Equivalent Standard Deviation to Convert High-Reliability Model to Low-Reliability Model for Efficiency of Sampling-Based RBDO

2011 ◽  
Author(s):  
Ikjin Lee ◽  
Kyung K. Choi ◽  
David Gorsich
Keyword(s):  
Standard Deviation ◽  
Optimum Design ◽  
High Reliability ◽  
Score Function ◽  
Probability Of Failure ◽  
Reliability Model ◽  
Efficient Computation ◽  
Exact Probability ◽  
Current Design ◽  
And Performance

This study presents a methodology to convert an RBDO problem requiring very high reliability to an RBDO problem requiring relatively low reliability by increasing input standard deviations for efficient computation in sampling-based RBDO. First, for linear performance functions with independent normal random inputs, an exact probability of failure is derived in terms of the ratio of the input standard deviation, which is denoted by δ. Then, the probability of failure estimation is generalized for any random input and performance functions. For the generalization of the probability of failure estimation, two coefficients need to be determined by equating the probability of failure and its sensitivity with respect to the standard deviation at the current design point. The sensitivity of the probability of failure with respect to the standard deviation is obtained using the first-order score function for the standard deviation. To apply the proposed method to an RBDO problem, a concept of an equivalent standard deviation, which is an increased standard deviation corresponding to the low reliability model, is also introduced. Numerical results indicate that the proposed method can estimate the probability of failure accurately as a function of the input standard deviation compared to the Monte Carlo simulation results. As anticipated, the sampling-based RBDO using the surrogate models and the equivalent standard deviation helps find the optimum design very efficiently while yielding relatively accurate optimum design which is close to the one obtained using the original standard deviation.

Design Sensitivity Method for Sampling-Based RBDO With Varying Standard Deviation

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
Hyunkyoo Cho ◽  
K. K. Choi ◽  
Ikjin Lee ◽  
David Lamb
Keyword(s):  
Standard Deviation ◽  
Design Variable ◽  
Score Function ◽  
Random Variable ◽  
Probability Of Failure ◽  
Design Sensitivity ◽  
Mean Value ◽  
Reliability Based Design ◽  
The Mean ◽  
Sensitivity Method

Conventional reliability-based design optimization (RBDO) uses the mean of input random variable as its design variable; and the standard deviation (STD) of the random variable is a fixed constant. However, the constant STD may not correctly represent certain RBDO problems well, especially when a specified tolerance of the input random variable is present as a percentage of the mean value. For this kind of design problem, the STD of the input random variable should vary as the corresponding design variable changes. In this paper, a method to calculate the design sensitivity of the probability of failure for RBDO with varying STD is developed. For sampling-based RBDO, which uses Monte Carlo simulation (MCS) for reliability analysis, the design sensitivity of the probability of failure is derived using a first-order score function. The score function contains the effect of the change in the STD in addition to the change in the mean. As copulas are used for the design sensitivity, correlated input random variables also can be used for RBDO with varying STD. Moreover, the design sensitivity can be calculated efficiently during the evaluation of the probability of failure. Using a mathematical example, the accuracy and efficiency of the developed design sensitivity method are verified. The RBDO result for mathematical and physical problems indicates that the developed method provides accurate design sensitivity in the optimization process.

Local Calibration of Pavement Mechanistic-Empirical Faulting Reliability using Pavement Management Data

2021 ◽  
pp. 036119812110013
Author(s):  
Lucio Salles de Salles ◽  
Lev Khazanovich
Keyword(s):  
Model Calibration ◽  
Prediction Models ◽  
Plain Concrete ◽  
Performance Model ◽  
Pavement Management ◽  
Pavement Design ◽  
Reliability Model ◽  
Transverse Joint ◽  
Design Characteristics ◽  
And Performance

