Adaptive sequential nonlinear LSE for structural damage tracking with incomplete measurements

Parameter identification is very important in structural health monitoring for structural safety and management after emergency event. In practical applications, some external inputs, such as seismic excitations, wind loads, etc. and some structure responses may not be measured or may not be measurable. Herein detail analysis based on adaptive sequential nonlinear least-square estimation with unknown inputs and unknown outputs (ASNLSE-UI-UO) method is developed for effective parameter identification. Simulation studies using a 3-DOF linear system and experimental studies using a 3-DOF shear-beam model with different scenarios of unknown inputs and unknown outputs are carried out to verify the analytical results. Simulation and experimental results demonstrate that this analysis technique for effective parameter identification of ASNLSE-UI-UO method is reasonable and accurate

System identification of rubber-bearing isolators based on experimental tests

Rubber-bearing isolation systems have been used in buildings and bridges. These base isolation systems will become more popular in the future due to their ability to reduce significantly the structural responses induced by earthquakes and other dynamic loads. To ensure the integrity and safety of these base isolation systems, a structural health monitoring system is needed. One important problem in the structural health monitoring is the identification of the system and the detection of damages. This problem is more challenging for the rubberbearing isolation systems because of their nonlinear behavior. In this paper, experimental studies have been conducted for the system identification of nonlinear hysteretic rubberbearings. Experimental tests of a rubber-bearing isolator under El Centro and Kobe earthquakes have been performed. The Bouc-Wen models with 3, 5 and 6 unknown parameters, respectively, have been investigated to represent the hysteretic behavior of rubber-bearing isolators. The extended Kalman filter (EKF) approach has been used to identify the nonlinear parameters of the Bouc-Wen models for the rubber-bearing isolators. Our experimental studies demonstrate that the Bouc-Wen models are capable of describing the nonlinear behavior of rubber-bearing isolators, and that the EKF approach is effective in identifying nonlinear hysteretic parameters

Parameter identification of aircraft thin-walled structures using incomplete measurements

Early parametric identification is critical for the decision making of repair or replacement in order to guarantee structural safety. Nowadays, aircraft thin-walled structures are widely applied in aero-/astronautics areas and their health conditions receive considerable attention. Parameter identification in aircraft thin-walled structures is more challenging because of the structural complexity. In this research, a new time-domain analysis method, the sequential nonlinear least square estimation (SNLSE) method, along with model reduction technique is proposed to identify the parameters of aircraft thin-walled structures using vibration data, which is referred to as the reduced order model based SNLSE approach. Herein, model reduction technique is used to reduce the number of degrees of freedom for conducive to the placement of sensors and high-efficiency calculation by SNLSE method. Simulation and experimental studies have been conducted for the parameter identification of the aluminum thin-walled structure. As demonstrated by simulation and experimental results, the proposed approach using incomplete measurements is very effective in parameter identification of aircraft thin-walled structures

A Rapid Self-Alignment Strategy for a Launch Vehicle on an Offshore Launching Platform

To reduce the impact of offshore launching platform motion and swaying on the self-alignment accuracy of a launch vehicle, a rapid self-alignment strategy, which involves an optimal combination of anti-swaying coarse alignment (ASCA), backtracking navigation, and reverse Kalman filtering is proposed. During the entire alignment process, the data provided by the strapdown inertial navigation system (SINS) are stored and then applied to forward and backtrack self-alignment. This work elaborates the basic principles of coarse alignment and then analyzes the influence of ASCA time on alignment accuracy. An error model was built for the reverse fine alignment system. The coarse alignment was carried out based on the above work, then the state of the alignment system was retraced using the reverse inertial navigation solution and reverse Kalman filtering with the proposed strategy. A cycle-index control function was designed to approximate strict backtracking navigation. Finally, the attitude error was compensated for after the completion of the first and the last forward navigation. To demonstrate the effectiveness of the proposed strategy, numerical simulations were carried out in a scenario of launch vehicle motion and swaying. The proposed strategy can maximize the utilization of SINS data and hence improve the alignment accuracy and further reduce the alignment time. The results show that the fully autonomous alignment technology of the SINS can replace the complex optical aiming system and realize the determination of the initial attitude of a launch vehicle before launch

