Error Scenarios Research Articles

The assimilation of horizontal line‐of‐sight wind information into the ECMWF data assimilation and forecasting system. Part II: The impact of degraded wind observations

Single‐component wind observations have been assimilated into the ECMWF data assimilation system. Various Observing System Experiments have been performed in order to estimate the impact of such information in numerical weather prediction. The investigations on the impact of the horizontal line‐of‐sight wind on the ECMWF analysis and forecast system is described in a two‐part article. Part I evaluates the impact of wind observations with respect to mass observations and the impact of assimilating different single wind components versus wind vector information. Part II assesses the forecast system performance in the presence of varying levels of random and systematic error in the line‐of‐sight wind measurements. The aim is to understand the sensitivity of weather forecasts with respect to possible observation error scenarios of the Doppler Wind Lidar (DWL) measurements from the Aeolus mission. It was found that even small wind observation biases (of the order of 1 m s−1) can deteriorate the forecast quality by 3–4% in terms of mean integrated total energy of the 24 h forecast error. This is particularly true for observation biases in the Tropics, in the upper troposphere and lower stratosphere. A 2 m s−1 bias degrades the forecasts by 15%. The increase of the line‐of‐sight random errors (from 25 to 100%) adds only 1–2% forecast skill degradation.

Thermomechanical assessment of the effects of a jaw-beam angle during beam impact on Large Hadron Collider collimators

The correct functioning of a collimation system is crucial to safely and successfully operate high-energy particle accelerators, such as the Large Hadron Collider (LHC). However, the requirements to handle high-intensity beams can be demanding, and accident scenarios must be well studied in order to assess if the collimator design is robust against possible error scenarios. One of the catastrophic, though not very probable, accident scenarios identified within the LHC is an asynchronous beam dump. In this case, one (or more) of the 15 precharged kicker circuits fires out of time with the abort gap, spraying beam pulses onto LHC machine elements before the machine protection system can fire the remaining kicker circuits and bring the beam to the dump. If a proton bunch directly hits a collimator during such an event, severe beam-induced damage such as magnet quenches and other equipment damage might result, with consequent downtime for the machine. This study investigates a number of newly defined jaw error cases, which include angular misalignment errors of the collimator jaw. A numerical finite element method approach is presented in order to precisely evaluate the thermomechanical response of tertiary collimators to beam impact. We identify the most critical and interesting cases, and show that a tilt of the jaw can actually mitigate the effect of an asynchronous dump on the collimators. Relevant collimator damage limits are taken into account, with the aim to identify optimal operational conditions for the LHC.

Unbiased regression estimation under correlated linkage errors

Linkage errors can occur when probability‐based methods are used to link records from two or more distinct data sets corresponding to the same target population. Recent research on allowing for these errors when carrying out regression analysis based on linked data assumes that the linkage errors are independent when more than two data sets are used to generate these data. In this paper, we extend these results to accommodate the more realistic scenario of dependent linkage errors. Our simulation results show that an incorrect assumption of independent linkage errors can lead to insufficient linkage error bias correction, while an approach that allows for correlated linkage errors appears to overcome this problem. Copyright © 2015 John Wiley & Sons, Ltd.

Computerised physician order entry-related medication errors: analysis of reported errors and vulnerability testing of current systems

ImportanceMedication computerised provider order entry (CPOE) has been shown to decrease errors and is being widely adopted. However, CPOE also has potential for introducing or contributing to errors.ObjectivesThe objectives of...

Error disclosure and family members’ reactions: Does the type of error really matter?

ObjectiveTo describe how Italian clinicians disclose medical errors with clear and shared lines of responsibility. MethodsThirty-eight volunteers were video-recorded in a simulated conversation while communicating a medical error to a simulated family member (SFM). They were assigned to a clear responsibility error scenario or a shared responsibility one. Simulations were coded for: mention of the term “error” and apology; communication content and affect using the Roter Interaction Analysis System. SFMs rated their willingness to have the patient continue care with the clinician. ResultsClinicians referred to an error and/or apologized in 55% of the simulations. The error was disclosed more frequently in the clear responsibility scenario (p<0.02). When the “error” was explicitly mentioned, the SFM was more attentive, sad and anxious (p≤0.05) and less willing to have the patient continue care (p<0.05). Communication was more patient-centered (p<0.05) and affectively dynamic with the SFMs showing greater anxiety, sadness, attentiveness and respectfulness in the clear responsibility scenario (p<0.05). ConclusionsDisclosing errors is not a common practice in Italy. Clinicians disclose less frequently when responsibility is shared and indicative of a system failure. Practice implicationsTraining programs to improve disclosure practice considering the type of error committed should be implemented.

