A semi-quantitative approach to risk analysis, as an alternative to QRAs

In quantitative risk analysis (QRA) risk is quantified using probabilities and expected values, for example expressed by PLL values, FAR values, IR values and F–N curves. The calculations are tedious and include a strong element of arbitrariness. The value added by the quantification can certainly be questioned. In this paper, we argue that such analyses often are better replaced by semi-quantitative analyses, highlighting assessments of hazards and barriers, risk influencing factors (RIFs) and safety improvement measures. The assessments will be based on supporting information produced by risk analysts, including hard data and analyses of failure causes and mechanisms, barrier performance, scenario development, etc. The approach acknowledges that risk cannot be adequately described and evaluated simply by reference to summarising probabilities and expected values. There is a need for seeing beyond the standard probabilistic risk results of a QRA. Key aspects to include are related to uncertainties in phenomena and processes, and manageability factors. Such aspects are often ignored in standard QRAs.     

Risk informed decision-making and its ethical basis

In decision-making under uncertainty there are two main questions that need to be evaluated: (i) What are the future consequences and associated uncertainties of an action, and (ii) what is a good (or right) decision or action. Philosophically these issues are categorized as epistemic questions (i.e. questions of knowledge) and ethical questions (i.e. questions of moral and norms). This paper discusses the second issue, and evaluates different risk management approaches for establishing good decisions, using different ethical theories as a basis. These theories include the utilitarian ethics of Bentley and Mills, and deontological ethics of Kant, Rawls and Habermas. The risk management approaches include cost–benefit analysis (CBA), minimum safety criterion, the ALARP principle and the precautionary principle.     

A figure of merit for optimization of nanocrystal flash memory design

Nanocrystals can be used as storage media for carriers in flash memories. The performance of a nanocrystal flash memory depends critically on the choice of nanocrystal size and density as well as on the choice of tunnel dielectric properties. The performance of a nanocrystal memory device can be expressed in terms of write/erase speed, carrier retention time and cycling durability. We present a model that describes the charge/discharge dynamics of nanocrystal flash memories and calculate the effect of nanocrystal, gate, tunnel dielectric and substrate properties on device performance. The model assumes charge storage in quantized energy levels of nanocrystals. Effect of temperature is included implicitly in the model through perturbation of the substrate minority carrier concentration and Fermi level. Because a large number of variables affect these performance measures, in order to compare various designs, a figure of merit that measures the device performance in terms of design parameters is defined as a function of write/erase/discharge times which are calculated using the theoretical model. The effects of nanocrystal size and density, gate work function, substrate doping, control and tunnel dielectric properties and device geometry on the device performance are evaluated through the figure of merit. Experimental data showing agreement of the theoretical model with the measurement results are presented for devices that has PECVD grown germanium nanocrystals as the storage media.     

Characterisation of Diesel Engine Cylinder Liner Deposits by Surface Measurements

This paper briefly reviews cylinder liner deposits and describes their effect on lubricating oil consumption and surface topography. Cylinder liner deposits may be invisible to the naked eye, but can be identified by surface topography measurement. A simulation of a cylinder liner with deposits is used to identify which of the available surface characteristics is best suited as a measure of deposit severity. Surface measurements are used to detect deposits in a case study. The deposits are found to be concentrated in a belt around the mid-stroke region of the cylinder liner. The comparatively low position of the deposit may explain the slow response of a fuel additive treatment in restoring oil consumption control, as the additive treatment in this case is seen to be most effective in the uppermost part of the cylinder liner.     

Conservation of energy for schemes applied to the propagation of shallow‐water inertia‐gravity waves in regions with varying depth

The linear equations governing the propagation of inertia‐gravity waves in geophysical fluid flows are discretized on the Arakawa C‐grid using centered differences in space. In contrast to the constant depth case it is demonstrated that varying depth may give rise to increasing energy (and loss of stability) using the natural approximations for the Coriolis terms found in many well‐known codes. This is true no matter which numerical method is used to propagate the equations. By a simple trick based on a modified weighting that ensures that the propagation matrices for the spatially discretized equations become similar to skew‐symmetric matrices, this problem is removed and the energy is conserved in regions with varying depth too. We give a number of examples both of model problems and large‐scale problems in order to illustrate this behaviour. In real applications diffusion, explicit through frictional terms or implicit through numerical diffusion, is introduced both for physical reasons, but often also in order to stabilize the numerical experiments. The growing modes associated with varying depth, the C‐grid and equal weighting may force us to enhance the diffusion more than we would like from physical considerations. The modified weighting offers a simple solution to this problem. Copyright © 2000 John Wiley & Sons, Ltd.     

