Interval identification of FMR parameters for spin reorientation transition in (Ga,Mn)As

In this work we report results of ferromagnetic resonance studies of a 6% 15 nm (Ga,Mn)As layer, deposited on (001)-oriented GaAs. The measurements were performed with in-plane oriented magnetic field, in the temperature range between 5K and 120K. We observe a temperature induced reorientation of the effective in-plane easy axis from [-110] to [110] direction close to the Curie temperature. The behavior of magnetization is described by anisotropy fields, H_{eff} (= 4\piM -H_{2\perp}), H_{2\parallel}, and H_{4\parallel}. In order to precisely investigate this reorientation, numerical values of anisotropy fields have been determined using powerful - but still largely unknown - interval calculations. In simulation mode this approach makes possible to find all the resonance fields for arbitrarily oriented sample, which is generally intractable analytically. In 'fitting' mode we effectively utilize full experimental information, not only those measurements performed in special, distinguished directions, to reliably estimate the values of important physical parameters as well as their uncertainties and correlations.Comment: 3 pages, 3 figures. Presented at The European Conference "Physics of Magnetism 2011" (PM'11), June 27 - July 1, 2011, Poznan, Polan

Table-driven analyses in the SPICE-PAC circuit simulation package

Recent applications of SPICE-PAC to transistor parameter extraction and hierarchical simulation require rather flexible circuit analyses, performed for irregularly distributed values of independent variables. An implementation of table-driven analyses (DC, AC, and time-domain) is described in which tables of arbitrarily distributed independent variables (voltages, frequencies, or timepoints) are used rather than the fixed-step strategy implemented in SPICE-like simulators. Simple examples are used to illustrate applications of table-driven analyses. The simple example of MOS inverter modeling shows that data-driven elements can provide the accuracy needed in practical applications, while reducing significantly the computational effort required for evaluation of complex models of semiconductor device

Siphon-Based Verification of Component Compatibility

In component-based systems, two interacting components are compatible if any sequence of services requested by one component can be provided by the other. This concept of compatibility can easily be extended to a set of interacting components. Checking the compatibility of interacting components is essential for any dependable software system. Recently, an approach to verification of component compatibility has been proposed in which the behavior of individual components (at component interfaces) was modeled by labeled Petri nets. Moreover, the composition of interacting components was designed in such a way that all component incompatibilities were manifested by deadlocks in the composed model. Consequently, the verification of component compatibility is performed by deadlock analysis of the composed model. One of techniques for deadlock analysis is based on net structures called siphons. Siphon-based verification of component compatibility is the subject of this paper

STRUCTURAL METHODS IN PERFORMANCE ANALYSIS OF DISCRETE-EVENT SYSTEMS

Timed Petri nets, a formalism developed specifically for representation of concurrent activities, are popular models of discrete-event system. For net models which can be decomposed into simple cyclic subnets, the performance can be determined on the basis of components, without the exhaustive analysis of the behavior of the whole system; such an approach is known as structural analysis. The paper overviews the formal basic concepts of structural methods and uses manufacturing cells as an illustration of structural analysis

Hierarchical derivation of Petri net models of composite schedules for manufacturing cells

Composite schedules for manufacturing cells (or robotic cells) are schedules in which several parts enter and leave the cell in each cycle (although the parts which leave the cell are not necessarily the same as the ones that enter the cell). It appears that composite schedules can easily be transformed into timed Petri net models in which the timed transitions represent the actions (including the durations) of the robot and the machines of the cell. Moreover such models can be derived using stepwise refinements of net models. Hierarchical modeling is obtained by systematic application of the refinement steps

Circuit decompilation in the SPICE-PAC package of simulation subroutines

SPICE-PAC is a package of simulation subroutines ob- tained by redesigning the popular SPICE circuit simulator from University of California at Berkeley. The package is compatible with the SPICE program but also provides several extensions, e.g., it supports circuit variables, contains an interface to hierarchical libraries of standard designs, etc. Recently, the package has been extended by decompilation procedures to provide symbolic description of circuits refined during interactive analyses, or modified by circuit optimization programs

Parameterized subcircuits in the SPICE-PAC package of simulation subroutines

SPICE-PAC is a package of simulation subroutines which is upward compatible with the popular SPICE- 2G circuit simulator, i.e., SPICE-PAC accepts SPICE data files and performs the same analyses, but also provides a number of extensions, for example, it sup- ports circuit variables, contains an interface to libraries of standard designs, and allows to enhance the package capabilities by user defined procedures. Param- eterized subcircuits generalize the original concept of subcircuits; each parameterized invocation contains a list of substitutions performed during subcircuit ex- pansion. The original requirement of strictly identical subcircuits is thus relaxed to subcircuits with identical topology

FIT-S, a simulation-based data-driven parameter extraction program

FIT–S is an interactive program for extraction of device parameters for SPICE–like circuit simulators. It is based on a circuit simulator rather than an explicit set of model equations. Basic advantages of the proposed approach include: (1) explicit model equations need not be known as they are provided by the circuit simulation tool used, (2) fitting can be performed not only for single devices but for functional blocks or whole circuits as well, and (3) the same extractor can be used for a variety of devices and/or device models. The extractor supports numerical as well as symbolic simulation so repeated analyses of linearized circuit (for frequency domain analyses) can be performed very efficiently using the symbolic functions generated from the Coates flowgraph representation of the circuit. Several optimization methods are built into the program to provide robust as well as efficient fitting of device characteristics. Flexibility of the approach is obtained by specification of extraction details in the data sets rather than the extraction procedure. Parameter extraction for heterojunction bipolar transistors (HBT) is used as an illustration of FIT–S capabilities

Modified M-timed Petri nets in modelling and performance evaluation of systems

Modified M-timed Petri nets are Petri nets with exponentially distributed firing times and with generalized inhibitor arcs to interrupt firing transitions. It is shown that the behavior of modified free-choice M-timed Petri nets can be represented by probabilistic state graphs, stationary probabilities of states can thus be obtained by standard techniques used for analysis of continuous-time homogeneous Markov chains. An immediate application of such a model is performance analysis of queueing systems with exponentially distributed service and interarrival times, and with priority and/or preemptive scheduling disciplines. Simple models of computer systems with different scheduling strategies are used as an illustration of modelling and performance analysis

Performance evaluation using unbounded timed Petri nets

Unbounded timed Petri nets are place-unbounded free-choice place/transition nets with exponentially distributed firing times associated with transitions of a net. In such nets the finite state space is generated by a finite set of linear equations. The regularity of this linear description can be used for a 'projection' (or 'folding') of the infinite state space into an equivalent finite representation that can be described by a finite set of nonlinear equilibrium equations. The solution of these equations determines the stationary probabilities of the states. Many performance measures can be obtained directly from this stationary solution. Such unbounded nets can eliminate the state explosion problem of some models by using unbounded but simple approximations to bounded but complex model