Accurate Bolt Tightening Using Model-Free Fuzzy Control for Wind Turbine Hub Bearing Assembly

In the modern wind turbine industry, one of the core processes is the assembly of the bolt-nut connections of the hub, which requires tightening bolts and nuts to obtain well-distributed clamping force all over the hub. This force deals with nonlinear uncertainties due to the mechanical properties and it depends on the final torque and relative angular position of the bolt/nut connection. This paper handles the control problem of automated bolt tightening processes. To develop a controller, the process is divided into four stages, according to the mechanical characteristics of the bolt/nut connection: a Fuzzy Logic Controller (FLC) with expert knowledge of tightening process and error detection capability is proposed. For each one of the four stages, an individual FLC is designed to address the highly non-linearity of the system and the error scenarios related to that stage, to promptly prevent and avoid mechanical damage. The FLC is implemented and real time executed on an industrial PC and finally validated. Experimental results show the performance of the controller to reach precise torque and angle levels as well as desired clamping force. The capability of error detection is also validated.

Study on Wide-area Integrated Impedance Protection WIIP Algorithm

Wide-area integrated impedance protection (WIIP) algorithm based on wide-area measurement system is proposed for the purpose of improving the reliability and sensibility of fault component identification of wide-area protection. Two commonly used methods nowadays in wide-area protection are the current differential protection (CDP) and the directional pilot protection (DPP). The CDP, though responsive to all types of system faults, is subject to the distributed capacitance and earth resistance of transmission line; the DPP, which is easy to implement and does not need much traffic, is subject to system oscillations, conversion failure, and two phases operation. Integrating the advantages of these two algorithms, WIIP is obtained by evaluating in virtue of the ratio of the average voltages to the sum of all incoming and outgoing currents at each protected objects. The advantages of WIIP are verified by the fault analysis of two-terminal system and multi-terminal system. The research results show that WIIP presented in this paper is more preferable than CDP in the aspect of the sensitivity and DPP in the aspect of the dependability. The simulation effects can be obtained by using WIIP method applied in the case of abnormal operations of relay protections, circuit breakers, measurement error scenarios and substation DC failure. Keywords: Centralized system architecture, fault component identification, integrated impedance, wide-area protection.

Relevance-based partial reliability in wireless sensor networks

Wireless sensor networks can provide valuable information for a lot of measurement, tracking, surveillance, automation, and general-purpose monitoring applications. Information as humidity, temperature, pressure, infrared images, and noises will be sensed and packetized for distribution over the network, but corruption during transmission may compromise the accuracy of the retrieved information and even put people in danger. In fact, the sensed data may have different relevancies for the applications, altering the impact of packet corruptions. We propose a relevance-based partially reliable transmission approach to provide data delivery with different reliability guaranties, exploiting the relevancies of transmitted data when choosing the proper error recovery service. In this context, some error scenarios are investigated, considering different configurations of error bursts. We expect that the proposed partially reliable transmission mechanism can save energy over the network while assuring acceptable quality for sensing monitoring.

Predictors of healthcare professionals' attitudes towards family involvement in safety-relevant behaviours: a cross-sectional factorial survey study.

ObjectivesTo investigate predictors of healthcare professionals’ (HCPs) attitudes towards family involvement in safety-relevant behaviours.DesignA cross-sectional fractional factorial survey that assessed HCPs’ attitudes towards family involvement in two error scenarios relating to hand hygiene and medication safety. Each survey comprised two randomised vignettes that described the potential error, how the family member communicated with the HCP about the error and how the HCP responded to the family member’s question.Setting5 teaching hospitals in London, the Midlands and York. HCPs were approached on a range of medical and surgical wards.Participants160 HCPs (73 doctors; 87 nurses) aged between 21 and 65 years (mean 37) 102 were female.Outcome measuresHCP approval of family member’s behaviour; HCP reaction to the family member; anticipated effects on the family member–HCP relationship; HCP support for being questioned about hand hygiene/medication; affective rating responses.ResultsHCPs supported family member's intervening (88%) but only 41% agreed this would have positive effects on the family member/HCP relationship. Across vignettes and error scenarios the strongest predictors of attitudes were how the HCP (in the scenario) responded to the family member and whether an error actually occurred. Doctors (vs nurses) provided systematically more positive affective ratings to the vignettes.ConclusionsImportant predictors of HCPs’ attitudes towards family members’ involvement in patient safety have been highlighted. In particular, a discouraging response from HCP’s decreased support for family members being involved and had strong perceived negative effects on the family member/HCP relationship.

