Number Of Identical Elements Research Articles

Odd thermodynamic limit for the Loschmidt echo

Is it possible to readily distinguish a system made by an Avogadro's number of identical elements and one with a single additional one? Usually, the answer to this question is negative but, in this work, we show that in antiferromagnetic quantum spin rings a simple out-of-equilibrium experiment can do so, yielding two qualitatively and quantitatively different outcomes depending on whether the system includes an even or an odd number of elements. We consider a local quantum-quench setup and calculate a generating function of the work done, namely, the Loschmidt echo, showing that it displays different features depending on the presence or absence of topological frustration, which is triggered by the even/oddness in the number of the chain sites. We employ the prototypical quantum Ising chain to illustrate this phenomenology, which we argue being generic for antiferromagnetic spin chains, as it stems primarily from the different low energy spectra of frustrated and non frustrated chains. Our results thus prove that these well-known spectral differences lead indeed to distinct observable characteristics and open the way to harvest them in quantum thermodynamics protocols.

MATHEMATICAL MODELS OF RELIABILITY OF POWER SUPPLY SYSTEMS

Ensuring reliability is one of the most important issues in the creation and operation of any technical system. This is especially important for complex systems, such as power supply systems with internal and external connections consisting of many elements. The task of ensuring the reliability of power supply systems includes a whole set of technical, economic and organizational measures aimed at reducing damage caused by violations of the normal mode of operation of electricity consumers. To obtain information about the reliability of elements of power supply systems, it is necessary to study a fairly large number of identical elements over a long period of time. In the real conditions of an industrial enterprise, this creates certain difficulties, so it is possible to conduct an accelerated reliability test using mathematical modeling [3].
 The article discusses some ways to solve the main problem of reliability theory - building a mathematical model and obtaining criteria for selecting optimal options for power supply systems. In this paper, the main materials for calculating the reliability of power supply systems using the mathematical apparatus of probability theory are presented.

Learning better by repetition or variation? Is transfer at odds with task specific training?

ObjectiveTransfer of motor skills is the ultimate goal of motor training in rehabilitation practice. In children with Developmental Coordination Disorder (DCD), very little is known about how skills are transferred from training situations to real life contexts. In this study we examined the influence of two types of practice on transfer of motor skills acquired in a virtual reality (VR) environment.MethodOne hundred and eleven children with DCD and their typically developing (TD) peers, aged 6–10 years (M = 8.0 SD = 1.0) were randomly assigned to either variable (n = 56) or repetitive practice (n = 55). Participants in the repetitive practice played the same exergame (ski slalom) twice weekly for 20 minutes, over a period of 5 weeks, while those in the variable group played 10 different games. Motor skills such as balance tasks (hopping), running and agility tasks, ball skills and functional activities were evaluated before and after 5 weeks of training.ResultsANOVA repeated measures indicated that both DCD and TD children demonstrated transfer effects to real life skills with identical and non-identical elements at exactly the same rate, irrespective of the type of practice they were assigned to.ConclusionBased on these findings, we conclude that motor skills acquired in the VR environment, transfers to real world contexts in similar proportions for both TD and DCD children. The type of practice adopted does not seem to influence children’s ability to transfer skills acquired in an exergame to life situations but the number of identical elements does.

Computer numerical control vertical machining centre feed drive modelling using the transmission line technique

This study presents a novel application of the Transmission Line Matrix Method (TLM) for the modelling of the dynamic behaviour of non-linear hybrid systems for computer numerical control (CNC) machine tool drives. The application of the TLM technique implies the dividing of the ball-screw shaft into a number of identical elements in order to achieve the synchronisation of events in the simulation, and to provide an acceptable resolution according to the maximum frequency of interest. This entails the use of a high performance computing system with due consideration to the small time steps being applied in the simulation. Generally, the analysis of torsion and axial dynamic effects on a shaft implies the development of independent simulated models. This study presents a new procedure for the modelling of a ball-screw shaft by the synchronisation of the axial and torsion dynamics into the same model. The model parameters were obtained with equipments such as laser interferometer, ball bar, electronic levels, signal acquisition systems, etc. The MTLM models for single and two-axis configurations have been simulated and matches well with the measured responses of machines. The new modelling approach designated the Modified Transmission Line Method (MTLM) extends the TLM approach retaining all its inherent qualities but gives improved convergence and processing speeds. Further work since, not the subject of this paper, have identified its potential for real-time application.

Resonance features of the allowed and forbidden bands of the microwave photonic crystal with periodicity defects

The resonance features of the allowed and forbidden bands of the microwave waveguide photonic crystals with periodicity defects are theoretically and experimentally analyzed. It is demonstrated that the number of resonances in the allowed band is determined by the number of identical elements whose periodic sequence determines the photonic crystal and the maximum Q factor is reached in the vicinity of the lower and upper boundaries of the allowed band. An increase in the size of the forbidden bands and a decrease in the size of the allowed bands of the microwave photonic crystal due to a decrease in the number of resonances in the allowed band are caused by violations of periodicity of the photonic crystal related to nonidentity of a single element.

Standardization and optimum structural design by dynamic programming

The paper is concerned with tools for optimum structural design that can taken into account the industrial production of structural elements. Standardization is considered here as the result of minimizing the cost as a function of both element sizes and numbers of identical elements. The optimum value of the design variables obtained by traditional minimum weight (volume) design is taken as the starting point for the present procedure. Dynamic programming is used for standardization decisions. The method seems to be particularly effective when the cost function for each element size can be regarded as the sum of a constant term (initial investment) and a term that is proportional to the number of identical elements (cost of production).

Inductively coupled bit memories

The application of inductively coupled magnetic films to memory organization is described. Experimental work resulted in bilateral flux transfer between magnetic film elements of equal size. The influence of the device and coupling loop parameters, as well as the rise time of the drive pulse, on the maximum number of identical elements for a generalized model is shown. The parts used experimentally to demonstrate bilateral flux transfer were chain-store elements electrolessly plated with 20 000 A of nickel-iron film. Continual flux transfer back and forth on a tight flat coupling loop was obtained. Structures required to effectively use inductively coupled magnetic films in memory organizations were investigated. Application of inductively coupled magnetic films implies the possibilities of large memories, nondestructive readout memories, or 3D-like organization for magnetic film device memories.