Safety illusion and error trap in a collectively-operated machine accident

Workplace accidents involving machines are relevant for their magnitude and their impacts on worker health. Despite consolidated critical statements, explanation centered on errors of operators remains predominant with industry professionals, hampering preventive measures and the improvement of production-system reliability. Several initiatives were adopted by enforcement agencies in partnership with universities to stimulate production and diffusion of analysis methodologies with a systemic approach. Starting from one accident case that occurred with a worker who operated a brake-clutch type mechanical press, the article explores cognitive aspects and the existence of traps in the operation of this machine. It deals with a large-sized press that, despite being endowed with a light curtain in areas of access to the pressing zone, did not meet legal requirements. The safety devices gave rise to an illusion of safety, permitting activation of the machine when a worker was still found within the operational zone. Preventive interventions must stimulate the tailoring of systems to the characteristics of workers, minimizing the creation of traps and encouraging safety policies and practices that replace judgments of behaviors that participate in accidents by analyses of reasons that lead workers to act in that manner.

Efficient Placement of Fault Indicators in an Actual Distribution System Using Evolutionary Computing

This paper proposes an evolutionary computing strategy to solve the problem of fault indicator (FI) placement in primary distribution feeders. More specifically, a genetic algorithm (GA) is employed to search for an efficient configuration of FIs, located at the best positions on the main feeder of a real-life distribution system. Thus, the problem is modeled as one of optimization, aimed at improving the distribution reliability indices, while, at the same time, finding the least expensive solution. Based on actual data, the results confirm the efficiency of the GA approach to the FI placement problem.

Evaluation of quality of life in severely obese patients after bariatric surgery carried out in the public healthcare system

Objectives: To assess QoL of obese patients in the Brazilian public healthcare system, before and after bariatric surgery, and to determine the appropriateness of the Moorehead-Ardelt Questionnaire II (M-A-QoLQII) compared with the Short-Form Health Survey (SF-36). Subjects and methods: Forty-one severe obese patients in a waiting-list, and 84 patients who underwent bariatric surgery were included. Correlations were tested and reliability determined by the Cronbach's coefficient. Results: BMI differed between the pre- and post-surgery groups (52.3 +/- 8.3 kg/m(2) vs. 32.5 +/- 6.4 kg/m(2), p < 0.001). The latter showed better scores in the SF-36 domains than in the pre-surgery. SF-36 and M-A-QoLQII categories were correlated (r = 0.53, 0.49 and 0.47, for vitality, mental health, and general health domains, p < 0.001). In the logistic regression, age, previous BMI, and loss of excess weight were associated with functional capacity. Conclusions:The outcomes of bariatric surgery obtained in a Brazilian public healthcare center were successful. M-A-QoLII represents a useful tool to assess surgery outcomes, including QoL. Arq Bras Endocrinol Metab. 2012;56(1):33-8

Glucose Control in Acute Myocardial Infarction: A Pilot Randomized Study Controlled by Continuous Glucose Monitoring System Comparing the Use of Insulin Glargine with Standard of Care

Background: This pilot study aimed to verify if glycemic control can be achieved in type 2 diabetes patients after acute myocardial infarction (AMI), using insulin glargine (iGlar) associated with regular insulin (iReg), compared with the standard intensive care unit protocol, which uses continuous insulin intravenous delivery followed by NPH insulin and iReg (St. Care). Patients and Methods: Patients (n = 20) within 24 h of AMI were randomized to iGlar or St. Care. Therapy was guided exclusively by capillary blood glucose (CBG), but glucometric parameters were also analyzed by blinded continuous glucose monitoring system (CGMS). Results: Mean glycemia was 141 +/- 39 mg/dL for St. Care and 132 +/- 42 mg/dL for iGlar by CBG or 138 +/- 35 mg/dL for St. Care and 129 +/- 34 mg/dL for iGlar by CGMS. Percentage of time in range (80-180 mg/dL) by CGMS was 73 +/- 18% for iGlar and 77 +/- 11% for St. Care. No severe hypoglycemia (<= 40 mg/dL) was detected by CBG, but CGMS indicated 11 (St. Care) and seven (iGlar) excursions in four subjects from each group, mostly in sulfonylurea users (six of eight patients). Conclusions: This pilot study suggests that equivalent glycemic control without increase in severe hyperglycemia may be achieved using iGlar with background iReg. Data outputs were controlled by both CBG and CGMS measurements in a real-life setting to ensure reliability. Based on CGMS measurements, there were significant numbers of glycemic excursions outside of the target range. However, this was not detected by CBG. In addition, the data indicate that previous use of sulfonylurea may be a potential major risk factor for severe hypoglycemia irrespective of the type of insulin treatment.

