181,793 research outputs found
Some Remarks on the Use of Deterministic and Probabilistic Approaches in the Evaluation of Rock Slope Stability
The rock slope stability assessment can be performed by means of deterministic and
probabilistic approaches. As the deterministic analysis needs only representative values (generally,
the mean value) for each physical and geo-mechanical parameter involved, it does not take into
account the variability and uncertainty of geo-structural and geo-mechanical properties of joints. This
analysis can be usually carried out using dierent methods, such as the Limit Equilibrium method or
numerical modeling techniques sometimes implemented in graphical tests to identify dierent failure
mechanisms (kinematic approach). Probabilistic methods (kinetic approach) aimed to calculate the
slope failure probability, consider all orientations, physical characters and shear strength of joints
and not only those recognized as kinematically possible. Consequently, the failure probability can
be overestimated. It is, therefore, considered more realistic to perform both kinematic and kinetic
analyses and to calculate a conditional probability given by the product of the kinematic and kinetic
probabilities assuming that they are statistically independent variables. These approaches have been
tested on two rock slopes in the Campanian region of Southern Italy aected by possible plane and
wedge failures, respectively. Kinematic and kinetic probabilities have been evaluated both by means
of the Markland’s test and the Monte Carlo simulation. Using the Eurocode 7, also a deterministic
limit equilibrium analysis was performed. The obtained results were compared and commented on
Biomechanical Evaluation of the Accuracy in Radiographic Assessment of Femoral Component Migration Measurement after Total Hip Arthroplasty
Introduction: Implant subsidence is one criteria utilized to monitor for prosthesis loosening after total hip arthroplasty (THA) with initial implant subsidence assessment often done utilizing plain radiographs. The specific aim of this study was to identify the most reliable references when using plain radiographs to establish an image magnification with the goals being easy to use, inexpensive, reliable, and accurate.
Methods: Two femoral stem implants (stem lengths: 127mm, 207mm) were utilized to simulate hemiarthroplasty of the hip with composite femurs. Different combinations of femoral stem distances from the radiographic film (ODD), source-detector differences (SDD), hip rotation, and hip flexion were elected. Standardized anterior-posterior pelvis for each parameter combination setup were taken. Radiographic measurements (head diameter, stem length, stem seating length) were undertaken five times by three examiners. Radiographic image magnification factors were generated from two references (head diameter and stem length). Radiograph measurement reproducibility and stem seating length errors using these magnification factors were evaluated.
Results: High level of repeated measurements reliability was found for head diameter (99 ± 0%) and stem length (90 ± 7%) measurements, whereas seating length measurements were less reliable (76 ± 6%). Stem length error using the femoral head magnification factor yielded 11% accuracy. Stem seating length error using both magnification factors were not reliable (< 7% accuracy). All parameters, except SDD, showed significant effect on calibrated measurement error.
Conclusions: Current methods of assessing implant subsidence after THA using plain radiographs are inaccurate or reliable. Clinicians should recognize these limitations and be cautious when diagnosing implant stability using plain radiographs alone
Expert Elicitation for Reliable System Design
This paper reviews the role of expert judgement to support reliability
assessments within the systems engineering design process. Generic design
processes are described to give the context and a discussion is given about the
nature of the reliability assessments required in the different systems
engineering phases. It is argued that, as far as meeting reliability
requirements is concerned, the whole design process is more akin to a
statistical control process than to a straightforward statistical problem of
assessing an unknown distribution. This leads to features of the expert
judgement problem in the design context which are substantially different from
those seen, for example, in risk assessment. In particular, the role of experts
in problem structuring and in developing failure mitigation options is much
more prominent, and there is a need to take into account the reliability
potential for future mitigation measures downstream in the system life cycle.
An overview is given of the stakeholders typically involved in large scale
systems engineering design projects, and this is used to argue the need for
methods that expose potential judgemental biases in order to generate analyses
that can be said to provide rational consensus about uncertainties. Finally, a
number of key points are developed with the aim of moving toward a framework
that provides a holistic method for tracking reliability assessment through the
design process.Comment: This paper commented in: [arXiv:0708.0285], [arXiv:0708.0287],
[arXiv:0708.0288]. Rejoinder in [arXiv:0708.0293]. Published at
http://dx.doi.org/10.1214/088342306000000510 in the Statistical Science
(http://www.imstat.org/sts/) by the Institute of Mathematical Statistics
(http://www.imstat.org
Managing Well Integrity using Reliability Based Models
Imperial Users onl
Blood glucose monitoring in children and adolescents with Type 1 Diabetes Mellitus
Aim: The aims of this review are to explore and quantify the importance of blood glucose monitoring on glycaemic control in children and adolescents with Type 1 Diabetes Mellitus (T1DM). Methods: A literature search of the major bibliographic databases found 11 observational studies which met the inclusion criteria of this review. Results: 9 of the 11 papers found a significant link between self-monitoring of blood glucose (SMBG) frequency and HbA1c reduction, with SMBG monitoring 4 times daily leading to a further reduction in HbA1c of 1% compared to once daily monitoring. Frequent SMBG was correlated to higher social status, higher self-efficacy and increased parental involvement and was a sign of better global self-care behaviour. It was also noted that frequent SMBG leads to improved glycaemic control only if patients are taught what to do with the results and if they have an insulin regimen that allows for adjustment of insulin doses in response to blood glucose values. Conclusion: Frequent SMBG monitoring is an important part of diabetes self-management in children and adolescents with T1DM because it results in a significant reduction in HbA1c. In the long-term this will lead to a reduction in the late complications of T1DM. Providing children and adolescents with T1DM in Malta with an adequate supply of glucose test strips should serve as an incentive for them to check their blood glucose regularly.peer-reviewe
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