Determining reserve requirements in DK1 area of Nord Pool using a probabilistic approach

Allocation of electricity reserves is the main tool for transmission system operators to guarantee a reliable and safe real-time operation of the power system. Traditionally, a deterministic criterion is used to establish the level of reserve. Alternative criteria are given in this paper by using a probabilistic framework where the reserve requirements are computed based on scenarios of wind power forecast error, load forecast errors and power plant outages. Our approach is first motivated by the increasing wind power penetration in power systems worldwide as well as the current market design of the DK1 area of Nord Pool, where reserves are scheduled prior to the closure of the day-ahead market. The risk of the solution under the resulting reserve schedule is controlled by two measures: the LOLP (Loss-of-Load Probability) and the CVaR (Conditional Value at Risk). Results show that during the case study period, the LOLP methodology produces more costly and less reliable reserve schedules, whereas the solution from the CVaR-method increases the safety of the overall system while decreasing the associated reserve costs, with respect to the method currently used by the Danish TSO (Transmission System Operator).

An Incorporated Voting Strategy on Majority and Score- based Fuzzy Voting Algorithms for Safety-Critical Systems

Triple Modular Redundancy (TMR) is usually used to increase safety and the reliability of safety-critical systems where three identical segments are used in identical and the ultimate outcome is reached using voting techniques. Fault masking is one of the main techniques to improve the normal actions of a range of safety-critical techniques. Some commercial areas which implement such techniques include process control, transport, and atomic power place and army programs. Integrated Voter for majority and weighted-average used to provide for a fault masking capability in safety-critical systems [1]. The Majority voting gives a high level of safety and the weighted-average offers a good level of availability. If integrated these two gives a good level of safety in Majority voting not in integrated voting. Here propose a new voting algorithm for faulty masking taking the disadvantage of previous algorithm. In this Incorporating Majority voting and score based fuzzy voting schemes. Safety performance is evaluated by running proposed, Majority and score based fuzzy voting on a triple modular redundant (TMR) system for 10000 voting cycles in various error scenarios. Experimental results show that proposed fuzzy Voter is given a higher safety than other two voting algorithms.

Implication of spot position error on plan quality and patient safety in pencil-beam-scanning proton therapy.

To quantitatively and systematically assess dosimetric effects induced by spot positioning error as a function of spot spacing (SS) on intensity-modulated proton therapy (IMPT) plan quality and to facilitate evaluation of safety tolerance limits on spot position. Spot position errors (PE) ranging from 1 to 2 mm were simulated. Simple plans were created on a water phantom, and IMPT plans were calculated on two pediatric patients with a brain tumor of 28 and 3 cc, respectively, using a commercial planning system. For the phantom, a uniform dose was delivered to targets located at different depths from 10 to 20 cm with various field sizes from 2(2) to 15(2) cm(2). Two nominal spot sizes, 4.0 and 6.6 mm of 1 σ in water at isocenter, were used for treatment planning. The SS ranged from 0.5 σ to 1.5 σ, which is 2-6 mm for the small spot size and 3.3-9.9 mm for the large spot size. Various perturbation scenarios of a single spot error and systematic and random multiple spot errors were studied. To quantify the dosimetric effects, percent dose error (PDE) depth profiles and the value of percent dose error at the maximum dose difference (PDE [ΔDmax]) were used for evaluation. A pair of hot and cold spots was created per spot shift. PDE[ΔDmax] is found to be a complex function of PE, SS, spot size, depth, and global spot distribution that can be well defined in simple models. For volumetric targets, the PDE [ΔDmax] is not noticeably affected by the change of field size or target volume within the studied ranges. In general, reducing SS decreased the dose error. For the facility studied, given a single spot error with a PE of 1.2 mm and for both spot sizes, a SS of 1σ resulted in a 2% maximum dose error; a SS larger than 1.25 σ substantially increased the dose error and its sensitivity to PE. A similar trend was observed in multiple spot errors (both systematic and random errors). Systematic PE can lead to noticeable hot spots along the field edges, which may be near critical structures. However, random PE showed minimal dose error. Dose error dependence for PE was quantitatively and systematically characterized and an analytic tool was built to simulate systematic and random errors for patient-specific IMPT. This information facilitates the determination of facility specific spot position error thresholds.

