la ASM. Secondly, it yields a ‘small diagram’ simulation, in which the atomic action is synchronised with an individual step along each path through the protocol, and all the other steps of the path simulate skip. We show that provided each path through the protocol contains one step synchronised with the atomic action, the choice of synchronisation point can be made freely. We describe the relationship between such synchronisations and forward and backward simulations. We relate this theory to serialisations of system runs containing multiple interleaved transactions, showing how the clean picture of the refinement of an isolated atomic action to an isolated protocol becomes obscured by the details of the interleaving. In effect, the fact that protocols are typically executed by a number of co-operating agents, not all of which embark on executing the protocol at the same moment, results in ‘ragged starts’ and ‘ragged ends’ to protocol instantiations, leading to potential overlaps between unrelated protocol instances that the theory must handle. We show how existing Mondex refinements embody the ideas developed, and describe a mechanical verification of the results presented.