A direct estimation method for expanding incomplete experimental mode shapes is presented. The approach adopts a hybrid vector which includes measured data at master degrees of freedom (dofs) and ...constant values at slave dofs. The constant values are refined by a set of mode-correction factors. Modelling errors between the analytical model and tested structure are also considered by introducing a series of model-correction factors. Initial-guess values of the mode-correction factors are used to decouple the coupled constructed equations, and an iterative technique for solving these equations is proposed. The results from a five-degree-of-freedom mass–spring system indicate that the proposed approach provided a better performance than the commonly used existing expansion methods and can reliably estimate unmeasured components of mode shapes, even in cases with limited modal measurements and severe measurement noise. The performance of the proposed method was also investigated using real measurements from a steel cantilever-beam experiment. Experimental data were measured by 20 accelerometers mounted at the cantilever beam: among these accelerometers, three of these were assumed to be measured, and the others were used to check the estimation accuracy of the proposed method. The results show that the unmeasured components in the mode shapes were properly estimated by implementing the proposed method, even for high-frequency modes.
► We propose a new method dealing with spatially incomplete experimental mode shapes. ► A hybrid vector is defined and values at slave coordinates are iterative modified. ► Model-correction factors are defined to take into account modelling errors. ► Convergence is verified by numerical and experimental studies and demonstrated well. ► The approach can expand mode shapes more accurately and reliably than existing ones.
This paper presents a modified version of the generalized Kudryashov method aimed at obtaining exact solutions for fractional partial differential equations of Schrödinger type. Firstly, the ...fractional partial differential equations are transformed into a set of ordinary differential equations using the fractional complex transform. Subsequently, a modified version of the generalized Kudryashov method is employed to solve these equations and the obtained results are utilized to derive the traveling wave solutions for fractional partial differential equations of the Schrödinger type. Finally, the graphs resulting from the traveling wave solution are examined, encompassing the analysis of kink waves and singular kink waves.
•A modified version of the generalized Kudryashov method is presented.•Exact solutions to the space–time fractional Schrödinger type equation are obtained.•The obtained solutions are classified as traveling wave, kink waves and singular kink waves.
The feasibility of using millimeter-wave radars for wave observations was investigated in this study. The radars used in this study operate at a center frequency of 77.572 GHz. To investigate the ...feasibility of wave observations and extract one-dimensional and two-dimensional wave spectra, arrays consisting of multiple radar units were deployed for observations in both laboratory and field environments. Based on the data measured with the millimeter-wave radars, one-dimensional wave spectra and two-dimensional wave directional spectra were evaluated using the periodogram method and the Bayesian directional spectrum estimation method (BDM), respectively. Meanwhile, wave parameters such as the significant wave height, wave period, and wave direction were also calculated. Via comparative experiments with a capacitive wave height meter in a wave tank and RADAC’s WG5-HT-CP radar in an offshore field, the viability of using millimeter-wave radars to observe water waves was validated. The results indicate that the one-dimensional wave spectra measured with the millimeter-wave radars were consistent with those measured with the mature commercial capacitive wave height meter and the WG5-HT-CP wave radar. Via wave direction measurement experiments conducted in a wave tank and offshore environment, it is evident that the wave directions retrieved with the millimeter-wave radars were in good alignment with the actual wave directions.
An improved modal strain energy method is proposed for damage localisation in jacket-type offshore wind turbines by defining a series of stiffness-correction factors that can be employed to calculate ...the modal strain energy (MSE) of the measured model without utilising the stiffness matrix of the finite element model (FEM) as an approximation. The theoretical contribution of this article is that the MSE of the measured model could be estimated with better accuracy, and the advantage of the proposed indicator is that it is more sensitive to damage locations than the traditional MSE method. Numerical studies on a tripod offshore jacket wind turbine reveal that the proposed method could locate the damage positions for jacket-type offshore wind turbines when limited number of lower-order modes is available, even when these modes are spatially incomplete. The performance of the proposed method is also investigated using real measurements from a steel jacket-type offshore wind turbine experiment conducted in a water tank of Ocean University of China. The experimental results demonstrated that the proposed method outperforms the traditional MSE method, and damages in jacket-type offshore wind turbines could be properly located utilising the first two measured modes excited by environmental loadings, such as waves, currents, or the vibration of the wind turbine.
•A new method is proposed for damage localization in jacket-type offshore wind turbines.•The proposed indicator is more sensitive to damage locations.•A series of stiffness-correction factors are defined.•A steel jacket-type offshore wind turbine with 1/15 is constructed.•The method can deal with spatial incompleteness of jacket-type offshore wind turbines.
In order to investigate the wave energy resource, the third-generation wave model SWAN is utilised to simulate wave parameters of the China East Adjacent Seas (CEAS) including Bohai, Yellow and East ...China Sea for the 22 years period ranging from 1990.1 to 2011.12. The wind parameters used to simulate waves are obtained by the Weather Research & Forecasting Model (WRF). The results are validated by observed wave heights of 7 stations. The spatial distributions of wave energy density in the CEAS are analysed under the 22-year largest envelop, mean annual and season averaged wave conditions. Along China east coastal, the largest nearshore wave energy flux occurs along the nearshore zones between Zhoushan Island and south bound of CEAS area. The wave energy resources at Liaodong Peninsula Headland and East Zhoushan Island where economy develops rapidly are also studied in detail. For the two sites, the monthly averaged wave energy features of every year for the 22 years are investigated. The wave energy resources of the two potential sites are characterised in terms of wave state parameters. The largest monthly averaged density for the two sites occurs at Zhoushan Island adjacent sea and amounts to 29 kW/m.
