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Because of the extensive use of long‐span structures in modern engineering, much attention has been given to the extent to which ground motion phase‐lags affect the internal forces of such structures. In this paper, this problem is studied from the aspect of random seismic analysis, i.e. the random seismic responses of long‐span structures are explored with the phase‐lags of the ground joints of the structures taken into account. The earthquake is regarded as a stationary random process. Formulae for calculating the random responses of the structural displacements and internal forces are derived. Numerical examples are presented which illustrate some basic features of such random response, and also show that the ground motion phase‐lags have considerable effects on structural safety analysis.

This paper aims to put forward a nonlinear vibration method for crack detection based on fiber Bragg grating (FBG), which is used to receive the waves in the plate.

First of all, measuring principle of nonlinear vibration technique and FBG sensing principle are introduced. Then nonlinear signal spectrum is analyzed to reveal various models of nonlinear vibration, and modal analysis of the plate structure is performed to lay the foundation for the later experiment. This approach is the cross-modulation effect from a persistent excitation to the receipt signal.

The experimental system is built and its results are in agreement with theoretical analysis, and show that this nonlinear vibration method based on FBG sensor is sensitive to crack damage.

Taking the board structure as the object, a new attempt by nonlinear vibration detection with FBG sensor has been investigated.

Proposes a new approach for analysing the stationary random response of complex structures located in a non‐homogeneous stochastic field. The approach is a kind of complete CQC method because the cross‐correlation terms between both the participant modes and the ground joint excitations are included in the response calculations. Also takes into account the effect of the loss of coherency between ground joints.

Super304H steel is a new fine-grained austenitic heat-resistant stainless steel developed in recent years, and it is widely used in high temperature section superheater and reheater tubes of ultra-supercritical thermal power units’ boiler. Currently intergranular corrosion (IGC) has occurred in a few austenitic stainless steel tubes in ultra-supercritical units and led to boiler leakage. The purpose of this paper is to find a nondestructive method to quickly and easily detect IGC of austenitic stainless steel tube.

This paper uses the nonlinear characteristics of ultrasonic propagation in steel tube to detect the IGC of Super304H tube.

The experimental results show that the nonlinear coefficient generally increases sensitively with the degree of IGC; hence, the nonlinear coefficient can be used to assess IGC degree of tubes, and the nonlinear coefficient measurement method is repeatable for the same tube.

A theory of how IGC would affect the ultrasonic signals and lead to a nonlinear response needs further research.

A nondestructive method to quickly and easily detect IGC is provided.

Using ultrasonic nonlinear coefficient to assess IGC degree of tubes is a new try.

This paper provides a new way to test IGC.

Parallel factor analysis (PARAFAC) coupled with support-vector machine (SVM) was carried out to identify and discriminate between the fluorescence spectroscopies of coconut water brands.

PARAFAC was applied to reduce three-dimensional data of excitation emission matrix (EEM) to two-dimensional data. SVM was applied to discriminate between six commercial coconut water brands in this study. The three largest variation data from fluorescence spectroscopy were extracted using the PARAFAC method as the input data of SVM classifiers.

The discrimination results of the six commercial coconut water brands were achieved by three SVM methods (Ga-SVM, PSO-SVM and Grid-SVM). The best classification accuracies were 100.00%, 96.43% and 94.64% for the training set, test set and CV accuracy.

The above results indicate that fluorescence spectroscopy combined with PARAFAC and SVM methods proved to be a simple and rapid detection method for coconut water and perhaps other beverages.