Geochemical Characteristics and Evaluation Criteria of Overmature Source Rock of the Laiyang Formation in Well LK-1, Riqingwei Basin, Eastern China

Total organic carbon (TOC) and hydrocarbon generation potential (Pg) are essential parameters for the qualitative evaluation of source rock and the basis for evaluating hydrocarbon resources in petroliferous basins. However, there will be some deviations in evaluating hydrocarbon resources of overmature source rock by using TOC and Pg. The super-thick overmature source rock of the Early Cretaceous Laiyang Formation was found in well LK-1, the Riqingwei Basin. To accurately understand the oil and gas potential of the Riqingwei Basin, this paper conducted a systematic organic geochemical analysis of the overmature source rock of the Early Cretaceous Laiyang Formation found in well LK-1. Combined with the results of previous thermal simulation tests on hydrocarbon generation of low-maturity samples in the Jiaolai Basin, the original total organic carbon (TOC0) content of source rock in well LK-1 was recovered and the evaluation criteria of overmature source rock was established. Results: (1) The average TOC content of well LK-1 source-rock samples is 1.25 wt.%, and the average Pg content is 0.11 mg/g. The type of organic matter is mainly type II2, including a small amount of type II1 and type III. The average reflectance of vitrinite (Ro) is 4.35%, which belongs to overmature source rock of a poor–fair level and mixed kerogen. (2) After recovery calculation, these samples’ original hydrocarbon generation potential (Pg0) contents ranged from 0.63 to 108.1 mg/g, with an average value of 6.76 mg/g. Furthermore, the TOC0 contents of the analyzed source-rock samples ranged from 0.62 to 30.6 wt.%, with an average value of 2.01 wt.%. It belongs to fair–good source rock, showing better hydrocarbon generation potential. (3) According to the relationship between the Pg0, Pg and TOC content, the evaluation standard for overmature source rock in well LK-1 was established. Under the evaluation standard of overmature source rock, a source rock with a TOC content exceeding 0.6% and a Pg content greater than 0.1 mg/g can be identified as a good source rock. This paper provides a foundation for the fine classification and evaluation of the overmature source rock of the Riqingwei Basin

Structure, Mechanical and Tribological Properties of MoSN/MoS₂ Multilayer Films

MoSN/MoS2 multilayer films were deposited by a sputtering MoS2 target in alternate Ar and Ar/N2 mixed atmospheres with different nitrogen flow rates. The influence of nitrogen flow rates on the microstructure, mechanical and tribological properties of the prepared films were investigated. The multilayer film exhibited the preferred orientation of (002) plane for MoS2 sublayers and amorphous structure for MoSN sublayers. Introducing N2 into the source gas resulted in a much more compact structure for multilayer films due to the suppression of columnar growth of MoS2 film. With the increase of the nitrogen flow rate, the hardness of the multilayer film firstly increased from 2.3 to 10.5 GPa as the nitrogen flow rate increased from 4 to 10 sccm and then turned downwards to 6.5 GPa at 20 sccm. MoSN/MoS2 film deposited with an optimized microstructure exhibited low friction coefficients below 0.03 and a wear life higher than 1.8×105 revolutions in vacuum. Meanwhile, the optimized film showed an ultralow friction coefficient of 0.004~0.01 and wear rate of 4.7 × 10−7 mm3/N·m in an ultrahigh vacuum. Both the enhanced hardness by N-doping and sustainable formed MoS2 tribofilm contributed to the improved tribological property of MoSN/MoS2 multilayer film

Controllable growth of SnS2 nanostructures on nanocarbon surfaces for Lithium-ion and Sodium-ion storage with high rate capability

