Hierarchical models of very large problems, dilemmas, prospects, and an agenda for the future

Interdisciplinary approaches to the modeling of global problems are discussed in terms of multilevel cooperation. A multilevel regionalized model of the Lake Erie Basin is analyzed along with a multilevel regionalized world modeling project. Other topics discussed include: a stratified model of interacting region in a world system, and the application of the model to the world food crisis in south Asia. Recommended research for future development of integrated models is included

A Control Method for Static VAR Compensator Based On Modular Multilevel Inverter

Multilevel inverters are promised to provide a better performance in high power applications such as static VAR compensators. The proposed modular inverter has advantages compared to the conventional technologies. A control system of static VAR compensator using new modular multilevel inverter is proposed in this paper. Modeling and dynamic performance of static VAR compensator based on the proposed multilevel inverter are described in this paper. The inverter switching devices are switched at the fundamental output frequency. How to control the dc capacitor voltage is described. Several simulated results are included to verify the proposed concept. Keywords: Multilevel, inverter, STATCO

On-line Fault Diagnosis of Produced Water Treatment with Multilevel Flow Modeling

Making sense of alarms can be difficult on oil and gas platforms. Multilevel Flow Modeling provides a structure for modelling plant functionality and inferring causes for alarms and predicting consequences. Currently, Multilevel Flow Modeling has limited application for on-line fault diagnosis. Based on a fault emulated on a pilot plant for offshore produced water treatment, Multilevel Flow Modeling is used for reasoning about causes for triggered alarms. The inferred causes are analysed to investigate the current maturity of Multilevel Flow Modeling for on-line diagnosis.</p

Effort of Multilevel Modeling in Organizational Research : Citizenship Organizational Behavior and Work Performance on Task, with Spiritual Leadership Predictor, Work Spirituality Climate, and Open Organizational Culture

Considering the hierarchy style in real organization, some theorists have been interested in finding the best way to measuring variable in order to fit with the concept, and also analyzing hierarchy data syle such as data in individual, group, and organizational level. The aim of this writing is to make a start as pioneer in multilevel research in Indonesia, especially in citizenship organizational behavior. The script of this research is preparing the model of employee work performance (individual level) such as citizenship organizational behavior and work performance with job unit level like spiritual leadership, open organizational culture, and spritual work climate as predictors

Tensor polarizability and dispersive quantum measurement of multilevel atoms

Optimally extracting information from measurements performed on a physical system requires an accurate model of the measurement interaction. Continuously probing the collective spin of an Alkali atom cloud via its interaction with an off-resonant optical probe is an important example of such a measurement where realistic modeling at the quantum level is possible using standard techniques from atomic physics. Typically, however, tutorial descriptions of this technique have neglected the multilevel structure of realistic atoms for the sake of simplification. In this paper we account for the full multilevel structure of Alkali atoms and derive the irreducible form of the polarizability Hamiltonian describing a typical dispersive quantum measurement. For a specific set of parameters, we then show that semiclassical predictions of the theory are consistent with our experimental observations of polarization scattering by a polarized cloud of laser-cooled Cesium atoms. We also derive the signal-to-noise ratio under a single measurement trial and use this to predict the rate of spin-squeezing with multilevel Alkali atoms for arbitrary detuning of the probe beam.Comment: Significant corrections to theory and data. Full quality figures and other information available from http://minty.caltech.edu/papers.ph

Stochastic turbulence modeling in RANS simulations via Multilevel Monte Carlo

A multilevel Monte Carlo (MLMC) method for quantifying model-form uncertainties associated with the Reynolds-Averaged Navier-Stokes (RANS) simulations is presented. Two, high-dimensional, stochastic extensions of the RANS equations are considered to demonstrate the applicability of the MLMC method. The first approach is based on global perturbation of the baseline eddy viscosity field using a lognormal random field. A more general second extension is considered based on the work of [Xiao et al.(2017)], where the entire Reynolds Stress Tensor (RST) is perturbed while maintaining realizability. For two fundamental flows, we show that the MLMC method based on a hierarchy of meshes is asymptotically faster than plain Monte Carlo. Additionally, we demonstrate that for some flows an optimal multilevel estimator can be obtained for which the cost scales with the same order as a single CFD solve on the finest grid level.Comment: 40 page

Working Conditions, Absence and Gender - a Multilevel Study

In this paper we use data that combines employment records with employee survey responses to study to what extent psychosocial working conditions, measured at the work group level, relate to individual short-term and long-term sick leave. In order to take interdependencies of workers and work groups into consideration we use multilevel modeling as our modeling strategy. Our results suggest that in order to reduce the number of spells of short-term sick leave (shirking), employers should increase the worker’s job autonomy. This is particularly important for male workers. In addition, increasing work group cohesion is important in order to reduce the number of women being on long-term sick leave.Working conditions; absence; gender