A new approach to analysing human-related accidents by combined use of HFACS and activity theory-based method

This study proposes a new method for modelling and analysing human-related accidents. It integrates HFACS (Human Factors Analysis and Classification System), which addresses most of the socio-technical system levels and offers a comprehensive failure taxonomy for analysing human errors, and AT (Activity Theory)-based approach, which provides an effective way for considering various contextual factors systematically in accident investigation. By combining them, the proposed method makes it more efficient to use the concepts and principles of AT. Additionally, it can help analysts use HFACS taxonomy more coherently to identify meaningful causal factors with a sound theoretical basis of human activities. Therefore, the proposed method can be effectively used to mitigate the limitations of traditional approaches to accident analysis, such as over-relying on a causality model and sticking to a root-cause, by making analysts look at an accident from a range of perspectives. To demonstrate the usefulness of the proposed method, we conducted a case study in nuclear power plants. Through the case study, we could confirm that it would be a useful method for modelling and analysing human-related accidents, enabling analysts to identify a plausible set of causal factors efficiently in a methodical consideration of contextual backgrounds surrounding human activities

Understanding the effect resonant magnetic perturbations have on ELMs

All current estimations of the energy released by type I ELMs indicate that, in order to ensure an adequate lifetime of the divertor targets on ITER, a mechanism is required to decrease the amount of energy released by an ELM, or to eliminate ELMs altogether. One such amelioration mechanism relies on perturbing the magnetic field in the edge plasma region, either leading to more frequent, smaller ELMs (ELM mitigation) or ELM suppression. This technique of Resonant Magnetic Perturbations (RMPs) has been employed to suppress type I ELMs at high collisionality/density on DIII-D, ASDEX Upgrade, KSTAR and JET and at low collisionality on DIII-D. At ITER-like collisionality the RMPs enhance the transport of particles or energy and keep the edge pressure gradient below the 2D linear ideal MHD critical value that would trigger an ELM, whereas at high collisionality/density the type I ELMs are replaced by small type II ELMs. Although ELM suppression only occurs within limitied operational ranges, ELM mitigation is much more easily achieved. The exact parameters that determine the onset of ELM suppression are unknown but in all cases the magnetic perturbations produce 3D distortions to the plasma and enhanced particle transport. The incorporation of these 3D effects in codes will be essential in order to make quantitative predictions for future devices.Comment: 32 pages, 9 figure

The CP properties of the lightest Higgs boson with sbottom effects

In the framework of the recently proposed gluino-axion model, using the effective potential method and taking into account the top-stop as well as the bottom-sbottom effects, we discuss the CP--properties of the lightest Higgs boson, in particular its CP--odd composition, which can offer new opportunities at collider searches. It is found that although the CP-odd composition of the lightest Higgs increases slightly with the inclusion of the sbottom effects, it never exceeds %0.17 for all values of the renormalization scale Q ranging from top mass to TeV scaleComment: 24 pp, 12 eps fig

Orbital liquid in three dimensional Mott insulator: LaTiO3LaTiO_3

We present a theory of spin and orbital states in Mott insulator $LaTiO_3$. The spin-orbital superexchange interaction between $d^1(t_{2g})$ ions in cubic crystal suffers from a pathological degeneracy of orbital states at classical level. Quantum effects remove this degeneracy and result in the formation of the coherent ground state, in which the orbital moment of $t_{2g}$ level is fully quenched. We find a finite gap for orbital excitations. Such a disordered state of local degrees of freedom on unfrustrated, simple cubic lattice is highly unusual. Orbital liquid state naturally explains observed anomalies of $LaTiO_3$.Comment: 5 pages, 3 figure

Electroweak phase transition in a nonminimal supersymmetric model

The Higgs potential of the minimal nonminimal supersymmetric standard model (MNMSSM) is investigated within the context of electroweak phase transition. We investigate the allowed parameter space yielding correct electroweak phase transitoin employing a high temperature approximation. We devote to phenomenological consequences for the Higgs sector of the MNMSSM for electron-positron colliders. It is observed that a future $e^+ e^-$ linear collider with $\sqrt{s} = 1000$ GeV will be able to test the model with regard to electroweak baryogenesis.Comment: 28 pages, 5 tables, 12 figure