A comparison of deterministic, reliability-based and risk-based structural optimization under uncertainty

In this paper, the effects of uncertainty and expected costs of failure on optimum structural design are investigated, by comparing three distinct formulations of structural optimization problems. Deterministic Design Optimization (DDO) allows one the find the shape or configuration of a structure that is optimum in terms of mechanics, but the formulation grossly neglects parameter uncertainty and its effects on structural safety. Reliability-based Design Optimization (RBDO) has emerged as an alternative to properly model the safety-under-uncertainty part of the problem. With RBDO, one can ensure that a minimum (and measurable) level of safety is achieved by the optimum structure. However, results are dependent on the failure probabilities used as constraints in the analysis. Risk optimization (RO) increases the scope of the problem by addressing the compromising goals of economy and safety. This is accomplished by quantifying the monetary consequences of failure, as well as the costs associated with construction, operation and maintenance. RO yields the optimum topology and the optimum point of balance between economy and safety. Results are compared for some example problems. The broader RO solution is found first, and optimum results are used as constraints in DDO and RBDO. Results show that even when optimum safety coefficients are used as constraints in DDO, the formulation leads to configurations which respect these design constraints, reduce manufacturing costs but increase total expected costs (including expected costs of failure). When (optimum) system failure probability is used as a constraint in RBDO, this solution also reduces manufacturing costs but by increasing total expected costs. This happens when the costs associated with different failure modes are distinct. Hence, a general equivalence between the formulations cannot be established. Optimum structural design considering expected costs of failure cannot be controlled solely by safety factors nor by failure probability constraints, but will depend on actual structural configuration. (c) 2011 Elsevier Ltd. All rights reserved.

Fatigue Reliability of 3 Single-Unit Implant-Abutment Designs

Objectives: Because the mechanical behavior of the implant-abutment system is critical for the longevity of implant-supported reconstructions, this study evaluated the fatigue reliability of different implant-abutment systems used as single-unit crowns and their failure modes. Methods and Materials: Sixty-three Ti-6Al-4V implants were divided in 3 groups: Replace Select (RS); IC-IMP Osseotite; and Unitite were restored with their respective abutments. Anatomically correct central incisor metal crowns were cemented and subjected to separate single load to failure tests and step-stress accelerated life testing (n = 18). A master Weibull curve and reliability for a mission of 50,000 cycles at 200 N were calculated. Polarized-light and scanning electron microscopes were used for failure analyses. Results: The load at failure mean values during step-stress accelerated life testing were 348.14 N for RS, 324.07 N for Osseotite, and 321.29 N for the Unitite systems. No differences in reliability levels were detected between systems, and only the RS system mechanical failures were shown to be accelerated by damage accumulation. Failure modes differed between systems. Conclusions: The 3 evaluated systems did not present significantly different reliability; however, failure modes were different. (Implant Dent 2012;21:67-71)