The Pavement ME transverse joint faulting model incorporates mechanistic theories that predict development of joint faulting in jointed plain concrete pavements (JPCP). The model is calibrated using the Long-Term Pavement Performance database. However, the Mechanistic-Empirical Pavement Design Guide (MEPDG) encourages transportation agencies, such as state departments of transportation, to perform local calibrations of the faulting model included in Pavement ME. Model calibration is a complicated and effort-intensive process that requires high-quality pavement design and performance data. Pavement management data—which is collected regularly and in large amounts—may present higher variability than is desired for faulting performance model calibration. The MEPDG performance prediction models predict pavement distresses with 50% reliability. JPCP are usually designed for high levels of faulting reliability to reduce likelihood of excessive faulting. For design, improving the faulting reliability model is as important as improving the faulting prediction model. This paper proposes a calibration of the Pavement ME reliability model using pavement management system (PMS) data. It illustrates the proposed approach using PMS data from Pennsylvania Department of Transportation. Results show an increase in accuracy for faulting predictions using the new reliability model with various design characteristics. Moreover, the new reliability model allows design of JPCP considering higher levels of traffic because of the less conservative predictions.

scholarly journals Code Calibration of the Eurocodes

2021 ◽  
Vol 11 (12) ◽  
pp. 5474
Author(s):  
Tuomo Poutanen
Keyword(s):  
High Reliability ◽  
High Accuracy ◽  
Variable Load ◽  
Reliability Model ◽  
Safety Factors ◽  
Rounding Errors ◽  
Code Calibration ◽  
Load Factors ◽  
Characteristic Values

This article addresses the process to optimally select safety factors and characteristic values for the Eurocodes. Five amendments to the present codes are proposed: (1) The load factors are fixed, γG = γQ, by making the characteristic load of the variable load changeable, it simplifies the codes and lessens the calculation work. (2) Currently, the characteristic load of the variable load is the same for all variable loads. It creates excess safety and material waste for the variable loads with low variation. This deficiency can be avoided by applying the same amendment as above. (3) Various materials fit with different accuracy in the reliability model. This article explains two options to reduce this difficulty. (4) A method to avoid rounding errors in the safety factors is explained. (5) The current safety factors are usually set by minimizing the reliability indexes regarding the target when the obtained codes include considerable safe and unsafe design cases with the variability ratio (high reliability/low) of about 1.4. The proposed three code models match the target β50 = 3.2 with high accuracy, no unsafe design cases and insignificant safe design cases with the variability ratio 1.07, 1.03 and 1.04.

scholarly journals Parameter Determination and Ion Current Improvement of the Ion Current Sensor Used for Flame Monitoring

Sensors ◽  
2021 ◽  
Vol 21 (3) ◽  
pp. 697
Author(s):  
Hanqing Xu ◽  
Weijun Fan ◽  
Jianwei Feng ◽  
Peiliang Yan ◽  
Shuchan Qi ◽  
...  
Keyword(s):  
Contact Area ◽  
High Reliability ◽  
Ion Current ◽  
Parameter Determination ◽  
Current Sensor ◽  
Vertical Position ◽  
Excitation Voltage ◽  
Burner Exit ◽  
And Performance ◽  
Flame Monitoring

Flame monitoring of industrial combustors with high-reliability sensors is essential to operation security and performance. An ion current flame sensor with a simple structure has great potential to be widely used, but a weak ion current is the critical defect to its reliability. In this study, parameters of the ion current sensor used for monitoring flames on a Bunsen burner are suggested, and a method of further improving the ion current is proposed. Effects of the parameters, including the excitation voltage, electrode area, and electrode radial and vertical positions on the ion current, were investigated. The ion current grew linearly with the excitation voltage. Given that the electrodes were in contact with the flame fronts, the ion current increased with the contact area of the cathode but independent of the contact area of the anode. The smaller electrode radial position resulted in a higher ion current. The ion current was insensitive to the anode vertical position but largely sensitive to the cathode vertical position. Based on the above ion current regularities, the sensor parameters were suggested as follows: The burner served as a cathode and the platinum wire acted as an anode. The excitation voltage, anode radial and vertical positions were 120 V, 0 mm, and 6 mm, respectively. The method of further improving the ion current by adding multiple sheet cathodes near the burner exit was proposed and verified. The results show that the ion current sensor with the suggested parameters could correctly identify the flame state, including the ignition, combustion, and extinction, and the proposed method could significantly improve the magnitude of the ion current.