Profit loss indicator:a novel maintenance indicator applied for integrated planning

In production environment today,"silo thinking"is a challenge where controlling an asset associated with several disciplines and departments can lead to a suboptimal result.This requires a more integrated approach with an integrated planning(IPL)framework.In this framework novel maintenance key performance indicators(KPIs)are needed.The purpose of this article is to develop the novel maintenance KPI profit loss indicator(PLI).This indicator is based on measuring both on the"hidden factory"and waste in production,presenting it as a financial measure.The notion"hidden factory"is used as a metaphor for measuring the time losses in industry through the maintenance KPI overall equipment effectiveness(OEE).This indicator divides the time losses into availability losses,performance losses and quality losses.In addition,a financial measure for waste based on literature from Toyota production system(TPS)and waste treatment and disposal is also included in PLL Through a case study in the saw mill industry PLI is demonstrated and evaluated.It is expected that this indicator will be demonstrated in several industry branches in the future.     

GLEEBLE MACHINE DETERMINATION OF CREEP LAW PARAMETERS FOR THERMALLY INDUCED DEFORMATIONS IN ALUMINIUM DC CASTING

By means of a Gleeble machine, the flow stress at steady-state creep in an AA3103 aluminium alloy has been measured for temperatures and strain rates relevant for thermally induced deformations in DC casting. The strain rate has been determined by measuring the global radial strain rate at the specimen center by an extensometer, and the stress has been set equal to the force in the axial direction divided by the cross-section area. The parameters of Garofalo's equation have been fitted to the resulting steady-state stress and strain rate. Such a method is based upon the assumption of homogeneous stress and strain rate fields. In the Gleeble machine, the specimens are heated by the Joule effect leading to axial temperature gradients, and the specimen geometry is noncylindrical. The resulting inhomogeneities in the stress and strain rate fields are studied by finite element modeling, and it is shown that although they can be significant, the global radial strain rate and the axial force divided by the cross-section area at the specimen center can be relatively close to what the respective strain rate and stress values would have been if the conditions actually were homogeneous.     

CD40/APC-specific antibodies with three T-cell epitopes loaded in the constant domains induce CD4+ T-cell responses

CD4+ T lymphocytes play a central role in the orchestration and maintenance of the adaptive immune response. Targeting of antigen to antigen presenting cells (APCs) increases peptide loading of major histocompatibility complex (MHC) class II molecules and CD4+ T-cell activation. APCs have been targeted by APC-specific recombinant antibodies (rAbs) with single T-cell epitopes integrated in the constant region of the heavy chain (C(H)). However, the strategy may be improved if several T-cell epitopes could be delivered simultaneously by one rAb. We here demonstrate that a single rAb can be loaded with multiple identical or different T-cell epitopes, integrated as loops between β-strands in C(H) domains. One epitope was inserted in C(H)1, while two were placed in C(H)2 of IgG. T-cell proliferation assays showed that all three peptides were excised from loops and presented on MHC class II to T-cells. Induction of T-cell activation by each epitope in the multi-peptide rAb was as good, or even better, than that elicited by corresponding single-peptide rAbs. Furthermore, following DNA vaccination of mice with plasmids that encode CD40-specific rAbs loaded with either one or three peptides, T-cell responses were induced. Thus, integration of multiple epitopes in C(H) region loops of APC-specific rAbs is feasible and may be utilized in design of multi-vaccines.     

Optimal inspection when the system is repaired upon detection of failure

In Barlow and Proschan (Mathematical Theory of Reliability, 1965, Section 3.2) a cost model is presented for a system subject to random failure and whose state is known only by inspection. Upon detection of failure repair (or replacement) is performed and the system is then as good as new. A method of determining the inspection schedule which minimizes the long run average (expected) cost per unit time is proposed. In this present paper we look closer into the problem of finding an optimal inspection schedule for this model. Some new results, which are useful in connection with the computation of the optimal inspection schedule, are given.