An epidemiological scoring system for tooth wear and dental erosive wear

Background: The prevalence and severity of tooth wear and dental erosion is rising in children and there is no consensus about an index to be employed. Aim: To assess the reliability of an epidemiological scoring system dental wear index (DWI) to measure tooth wear and dental erosive wear. Design: An epidemiological cross-sectional survey was conducted to evaluate and compare tooth wear and dental erosion using the dental wear index and erosion wear index (EWI). The study was conducted with randomised samples of 2,371 children aged between 4 years and 12 years selected from the State of São Paulo, Brazil. Records were used for calculating tooth wear and dental erosion; the incisal edge and canine cusp were excluded. Results: As the schoolchildren's ages increased the severity of primary tooth wear increased in canines (P = 0.0001, OR = 0.34) and molars (P = 0.0001, OR = 2.47) and erosion wear increased in incisal/occlusal (P = 0.0001, OR = 5.18) and molars (P = 0.0001, OR = 2.47). There was an increased prevalence of wear in the permanent teeth of older schoolchildren, particularly on the incisal/occlusal surfaces (P = 0.0001, OR = 7.03). Conclusion: The prevalence of tooth wear and dental erosion increased as age increased in children. The epidemiological scoring system Dental Wear Index is able to measure both tooth wear and dental erosive wear. This index should be used to monitor the progression of non-carious lesions and to evaluate the levels of disease in the population.

Laboratorial training of examiners for using a visual caries detection system in epidemiological surveys

Background: In epidemiological surveys, a good reliability among the examiners regarding the caries detection method is essential. However, training and calibrating those examiners is an arduous task because it involves several patients who are examined many times. To facilitate this step, we aimed to propose a laboratory methodology to simulate the examinations performed to detect caries lesions using the International Caries Detection and Assessment System (ICDAS) in epidemiological surveys. Methods: A benchmark examiner conducted all training sessions. A total of 67 exfoliated primary teeth, varying from sound to extensive cavitated, were set in seven arch models to simulate complete mouths in primary dentition. Sixteen examiners (graduate students) evaluated all surfaces of the teeth under illumination using buccal mirrors and ball-ended probe in two occasions, using only coronal primary caries scores of the ICDAS. As reference standard, two different examiners assessed the proximal surfaces by direct visual inspection, classifying them in sound, with non-cavitated or with cavitated lesions. After, teeth were sectioned in the bucco-lingual direction, and the examiners assessed the sections in stereomicroscope, classifying the occlusal and smooth surfaces according to lesion depth. Inter-examiner reproducibility was evaluated using weighted kappa. Sensitivities and specificities were calculated at two thresholds: all lesions and advanced lesions (cavitated lesions in proximal surfaces and lesions reaching the dentine in occlusal and smooth surfaces). Conclusion: The methodology purposed for training and calibration of several examiners designated for epidemiological surveys of dental caries in preschool children using the ICDAS is feasible, permitting the assessment of reliability and accuracy of the examiners previously to the survey´s development.

Reliability-based design optimization strategies based on FORM: a review

In deterministic optimization, the uncertainties of the structural system (i.e. dimension, model, material, loads, etc) are not explicitly taken into account. Hence, resulting optimal solutions may lead to reduced reliability levels. The objective of reliability based design optimization (RBDO) is to optimize structures guaranteeing that a minimum level of reliability, chosen a priori by the designer, is maintained. Since reliability analysis using the First Order Reliability Method (FORM) is an optimization procedure itself, RBDO (in its classical version) is a double-loop strategy: the reliability analysis (inner loop) and the structural optimization (outer loop). The coupling of these two loops leads to very high computational costs. To reduce the computational burden of RBDO based on FORM, several authors propose decoupling the structural optimization and the reliability analysis. These procedures may be divided in two groups: (i) serial single loop methods and (ii) unilevel methods. The basic idea of serial single loop methods is to decouple the two loops and solve them sequentially, until some convergence criterion is achieved. On the other hand, uni-level methods employ different strategies to obtain a single loop of optimization to solve the RBDO problem. This paper presents a review of such RBDO strategies. A comparison of the performance (computational cost) of the main strategies is presented for several variants of two benchmark problems from the literature and for a structure modeled using the finite element method.