Probabilistic Structural Model Updating with Modal Flexibility Using a Modified Firefly Algorithm

Structural model updating is one of the most important steps in structural health monitoring, which can achieve high-precision matching between finite element models and actual engineering structures. In this study, a Bayesian model updating method with modal flexibility was presented, where a modified heuristic optimization algorithm named modified Nelder–Mead firefly algorithm (m-NMFA) was proposed to find the most probable values (MPV) of model parameters for the maximum a posteriori probability (MAP) estimate. The proposed m-NMFA was compared to the original firefly algorithm (FA), the genetic algorithm (GA), and the particle swarm algorithm (PSO) through the numerical illustrative examples of 18 benchmark functions and a twelve-story shear frame model. Then, a six-story shear frame model test was performed to identify the inter-story stiffness of the structure in the original and the damage states, respectively. By comparing the two, the position and extent of damage were accurately found and quantified in a probabilistic manner. In terms of optimization, the proposed m-NMFA was powerful to find the MPVs much faster and more accurately. In the incomplete measurement case, only the m-NMFA achieved target damage identification results. The proposed Bayesian model updating method has the advantages of high precision, fast convergence, and strong robustness in MPV finding and the ability of parameter uncertainty quantification

Prognostic value of the early lung ultrasound B-line score for postoperative pulmonary insufficiency in patients undergoing thoracic surgery: an observational study

Abstract Background Postoperative pulmonary insufficiency (PPI) is an important contributor to morbidity and mortality after thoracic surgery. Lung ultrasound is a reliable tool for assessing respiratory function. We sought to determine the clinical value of the early lung ultrasound B-line score for predicting changes in pulmonary function after thoracic surgery. Methods Eighty-nine patients undergoing elective lung surgery were included in this study. The B-line score was determined 30 min after removal of the endotracheal tube, and the PaO2/FiO2 ratio was recorded 30 min after extubation and on the third postoperative day. Patients were divided into normal (PaO2/FiO2 ≥ 300) and PPI (PaO2/FiO2 < 300) groups according to their PaO2/FiO2 ratios. A multivariate logistic regression model was used to identify independent predictors of postoperative pulmonary insufficiency. Receiver operating characteristic (ROC) analysis was performed for significantly correlated variables. Results Eighty-nine patients undergoing elective lung surgery were included in this study. We evaluated 69 patients in the normal group and 20 in the PPI group. Patients conforming to NYHA class 3 at administration were significantly more represented in the PPI group (5.8 and 55%; p < 0.001). B-line scores were significantly higher in the PPI group than in the normal group (16; IQR 13–21 vs. 7; IQR 5–10; p < 0.001). The B-line score was an independent risk factor (OR = 1.349 95% CI 1.154–1.578; p < 0.001), and its best cutoff value for predicting PPI was 12 (sensitivity: 77.5%; specificity: 66.7%). Conclusions Lung ultrasound B-line scores 30 min after extubation are effective in predicting early PPI in patients undergoing thoracic surgery. Trial registration This study was registered with the Chinese Clinical Trials Registry (ChiCTR2000040374)

Rock mechanics parameters

Rock mechanics parameters for simulation in the paper

Data from: Plastic limit bearing calculation of blasting-roof in deep hole mining and its applications

In order to solve the problem that blasting-roof thickness was hard to determine in deep hole mining, the plastic bearing calculation method of blasting-roof was proposed. Aim at typical boundary conditions of blasting-roof, mechanical analysis model of plastic bearing was built. The external work and internal work of blasting-roof under plastic limit state were calculated. Based on virtual work principle, the limit bearing formulas of blasting-roof under various boundary conditions were derived. Taking a VCR stope as the object, the safe blasting-roof thickness was determined as 6m by derived formula (considering safety coefficient). Numerical model of stope was constructed by Surpac-Flac3D technique, while blasting-roof stability was simulated under different thickness. The variation of simulated indexes (stress, plastic zone volume) prove that theoretical calculation is reliable. The plastic bearing calculation method can provide a new way for determining blasting-roof thickness in deep hole mining

Newly Discovered Action of HpTx3 from Venom of Heteropoda venatoria on Nav1.7 and Its Pharmacological Implications in Analgesia

