| 1. |
- Kang, Byung-Soo, et al.
(author)
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Metal plasma immersion ion implantation and deposition (MePIIID) on screw-shaped titanium implant: The effects of ion source, ion dose and acceleration voltage on surface chemistry and morphology.
- 2011
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In: Medical Engineering & Physics. - : Elsevier BV. - 0951-8320 .- 1350-4533. ; 33:6, s. 730-738
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Journal article (peer-reviewed)abstract
- The present study investigated the effect of metal plasma immersion ion implantation and deposition (MePIIID) process parameters, i.e., plasma sources of magnesium and calcium, ion dose, and acceleration voltage on the surface chemistry and morphology of screw-type titanium implants that have been most widely used for osseointegrated implants. It is found that irrespective of plasma ion source, surface topography and roughness showed no differences at the nanometer level; that atom concentrations increased with ion dose but decreased with acceleration voltage. Data obtained from X-ray photoelectron spectroscopy and auger electron spectroscopy suggested that MePIIID process produces ‘intermixed’ layer of cathodic arc deposition and plasma immersion ion implantation. The MePIIID process may create desired bioactive surface chemistry of dental and orthopaedic implants by tailoring ion and plasma sources and thus enable investigations of the effect of the surface chemistry on bone response.
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| 2. |
- Bergman, Bo, et al.
(author)
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Letter to the editors
- 1988
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In: Reliability Engineering & System Safety. - : Elsevier BV. - 0951-8320 .- 1879-0836. ; 21:2, s. 155-160
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Journal article (other academic/artistic)
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| 3. |
- Hollnagel, Erik
(author)
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Looking for errors of omission and commission or The Hunting of the Snark revisited
- 2000
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In: Reliability Engineering & System Safety. - 0951-8320 .- 1879-0836. ; 68:2, s. 135-145
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Journal article (peer-reviewed)abstract
- Since the early 1990s, considerable effort has been spent to understand what is meant by an `error of commission' (EOC), to complement the traditional notion of an `error of omission' (EOO). This paper argues that the EOO-EOC dyad, as an artefact of the PSA event tree, is insufficient for human reliability analysis (HRA) for several reasons: (1) EOO-EOC fail to distinguish between manifestation and cause, (2) EOO-EOC refer to classes of incorrect actions rather than to specific instances: (3) there is no unique way of classifying an event using EOO-EOC, (4) the set of error modes that cannot reasonably be classified as EOO is too diverse to fit into any single category of its own. Since the use of EOO-EOC leads to serious problems for HRA. an alternative is required. This can be found in the concept of error modes, which has a long history in risk analysis. A specific system for error mode prediction was tested in a simulator experiment. The analysis of the results showed that error modes could be qualitatively predicted with sufficient accuracy (68% correct) to propose this method as a way to determine how operator actions can fail in PSA-cum-HRA. Although this still leaves the thorny issue of quantification, a consistent prediction of error modes provides a better starting point for determining probabilities than the EOO-EOC dyad. It also opens a possibility for quantification methods where the influence of the common performance conditions is prior to and more important than individual failure rates.
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| 4. |
- Hult, Peter, 1964-, et al.
(author)
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A bioacoustic method for timing of the different phases of the breathing cycle and monitoring of breathing frequency
- 2000
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In: Medical Engineering and Physics. - 1350-4533 .- 1873-4030. ; 22:6, s. 425-433
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Journal article (peer-reviewed)abstract
- It is well known that the flow of air through the trachea during respiration causes vibrations in the tissue near the trachea, which propagate to the surface of the body and can be picked up by a microphone placed on the throat over the trachea. Since the vibrations are a direct result of the airflow, accurate timing of inspiration and expiration is possible. This paper presents a signal analysis solution for automated monitoring of breathing and calculation of the breathing frequency. The signal analysis approach uses tracheal sound variables in the time and frequency domains, as well as the characteristics of the disturbances that can be used to discriminate tracheal sound from noise. One problem associated with the bioacoustic method is its sensitivity for acoustic disturbances, because the microphone tends to pick up all vibrations, independent of their origin. A signal processing method was developed that makes the bioacoustic method clinically useful in a broad variety of situations, for example in intensive care and during certain heart examinations, where information about both the precise timing and the phases of breathing is crucial.
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| 5. |
- Kumar, Dhananjay, et al.
(author)
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Proportional hazards model : a review
- 1994
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In: Reliability Engineering & System Safety. - : Elsevier BV. - 0951-8320 .- 1879-0836. ; 44:2, s. 177-188
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Journal article (peer-reviewed)abstract
- The proportional hazards model was introduced in 1972 by D. R. Cox in order to estimate the effects of different covariates influencing the times to the failures of a system. The model has been used rather extensively in biomedicine and, recently, interest in its application in reliability engineering has increased. The main purpose of this expository paper is to review the existing literature on the proportional hazards model. At first, the characteristics of the method are explained and its importance in reliability analysis is presented. Subsequently, methods for estimating parameters, along with the small and large sample properties of the estimators, are briefly discussed. Afterwards, work carried out so far on topics such as the effects of interaction, omission, measurement error, misclassification, monotonicity, multicolinearity and time dependency of covariates on the estimator are summarized. Some goodness-of-fit tests, especially those based on graphical methods, are described. We also describe some possible extensions of this model considered so far and available computer programs and packages for estimating the parameters of this model. Finally, some areas for further research are also discussed. (100 refs.)