•22-year wave modelling in China East Adjacent Seas is carried out.•The climate of wave energy in China East Adjacent Seas is analyzed.•The largest nearshore wave energy density exists in southern of Korea Peninsula.•Wave energy characteristics of two sites are investigated in detail.
The ultrasonic guided wave technology plays a significant role in the field of non-destructive testing as it employs acoustic waves with the advantages of high propagation efficiency and low energy ...consumption during the inspect process. However, the theoretical solutions to guided wave scattering problems with assumptions such as the Born approximation have led to the poor quality of the reconstructed results. Besides, the scattering signals collected from industry sectors are often noised and nonstationary. To address these issues, a novel physics-informed framework (PIF) for the quantitative reconstruction of defects by means of the integration of the data-driven method with the guided wave scattering analysis is proposed in this paper. Based on the geometrical information of defects and initial results obtained by the PIF-based analysis of defect reconstructions, a deep-learning neural network model is built to reveal the physical relationship between the defects and the noisy detection signals. This learning model is then adopted to assess and characterize the defect profiles in structures, improve the accuracy of the analytical model, and eliminate the impact of the noise pollution in the process of inspection. To demonstrate the advantages of the developed PIF for the complex defect reconstructions with the capability of denoising, several numerical examples are carried out. The results show that the PIF has greater accuracy for the reconstruction of defects in the structures than the analytical method, and provides a valuable insight into the development of artificial intelligence (AI)-assisted inspection systems with high accuracy and efficiency in the fields of structural integrity and condition monitoring.
Pb(II) can cause a hazardous effect on ecosystem and public health due to its high biotoxicity. A polyvinylidene fluoride-type membrane bearing both poly(amino phosphonic acid) and poly(amino ...carboxylic acid) functional groups was fabricated for the purpose of Pb(II) removal from the aqueous solutions. The adsorption behaviors of the fabricated chelating membrane toward Pb(II) were studied by the series of static and continuous adsorption experiments. When the pH, adsorption equilibrium time, initial Pb(II) concentration, and temperature were 5.1, 300 min, 1.0 mmol g−1, and 298 K, respectively, Pb(II) uptake of the membrane was 1.1 mmol g−1. The presence of coexisting metal ions and complexing reagents decreased the Pb(II) uptake. The adsorption kinetic and isotherm adsorption followed pseudo-second-order equation and Langmuir model, respectively; this adsorption process showed a spontaneous and exothermic feature. The bed depth service time and Thomas models were suitable for describing obtained breakthrough curves.
A two-step mode shape expansion methodology is proposed for offshore jacket structures when modelling errors between the finite element model and the tested structure are taken into account and ...estimated in a physical meaningful interval. In the first step, initial guess on mode-correction factors is refined by neglecting these modelling errors; then in the second step, these modelling errors are considered by introducing a series of model-correction factors, which are assigned with physical meanings by using constrained linear least squares technique. Therefore, measured mode shapes can be expanded with an improved convergence performance, and the model-correction factors are estimated within a physical meaningful interval. A three-dimensional five-storey frame structure is firstly employed to investigate the performance of the proposed method, and results show that the approach can reliably expand measured mode shapes with improved convergence performance, and the modelling errors can be estimated with physical meaning. Furthermore, the performance of the approach is also studied by a steel three-dimensional platform, and experimental results demonstrate that mode shapes can be expanded properly when a reference constraint on mode-corrections factors is used based on the mode shape values from the FEM model, and can estimate modelling-correction factors in an expected physical meaningful interval.
► A two-step mode shape expansion method is proposed for offshore structures when modelling errors exist. ► Initial guess on mode-correction factors is refined by neglecting modeling errors. ► Physical meaningful modeling errors are obtained using constrained linear least squares. ► Convergence performance is improved by the refinement of mode-correction factors. ► Physical meaningful mode shape values at slave coordinates can be estimated properly.
The oceans are crucial to human civilization. They provide core support for exploitation and utilization of marine space, resources, and energy. Thus, marine infrastructures are vital to a nation’s ...economic sustainable development. To this end, this article first describes the main challenges in current ocean utilization, and then reviews the China’s ocean engineering progress. As such, six major sectors are evaluated: 1) global climate change and marine environment, 2) comprehensive utilization of marine space, 3) marine transportation infrastructure interconnection, 4) ocean clean energy development and maricultural facilities, 5) ecological crisis and marine engineering countermeasures, and 6) marine infrastructure operation safety and maintenance. Finally, perspectives on future directions of ocean utilization and marine infrastructure construction in China are provided.
With the development of science and technology, traffic perception, communication, information processing, artificial intelligence and the shipping information system have become important in ...supporting the realization of intelligent shipping transportation. Against this background, the Internet of Vessels (IoV) is proposed to integrate all these advanced technologies into a platform to meet the requirements of international and regional transportations. The purpose of this paper is to analyze how to benefit from the Internet of Vessels to improve the efficiency and safety of shipping, and promote the development of world transportation. In this paper, the IoV is introduced and its main architectures are outlined. Furthermore, the characteristics of the Internet of Vessels are described. Several important applications that illustrate the interaction of the Internet of Vessels’ components are proposed. Due to the development of the Internet of Vessels still being in its primary stage, challenges and prospects are identified and addressed. Finally, the main conclusions are drawn and future research priorities are provided for reference and as professional suggestions for future researchers in this field.
PDF
