Application of Hierarchical Colored Petri Nets for Technological Facilities’ Maintenance Process Evaluation

The high reliability of modern engineering systems is achieved by performing predictive maintenance. Mathematical models based on stochastic timed colored Petri nets are an effective tool for developing complex production processes for Industry 4.0. This article discusses the maintainability evaluation used in hierarchical Petri net models. The hierarchical simulation model was built using timed colored Petri nets, and was constructed with four levels of repair and maintenance modules. New module structures are proposed for simulating the schedule of production tasks and interaction with technological units. The emphasis is on the processes of predicting maintenance and repair, moving units to service, replacing units, and forming a reserve. The design of the simulation modules allows the setting of probabilistic parameters for the distributions of equipment failures, requests for unit maintenance, repair time, and recovery time after repair. The article proposes to use the hierarchical Petri model in conjunction with solving the problem of minimizing the cost of service. The iterative procedure consists of obtaining an approximate unit distribution by tasks, subsequent simulation of the technological process, and adjusting the optimization problem constraints. For example, the hierarchical Petri net is considered to assess the maintainability of autonomous agricultural vehicles. The results of the simulation experiments are presented. A simulation of the agrotechnical production process was performed, during which vehicles were maneuvered, taken out for repair or maintenance, and returned to the reserve fund. The interdependencies of preventive maintenance periods, service operations, failure rates, and predictive maintenance requests were obtained in order to comply with the task scheduling. The proposed model is a generalization, but it is especially effective in studying mobile equipment servicing.

Structure of the Fc fragment of the NIST reference antibody RM8671

As the link between antigen binding and immune activation, the antibody Fc region has received extensive structural study. In this report, the structure of the Fc fragment of the NIST IgG1 mAb (reference material 8671) is described at 2.1 Å resolution in space group P212121, with approximate unit-cell parameters a = 50, b = 80, c = 138 Å. Prior Fc structures with a wide variety of modifications are also surveyed, focusing on those in the same crystal form. To facilitate the analysis of conformations, a reference frame and a two-parameter metric are proposed, considering the CH2 domains as mobile with respect to a fixed dimeric CH3 core. Over several human Fc structures, a significant variation in Fc elbow conformations is observed, which may serve to facilitate the regulation of Fc effector signaling.

On Extensions of Stably FiniteC*-Algebras (II)

For any C*-algebra A with an approximate unit of projections, there is a smallest ideal I of A such that the quotient A/I is stably finite. In this paper a sufficient and necessary condition for an ideal of a C*-algebra with real rank zero to be this smallest ideal is obtained by using K-theory

The Simulation Research of New Induction Heating Power

Along with the maturity of power electronic technology continuously, induction heating technology with its many advantages has been widely used and developed rapidly. However, due to the disadvantages of series resonant induction heating power, such as low input power factor, great grid pollution, it will bring many hazards. This article will make induction heating power network-side input power factor approximate unit power factor with using Active power factor correction technique, and it makes the net side current and voltage be same phase standard sine wave , reduces the network pollution; and with using DC chopper circuit to complete the adjustment of DC voltage, it achieves induction heating power changes. At the same time, using Matlab software for modeling and simulation analysis on the main circuit and control circuit, the simulation results comply with the design requirements and verify the feasibility of the system design.

Interphase Energies and Nonequilibrium Growth of γ-precipitates in Al-Ag: A DFT Study

Density-functional theory (DFT) calculations of interphase boundary energies provide useful input for many precipitate growth models in alloy systems [1]. One example is Al-Ag, where a rich variety of precipitate types exist, and the sizes and shapes are determined roughly by a Wulff construction, namely, minimizing surface free energies with respect to geometry. This is only a first approximation, however, as kinetic-considerations and crystallography do not allow for a uniform, isotropic growth. Consequently, a nonequilibrium growth model is developed for γ-plates [2], which attempts to connect semi-coherent (ledge) and incoherent (edge) interface growth rates in a way that incorporates shape and interface energies. Through this connection, we make a DFT model with approximate unit cells that mirror experimental conditions, which gives accurate predictions for precipitate aspect ratios and time-development of nonequilibrium shapes. Starting from an explicit calculation of Suzuki segregation of solute to stacking-faults, we find a mechanism for nucleation of nanoscale γ-plates on quenched defects, identify a bulk structure from a calculated phase diagram that gives the relevant HCP equilibrium precipitate structure occurring at 50 at.% Ag and calculate critical nucleation parameters for γ-precipitate formation. Applications to island-coarsening and lath morphology are also discussed.

Ideals with bounded approximate units in L1-algebras of locally compact groups

We show that for an arbitrary locally compact group G and for E in a certain class of closed subsets of the primitive ideal space of L1(G), the kernel k(E) has a bounded approximate unit. This generalizes some well-known previous results.

ON ASYMPTOTIC INFERENCE IN COINTEGRATED TIME SERIES WITH FRACTIONALLY INTEGRATED ERRORS

Vector valued autoregressive models with fractionally integrated errors are considered. The possibility of the coefficient matrix of the model having eigenvalues with absolute values equal or close to unity is included. Quadratic approximation to the log-likelihood ratios in the vicinity of auxiliary estimators of the parameters is obtained and used to make a rough identification of the approximate unit eigenvalues, including complex ones, together with their multiplicities. Using the identification thus obtained, the stationary linear combinations (cointegrating relationships) and the trends that induce the nonstationarity are identified, and Wald-type inference procedures for the parameters associated with them are constructed. As in the situation in which the errors are independent and identically distributed (i.i.d.), the limiting behaviors are nonstandard in the sense that they are neither normal nor mixed normal. In addition, the ordinary least squares procedure, which works reasonably well in the i.i.d. errors case, becomes severely handicapped to adapt itself approximately to the underlying model structure, and hence its behavior is significantly inferior in many ways to the procedures obtained here.