Goal-oriented adaptive sampling under random field modelling of response probability distributions

In the study of natural and artificial complex systems, responses that are not completely determined by the considered decision variables are commonly modelled probabilistically, resulting in response distributions varying across decision space. We consider cases where the spatial variation of these response distributions does not only concern their mean and/or variance but also other features including for instance shape or uni-modality versus multi-modality. Our contributions build upon a non-parametric Bayesian approach to modelling the thereby induced fields of probability distributions, and in particular to a spatial extension of the logistic Gaussian model. The considered models deliver probabilistic predictions of response distributions at candidate points, allowing for instance to perform (approximate) posterior simulations of probability density functions, to jointly predict multiple moments and other functionals of target distributions, as well as to quantify the impact of collecting new samples on the state of knowledge of the distribution field of interest. In particular, we introduce adaptive sampling strategies leveraging the potential of the considered random distribution field models to guide system evaluations in a goal-oriented way, with a view towards parsimoniously addressing calibration and related problems from non-linear (stochastic) inversion and global optimisation.

Development of improved performance electromagnetic valve for liquid rocket engine

The problem of developing optimal-design electromagnetic valves is relevant for many industries. The development of technology is characterized by increased power and pressures used for actuator mechanisms, as well as by reducing the dimensions and mass of automatic units. The goal of this article is to develop an advanced electromagnetic valve that would ensure optimal combination of high performance, reliability, technological effectiveness and minimal cost. On the basis of standard dependences for electromagnetic phenomena a mathematic model of a SU.1 valve was developed. It was calculated in several special-purpose software packages: NISA, FEMM, ANSYS Maxwell. Parametric analysis was implemented in ANSYS Maxwell for variable working gap settings and values of current force in the solenoid. As a result, the magnetic induction distribution field was obtained. The results of modeling the operation of the electromagnetic valve and the magnetic induction distribution field are presented for variable working gap settings and different values of current force in the solenoid. The model of an advanced electromagnetic valve for a liquid rocket engine was developed on the basis of the dependences obtained. The duration of single engine firing obtained is 40 msec. The results obtained make it possible to create a valve with hold-open time of 800msec, which is considered sufficient for application in electromagnetic direct current valves.

A Unified Theory of Neutral Grounding Methods in Power Distribution Systems

<p>The neutral grounding in power distribution system is an important aspect for earth fault protection, power supply reliability and safety. The performance varies greatly with different grounding methods by which the protective effect presents various results with identical impedance of single phase earth fault. Arguments for better neutral protection has been continued in the distribution field for decades, unfortunately, there is still not a conclusion due to the discussions lacking of a unified modelling or theory of neutral groundings. Thus, the understanding of neutral grounding in most countries differs considerably. Surprisingly solid/isolated grounding in some countries is still considered as a mainstream grounding method in today’s distribution grids, likewise, some utilities are still persisting on adopting resistance grounding to pursue to improve detection sensitivity and reliability, and so on. In this paper, a unified theory is proposed to shed light on the neutral groundings within one unprecedented modelling by which neutral groundings can be compared and evaluated quantitatively for the first time in the history of power distribution field perhaps.</p>

A Unified Theory of Neutral Grounding Methods in Power Distribution Systems

<p>The neutral grounding in power distribution system is an important aspect for earth fault protection, power supply reliability and safety. The performance varies greatly with different grounding methods by which the protective effect presents various results with identical impedance of single phase earth fault. Arguments for better neutral protection has been continued in the distribution field for decades, unfortunately, there is still not a conclusion due to the discussions lacking of a unified modelling or theory of neutral groundings. Thus, the understanding of neutral grounding in most countries differs considerably. Surprisingly solid/isolated grounding in some countries is still considered as a mainstream grounding method in today’s distribution grids, likewise, some utilities are still persisting on adopting resistance grounding to pursue to improve detection sensitivity and reliability, and so on. In this paper, a unified theory is proposed to shed light on the neutral groundings within one unprecedented modelling by which neutral groundings can be compared and evaluated quantitatively for the first time in the history of power distribution field perhaps.</p>

A Unified Theory of Neutral Grounding Methods in Power Distribution Systems

The neutral grounding in power distribution system is an important aspect for earth fault protection, power supply reliability and safety. The performance varies greatly with different grounding methods by which the protective effect presents various results with identical impedance of single phase earth fault. Arguments for better neutral protection has been continued in the distribution field for decades, unfortunately, there is still not a conclusion due to the discussions lacking of a unified modelling or theory of neutral groundings. Thus, the understanding of neutral grounding in most countries differs considerably. Surprisingly solid/isolated grounding in some countries is still considered as a mainstream grounding method in today’s distribution grids, likewise, some utilities are still persisting on adopting resistance grounding to pursue to improve detection sensitivity and reliability, and so on. In this paper, a unified theory is proposed to shed light on the neutral groundings within one unprecedented modelling by which neutral groundings can be compared and evaluated quantitatively for the first time in the history of power distribution field perhaps.

Mathematical Modelling of Material Flow during Friction Stir Welding of Aluminium Alloys

The paper presents the results of a mathematical model of the material flow during Friction Stir Welding (FSW) of aluminium alloys using a Finite Element Analysis. The authors presented their work on a two-dimensional visco-plastic model, using User Define Functions (UDF) in a commercial CFD code (FLUENT). The model developed was validated by microstructural investigations on experimental FSW joints and by a comparative analysis of temperature distribution field of the experimental FSW joint and numerical simulated model. The results confirmed that the mathematical model describes with a good precision the material flow and temperature field during FSW process.