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| 6. |
- Kumar, Dhananjay, et al.
(author)
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Reliability analysis of power transmission cables of electric mine loaders using the proportional hazards model
- 1992
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In: Reliability Engineering & System Safety. - : Elsevier BV. - 0951-8320 .- 1879-0836. ; 37:3, s. 217-222
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Journal article (peer-reviewed)abstract
- The proportional hazards model (PHM) is a powerful technique which can be used to investigate the effects of operating environment and the diagnostic variables (covariates) associated with an item on its life length. The effects of two different designs and maintenance on the reliability of a power transmission cable of an electric mine loader is investigated using PHM. The purpose is to illustrate the application of this model in making decisions about selecting the proper material or designing an item to meet the required purpose efficiently. (11 refs.)
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| 7. |
- Kumar, Uday, et al.
(author)
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Reliability analysis of hydraulic systems of LHD machines using the power law process model
- 1992
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In: Reliability Engineering & System Safety. - : Elsevier BV. - 0951-8320 .- 1879-0836. ; 35:3, s. 217-224
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Journal article (peer-reviewed)abstract
- Previously, a preliminary study of the reliability characteristics of a fleet of load-haul-dump (LHD) machines deployed at Kiruna mine showed that the engine and the hydraulics are the two most critical subsystems. Hydraulic systems are selected for further study because such systems are still under a development phase. Maintenance data for two years for these machines are analyzed. The tests for trends and serial correlation show that times between successive failures for the hydraulic systems are in most cases not independent and identically distributed. Goodness-of-fit tests show that the power law process model provides a good fit to the failure data of the hydraulic systems. Methods for parameter estimation in the power law process model and estimation of optimal maintenance intervals for such systems are presented. Emphasis is on the use of graphical methods for data analysis (14 refs.)
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| 8. |
- Kumar, Uday, et al.
(author)
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Reliability investigation for a fleet of load haul dump machines in a Swedish mine
- 1989
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In: Reliability Engineering & System Safety. - : Elsevier BV. - 0951-8320 .- 1879-0836. ; 26:4, s. 341-361
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Journal article (peer-reviewed)abstract
- The recent trends of deployment of complex and capital intensive equipment in mines has created interest in the field of maintenance and operational reliability of this equipment. The failure consequences associated with random equipment failures have considerable influence on the total operating cost of a highly mechanized mining system. Keeping this in view, a reliability investigation was initiated for a fleet of diesel operated load-haul-dump (LHD) machines in a Swedish mine. The goal is to estimate the operational reliability of these machines, locate items or assemblies which need improvement in design to enhance the reliability and to decide the duration of optimal preventive maintenance. Failure data for one year of LHD machines are analysed using the recently developed graphical technique of total time on test (TTT) plotting. Analytical methods like Kolmogorov-Smirnov test and maximum likelihood estimation are used in the analysis. The importance of testing the reliability data for the presence of trends and serial correlation is also emphasized.
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| 9. |
- Sjöberg, Lennart
(author)
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Author's reply: Whose risk perception should influence decisions?
- 2001
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In: Reliability Engineering & System Safety. - : Elsevier Ltd. - 1879-0836 .- 0951-8320. ; 72:2, s. 149-151
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Journal article (other academic/artistic)abstract
- My paper is being commented upon in three interesting papers [1], [2], [3]. I will deal with them in turn since they are quite different and will finish with a discussion of a common theme.
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| 10. |
- Sjöberg, Lennart
(author)
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Political decisions and public risk perception
- 2001
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In: Reliability Engineering & System Safety. - : Elsevier Ltd. - 1879-0836 .- 0951-8320. ; 72:2, s. 115-123
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Journal article (peer-reviewed)abstract
- Should the public's risk perception be an input into political and administrative decision making? It is clear that it does have an influence, but perhaps not to the extent of explaining all, or even most, of the tremendous inconsistencies in the allocation of resources for risk mitigation. Risk perception models could be of help to understand such phenomena, but contemporary models of risk perception have been misleading and their weaknesses are discussed. Similarly, experts' risk perception has been asserted to be very different from that of the public but that is argued here to be a mistaken opinion. Should we let the experts run risk policy? Several arguments against this idea are put forward here, the most important being that the whole issue is one of democracy. Those who are unhappy about the decisions made by the government can always argue their case and maybe gain political power to change things. This is as true of risk policy as it is of everything else.
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