It has been reported that Heteropodatoxin3 (HpTx3), a peptidic neurotoxin purified from the venom of the spider species Heteropoda venatoria, could inhibit Kv4.2 channels. Our present study newly found that HpTx3 also has potent and selective inhibitory action on Nav1.7, with an IC50 of 135.61 &plusmn; 12.98 nM. Without effect on the current&ndash;voltage (I-V) relationship of Nav1.7, HpTx3 made minor alternation in the voltage-dependence of activation and steady-state inactivation of Nav1.7 (4.15 mV and 7.29 mV, respectively) by interacting with the extracellular S3&ndash;S4 loop (S3b&ndash;S4 sequence) in domain II and the domain IV of the Nav channel subtype, showing the characteristics of both pore blocker and gate modifier toxin. During the interaction of HpTx3 with the S3b&ndash;S4 sequence of Nav1.7, the amino acid residue D in the sequence played a key role. When administered intraperitoneally or intramuscularly, HpTx3 displayed potent analgesic activity in a dose-dependent manner in different mouse pain models induced by formalin, acetic acid, complete Freund&rsquo;s adjuvant, hot plate, or spared nerve injury, demonstrating that acute, inflammatory, and neuropathic pains were all effectively inhibited by the toxin. In most cases HpTx3 at doses of &ge; 1mg/kg could produce the analgesic effect comparable to that of 1 mg/kg morphine. These results suggest that HpTx3 not only can be used as a molecular probe to investigate ion channel function and pain mechanism, but also has potential in the development of the drugs that treat the Nav1.7 channel-related pain

Data from: Plastic limit bearing calculation of blasting-roof in deep hole mining and its applications

In order to solve the problem that blasting-roof thickness was hard to determine in deep hole mining, the plastic bearing calculation method of blasting-roof was proposed. Aim at typical boundary conditions of blasting-roof, mechanical analysis model of plastic bearing was built. The external work and internal work of blasting-roof under plastic limit state were calculated. Based on virtual work principle, the limit bearing formulas of blasting-roof under various boundary conditions were derived. Taking a VCR stope as the object, the safe blasting-roof thickness was determined as 6m by derived formula (considering safety coefficient). Numerical model of stope was constructed by Surpac-Flac3D technique, while blasting-roof stability was simulated under different thickness. The variation of simulated indexes (stress, plastic zone volume) prove that theoretical calculation is reliable. The plastic bearing calculation method can provide a new way for determining blasting-roof thickness in deep hole mining

Probabilistic Updating of Structural Models for Damage Assessment Using Approximate Bayesian Computation

A novel probabilistic approach for model updating based on approximate Bayesian computation with subset simulation (ABC-SubSim) is proposed for damage assessment of structures using modal data. The ABC-SubSim is a likelihood-free Bayesian approach in which the explicit expression of likelihood function is avoided and the posterior samples of model parameters are obtained using the technique of subset simulation. The novel contributions of this paper are on three fronts: one is the introduction of some new stopping criteria to find an appropriate tolerance level for the metric used in the ABC-SubSim; the second one is the employment of a hybrid optimization scheme to find finer optimal values for the model parameters; and the last one is the adoption of an iterative approach to determine the optimal weighting factors related to the residuals of modal frequency and mode shape in the metric. The effectiveness of this approach is demonstrated using three illustrative examples

Structural Model Identification Using a Modified Electromagnetism-Like Mechanism Algorithm

A modified electromagnetism-like mechanism (EM) algorithm is proposed to identify structural model parameters using modal data. EM is a heuristic algorithm, which utilizes an attraction&ndash;repulsion mechanism to move the sample points towards the optimal solution. In order to improve the performance of original algorithm, a new local search strategy, new charge and force calculation formulas, new particle movement and updating rules are proposed. The test results of benchmark functions show that the modified EM algorithm has better accuracy and faster convergence rate than the original EM algorithm and the particle swarm optimization (PSO) algorithm. In order to investigate the applicability of this approach in parameter identification of structural models, one numerical truss model and one experimental shear-building model are presented as illustrative examples. The identification results show that this approach can achieve remarkable parameter identification even in the case of large noise contamination and few measurements. The modified EM algorithm can also be used to solve other optimization problems