Performance evaluation of WirelessHART networks using a new network simulator 3 module

Nowadays, wireless communication is a tendency in industrial environments, enabling the addition of new applications and saving resources when compared to their wired counterparts. In this context, the WirelessHART specification is emerging as a solution for the last mile connection. Despite its high degree of applicability, a WirelessHART network faces some challenges. Some of the most challenging problems are its reliability, energy consumption, and interference from the environment, issues which involve the lower layers. In order to enable performance evaluations in a low cost and scalable way, we propose a new NS-3 module for the WirelessHART physical layer including an error model (Gilbert/Elliot), station positioning, signal attenuation and energy consumption. Furthermore, the module permits configuring each link with different fault probabilities, allowing more accurate simulations. For validation, the scheduling and routing approaches were statically configured assuming different topologies and probabilistic error scenarios already validated in the literature.

Adaptive error detection for HDR/PDR brachytherapy: guidance for decision making during real-time in vivo point dosimetry.

This study presents an adaptive error detection algorithm (AEDA) for real-time in vivo point dosimetry during high dose rate (HDR) or pulsed dose rate (PDR) brachytherapy (BT) where the error identification, in contrast to existing approaches, does not depend on an a priori reconstruction of the dosimeter position. Instead, the treatment is judged based on dose rate comparisons between measurements and calculations of the most viable dosimeter position provided by the AEDA in a data driven approach. As a result, the AEDA compensates for false error cases related to systematic effects of the dosimeter position reconstruction. Given its nearly exclusive dependence on stable dosimeter positioning, the AEDA allows for a substantially simplified and time efficient real-time in vivo BT dosimetry implementation. In the event of a measured potential treatment error, the AEDA proposes the most viable dosimeter position out of alternatives to the original reconstruction by means of a data driven matching procedure between dose rate distributions. If measured dose rates do not differ significantly from the most viable alternative, the initial error indication may be attributed to a mispositioned or misreconstructed dosimeter (false error). However, if the error declaration persists, no viable dosimeter position can be found to explain the error, hence the discrepancy is more likely to originate from a misplaced or misreconstructed source applicator or from erroneously connected source guide tubes (true error). The AEDA applied on two in vivo dosimetry implementations for pulsed dose rate BT demonstrated that the AEDA correctly described effects responsible for initial error indications. The AEDA was able to correctly identify the major part of all permutations of simulated guide tube swap errors and simulated shifts of individual needles from the original reconstruction. Unidentified errors corresponded to scenarios where the dosimeter position was sufficiently symmetric with respect to error and no-error source position constellations. The AEDA was able to correctly identify all false errors represented by mispositioned dosimeters contrary to an error detection algorithm relying on the original reconstruction. The study demonstrates that the AEDA error identification during HDR/PDR BT relies on a stable dosimeter position rather than on an accurate dosimeter reconstruction, and the AEDA's capacity to distinguish between true and false error scenarios. The study further shows that the AEDA can offer guidance in decision making in the event of potential errors detected with real-time in vivo point dosimetry.

Simulation-based assessment to evaluate cognitive performance in an anesthesiology residency program.

Problem solving in a clinical context requires knowledge and experience, and most traditional examinations for learners do not capture skills that are required in some situations where there is uncertainty about the proper course of action. We sought to evaluate anesthesiology residents for deficiencies in cognitive performance within and across 3 clinical domains (operating room, trauma, and cardiac resuscitation) using simulation-based assessment. Individual basic knowledge and cognitive performance in each simulation-based scenario were assessed in 47 residents using a 15- to 29-item scenario-specific checklist. For every scenario and item we calculated group error scenario rate (frequency) and individual (resident) item success. For all analyses, alpha was designated as 0.05. Postgraduate year (PGY)-3 and PGY-4 residents' cognitive items error rates were higher and success rates lower compared to basic and technical performance in each domain tested (P < .05). In the trauma and resuscitation scenarios, the cognitive error rate by PGY-4 residents was fairly high (0.29-0.5) and their cognitive success rate was low (0.5-0.68). The most common cognitive errors were anchoring, availability bias, premature closure, and confirmation bias. Simulation-based assessment can differentiate between higher-order (cognitive) and lower-order (basic and technical) skills expected of relatively experienced (PGY-3 and PGY-4) anesthesiology residents. Simulation-based assessments can also highlight areas of relative strength and weakness in a resident group, and this information can be used to guide curricular modifications to address deficiencies in tasks requiring higher-order processing and cognition.

Wide-Area Backup Protection Algorithm Based on Earth Impedance Comparison Principle

A novel algorithm is proposed for the purpose of improving the reliability and sensibility of fault component identification of wide area backup protection. The algorithm, called earth impedance comparison protection (EICP), is realized by comparing the ratios of different nodes, and the ratio is obtained by the bus voltage to the differential current. The advantages of EICP are verified in this paper using the measurement function of wide-area measurement system. The results of case studies show that EICP is superior to the current differential protection in terms of the sensitivity and to the directional pilot protection in terms of the dependability. The satisfactory results can be obtained when the EICP method is applied in the event of abnormal operations of protective relays and circuit breakers, measurement error scenarios or substation DC failure.