Study on efficient computation and performance of AV-based reduced-rank filtering

2005 ◽  
Vol 22 (2) ◽  
pp. 153-160
Author(s):  
Bin Xu ◽  
Chenyang Yang ◽  
Shiyi Mao
Keyword(s):  
Efficient Computation ◽  
Reduced Rank ◽  
And Performance

scholarly journals Self-efficacy and performance of the roundhouse kick in taekwondo

2014 ◽  
Vol 9 (2) ◽  
pp. 97 ◽  
Author(s):  
Isaac Estevan ◽  
Octavio Álvarez ◽  
Coral Falcó ◽  
Isabel Castillo
Keyword(s):  
Self Efficacy ◽  
Impact Force ◽  
High Reliability ◽  
Sport Performance ◽  
Total Response Time ◽  
Psychological Training ◽  
Males And Females ◽  
And Performance ◽  
Performance Results ◽  
The Relationship

Development of self-efficacy scales allows the analysis of athletes’ perceptions and examination of the relationship between perception and performance. The aim of this paper was to: (1) develop a specific self-efficacy scale in a taekwondo task, the roundhouse kick, and (2) analyse the sport performance and its relationship with two self-efficacy scales (specific and general) outcomes according to the athletes’ gender.<strong> </strong>Forty-three taekwondo athletes (33 male and 10 female) participated in this study. The Physical (PSE) and Specific (RKSES) self-efficacy scales were administered. Performance data (impact force and total response time) were acquired by athletes kicking twice to an instrumented target. Results showed that the specific self-efficacy scale has high reliability and is able to predict sport performance in males and females. Males had higher self-efficacy scores and also higher performance results than females. Females’ taekwondo psychological training should be focus on improving their self-efficacy perception in order to increase their performance in the roundhouse kick. This specific self-efficacy scale for the taekwondo roundhouse kick offers empirical information to coaches, sport psychologists and researchers that allow them to predict athletes’ sport performance in the roundhouse kick.

scholarly journals Performance Prediction Equation for 2000 m Youth Indoor Rowing Using a 100 m Maximal Test

Biology ◽  
2021 ◽  
Vol 10 (11) ◽  
pp. 1082
Author(s):  
Luiz Felipe da Silva ◽  
Paulo Francisco de Almeida-Neto ◽  
Dihogo Gama de Matos ◽  
Steven E. Riechman ◽  
Victor de Queiros ◽  
...  
Keyword(s):  
Mathematical Model ◽  
Reliability Index ◽  
High Reliability ◽  
Low Cost ◽  
Time Trial ◽  
Prediction Equation ◽  
Daily Routine ◽  
Negative Consequences ◽  
Maximum Effort ◽  
And Performance

Background: The exhaustive series of tests undergone by young athletes of Olympic rowing prior to important competitions imply loads of physical stress that can ultimately impact on mood and motivation, with negative consequences for their training and performance. Thus, it is necessary to develop a tool that uses only the performance of short distances but is highly predictive, offering a time expectancy with high reliability. Such a test must use variables that are easy to collect with high practical applicability in the daily routine of coaches. Objective: The objective of the present study was to develop a mathematical model capable of predicting 2000 m rowing performance from a maximum effort 100 m indoor rowing ergometer (IRE) test in young rowers. Methods: The sample consisted of 12 male rowing athletes in the junior category (15.9 ± 1.0 years). A 100 m time trial was performed on the IRE, followed by a 2000 m time trial 24-h later. Results: The 2000 m mathematical model to predict performance in minutes based on the maximum 100 m test demonstrated a high correlation (r = 0.734; p = 0.006), strong reliability index (ICC: 0.978; IC95%: [0.960; 0.980]; p = 0.001) and was within usable agreement limits (Bland -Altman Agreement: −0.60 to 0.60; 95% CI [−0.65; 0.67]). Conclusion: The mathematical model developed to predict 2000 m performance is effective and has a statistically significant reliability index while being easy to implement with low cost.

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