Two-dimensional (2D) layered metal dichalcogenides (LMDs) with semiconducting character have been attracting increasing attention in both fundamental studies and various applications. In the case of electrode material design for energy storage, integrating metal dichalcogenides with other conductive phases such as nanocarbons has been widely recognised as an efficient way to simultaneously achieve good electrochemical activity and conductivity. However, controllable growth of metal dichalcogenides on nanocarbons with well-defined structure and efficient interfacial contact is still highly challenging. In this work, we report a new class of SnS2 nanosheets with distinct growth orientations on the surfaces of reduced graphene oxide (RGO) and carbon nanotubes (CNTs). We further demonstrate a spatial confinement strategy to in situ grow SnS2 nanoparticles, which are homogeneously confined within RGO or CNT based porous carbon matrices. Consequently, these resultant 3D architectures demonstrate outstanding rate capability and cycling stability due to their synergistic effect of electrochemically active SnS2 particles and highly conductive carbon matrixes. In particular, the free-standing CNT sponge based composite delivers specific capacities of 741 and 462 mA h g(-1) at 3200 mA g(-1) for Li+ and Na+ storage, respectively, among the best values reported for both lithium ion battery (LIB) and sodium ion battery (NIB) systems. This work not only provides better understanding of the growth mechanisms of metal dichalcogenides on nanocarbons but also opens a new way to construct unique 2D heterostructures for various applications

Comparative Study of Tectonic Evolution and Oil–Gas Accumulation in the Ri-Qing-Wei Basin and the Jiaolai Basin

The Ri-Qing-Wei basin is located in the central Sulu Orogeny on the eastern side of the Tanlu fault zone in eastern Shandong province. To the north, the Jiaonan uplift separates it from the Jiaolai basin, where drilling in the lower Cretaceous sedimentary rock of the Laiyang group has indicated good oil and gas reserves. Drilling in the Ri-Qing-Wei basin, in contrast, is in the preliminary exploration stage. Lingke 1, the only scientific well, is on Lingshan Island on the basin boundary, and it encountered a large set of source rocks 700 m thick. The two basins were comprehensively compared and analyzed based on comprehensive fieldwork, drilling, core data, seismic profiling, sedimentary filling sequence, tectonic evolution history, basin burial history, geothermal history, and geochemical characteristics of the source rocks. The results showed three things: (1) from the late Jurassic to the early Cretaceous (the Laiyang period), subduction of the paleo-Pacific plate under the Eurasian plate delaminated the lithospheric mantle of the Sulu Orogeny, thus forming a series of passive continental rift basins. Of these, the Ri-Qing-Wei is central and the Jiaolai is its branch. After the active rift stage in the Qingshan period and the depression stage in the Wangshi period, the burial depth of the source rocks in the Ri-Qing-Wei basin was up to 6000 m, while the maximum burial depth in the Jiaolai basin was about 3000 m. The paleogeotemperature of both basins exceeded 125 °C, indicating that the source rocks were very mature. (2) A comprehensive comparison of their geochemical characteristics—organic matter abundance, type, and maturity—showed that both basins have oil-generating potential. It is worth noting that the magmatic activity in the Qingshan period had a positive effect on the evolution of the source rocks but was not the key factor: burial depth was. (3) Oil and gas failed to accumulate in the Jiaolai basin because they were destroyed by the lateral tectonic activities. During the right-lateral strike-slip stage (50 ± 5 Ma) during the late Wangshi, the Jiaolai basin was strongly uplifted over a range of more than 1000 m by the Tanlu and Wulian-Mouji fault zones along the boundary. The Wangshi group, as a cap rock, was eroded, and oil and gas overflowed along the fault that reached the surface. The late Wangshi period uplift of the Ri-Qing-Wei basin was less than 1000 m because the source rock was deeper, and the reverse faults in the basin were sealed well. The uplift did little damage to the oil in the Ri-Qing-Wei basin. Above all, tectonic evolution was the main controlling factor of oil accumulation in the study area, and the layers of the Laiyang group in the Ri-Qing-Wei basin have oil and gas potential, making it a prospective target for unconventional offshore oil and gas exploration