House-of-security approach to measurement in analytical chemistry: quantification of human error using expert judgments

A new technique for quantification of human errors in chemical analysis using expert judgments is described. This technique is based on the house-of-security approach developed recently in the field of safety and security for prevention of terrorist and criminal attacks against an organization. The following relative quantification parameters (expressed in %) are proposed in the technique: (a) likelihood score of human error in a chemical analytical measurement/testing method, (b) severity score of human error for reliability of the test results, (c) importance score of a component of a laboratory quality system, and (d) effectiveness score of the quality system as a whole in preventing/blocking human error. As an example, 34 scenarios of human error in pH measurement of groundwater are discussed and quantified.

Convergence Property of the Measurement Gross Error Correction in Power System State Estimation, Using Geometrical Background

In this paper it is shown that once the measurements with gross errors are detected and identified, the geometrical approach to recover gross errors in power system state estimation, as we have previously proposed, is a convergent process. For the purpose of correcting the measurement gross errors, the measurement residuals are computed, and then the measurement gross errors are composed. For the detection and identification of the measurements with gross errors, the composed measurement error in the normalized form <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$(CME^{N})$</tex></formula> is used. The measurement magnitude corrections otherwise are performed using the composed normalized error <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$(CNE)$</tex></formula> . To support the thesis that, after the detection and identification of the measurements containing gross errors, the measurement correction is a convergent procedure, the generalization of the largest normalized error test is also provided. A two-bus power network is used to show in a didactic way the behavior of the gross error correction. The IEEE 14-bus system and the 45-bus equivalent of Brazil south are used to perform the tests for the multiple measurement gross errors case. Many gross error scenarios with different redundancy levels, for multiple gross error situations, have been tested. The measurement correction is made one at a time.

Impacts of measured data uncertainty on urban stormwater models

Summary Assessing uncertainties in models due to different sources of errors is crucial for advancing urban drainage modelling practice. This paper explores the impact of input and calibration data errors on the parameter sensitivity and predictive uncertainty by propagating these errors through an urban stormwater model (rainfall runoff model KAREN coupled with a build-up/wash-off water quality model). Error models were developed to disturb the measured input and calibration data to reflect common systematic and random uncertainties found in these types of datasets. A Bayesian approach was used for model sensitivity and uncertainty analysis. It was found that random errors in measured data had minor impact on the model performance and sensitivity. In general, systematic errors in input and calibration data impacted the parameter distributions (e.g. changed their shapes and location of peaks). In most of the systematic error scenarios (especially those where uncertainty in input and calibration data was represented using ‘best-case’ assumptions), the errors in measured data were fully compensated by the parameters. Parameters were unable to compensate in some of the scenarios where the systematic uncertainty in the input and calibration data were represented using extreme worst-case scenarios. As such, in these few worst case scenarios, the model’s performance was reduced considerably.

Predictors of health care professionals' attitudes towards involvement in safety‐relevant behaviours

Patients can make valuable contributions towards promoting the safety of their health care. Health care professionals (HCPs) could play an important role in encouraging patient involvement in safety-relevant behaviours. However, to date factors that determine HCPs' attitudes towards patient participation in this area remain largely unexplored. To investigate predictors of HCPs' attitudes towards patient involvement in safety-relevant behaviours. A 22-item cross-sectional fractional factorial survey that assessed HCPs' attitudes towards patient involvement in relation to two error scenarios relating to hand hygiene and medication safety. Four hospitals in London Two hundred sixteen HCPs (116 doctors; 100 nurses) aged between 21 and 60 years (mean: 32): 129 female. Approval of patient's behaviour, HCP response to the patient, anticipated effects on the patient-HCP relationship, support for being asked as a HCP, affective rating response to the vignettes. HCPs elicited more favourable attitudes towards patients intervening about a medication error than about hand sanitation. Across vignettes and error scenarios, the strongest predictors of attitudes were how the patient intervened and how the HCP responded to the patient's behaviour. With regard to HCP characteristics, doctors viewed patients intervening less favourably than nurses. HCPs perceive patients intervening about a potential error less favourably if the patient's behaviour is confrontational in nature or if the HCP responds to the patient intervening in a discouraging manner. In particular, if a HCP responds negatively to the patient (irrespective of whether an error actually occurred), this is perceived as having negative effects on the HCP-patient relationship.