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With the application of distributed generators (DGs), microgrids (MGs) have gained much attention. Combined with the distributed communication of networked systems, we investigates the secondary restoration problem in islanded microgrids. The periodic event-triggered (PET) controllers are designed for voltage restoration and frequency restoration with accurate active power allocation, which can naturally avoid Zeno behavior. By means of a common Lyapunov function, a PET protocol is designed that requires only the information of neighbors for event detection. Both event-checking sampling period and event trigger parameter are taken into account to reduce computation and communication redundancy by choosing appropriate parameters. Furthermore, considering the effect of communication delay, sufficient conditions are given to accomplish the secondary control objectives with allowable delays. Switching topologies are considered in an extra discussion. Finally, the effectiveness of the proposed PET control strategies is verified by several MATLAB simulations. • Some distributed secondary periodic event-triggered controllers are designed for islanded microgrids. • Based on periodic event-checking sampling, communication resources and local computation resources are saved. • Switching topologies and communication delays are considered. [ABSTRACT FROM AUTHOR]

The consensus problem is considered for multi-agent systems with disturbances. Three fixed-time prescribed performance methods are proposed to satisfy the transient performance and steady-state performance of multi-agent systems consensus. If the multi-agent systems are affected by matched disturbances, the consensus tracking errors constraints are guaranteed at first. Next, the consensus tracking errors constraints and their change rates constraints are further considered. Moreover, with the help of a fixed-time observer, the consensus tracking errors constraints result is expended to the case of multi-agent systems affected by mismatched disturbances. The proposed methods can provide the satisfactory system performances, including that consensus tracking errors always evolve within predefined bounds, converge to a small closed region containing zero in fixed time and then converge to zero asymptotically. Simulations are provided to verify the effectiveness of the proposed methods. • A problem of fixed-time multi-agent systems consensus is considered. • Both the transient and steady-state performances of multi-agent systems can be guaranteed. • The anti-disturbance controllers can deal with mismatched/matched disturbances. • Three different controllers are available for different cases and performance objectives. [ABSTRACT FROM AUTHOR]

Abstract The remarkable power conversion efficiency of perovskite solar cells (PSCs) is overshadowed by concerns about their stability, and its degradation mechanism remains elusive. PSCs are reported to suffer long-term degradation under real working conditions. In this work, we systematically studied the degradation mechanism of PSCs with various device configurations (planar, meso and inverted device structure) by continuous 12-h day/night cycling tests. The fatigue phenomenon, defined in our previous work, was observed both in planar and meso devices. A relationship between the fatigue instability and device-physics of PSCs is established. Through a comparative analysis of results from day/night cycling tests, bulk/interfacial morphology analysis, and transient photocurrent/photovoltage decay measurements, we identify the fatigue behavior in the day/night cycling tests by a cyclic ion movement mechanism, where ions migrate towards the electrode interfaces under illumination and move back to the bulk in the dark. This cyclic migration of ions generates defects in bulk perovskite without destroying the crystal structure. The present study offers a new approach to evaluate the stability of PSCs, contributing to better understanding of degradation mechanisms that are critically important for applications of this novel photovoltaic technology. Graphical abstract fx1 Highlights • Fatigue stability of different configuration PSCs were studied, and inverted PSCs showed negligible fatigue. • Charge extraction, recombination and accumulation at the interfaces have serious impact on fatigue stability. • The relationship between the fatigue and device-physics of PSCs has been established. • The relationship between fatigue and ionic defects has been identified. [ABSTRACT FROM AUTHOR]

Strain effects on vacancies, electronic states and stability have been disclosed for perovskite structured materials (ABX 3 ) including metal oxides and organic-inorganic hybrids critical for energy storage and generation. Ion substitution has been pursued as an attractive solution to alter the crystallization or induced electronic of organic-inorganic hybrid halide lead perovskite. However, the disorganized structure of perovskite result from inappropriate substitution may cause unwanted phase transition and photo-stability. Herein, we introduce crystallization of restriction ABX 3 composition with moderate zinc (Zn) substitution to obtain the ordered and stable CH 3 NH 3 (Zn:Pb)I 3-x Cl x crystal, which is achieved via releasing lattice strain during an appropriate lattice constriction within BX 6 octahedron. We obtained an unprecedented efficiency of 20.06% under simulated sunlight with facilitating binary metal perovskite of CH 3 NH 3 (1Zn:100Pb)I 3-x Cl x . Our results are important to realize scale up and practical applications of efficient planar perovskite solar cells. [ABSTRACT FROM AUTHOR]

Accurate forecasting of significant wave height (SWH) is crucial for ensuring the safety of marine navigation. To achieve good accuracy, deep learning models need to be trained separately using SWH data from all forecast locations. However, improving the generalizability of SWH prediction models is vital for practical engineering purposes. This paper proposes a training strategy that utilizes multi-point data fusion by using wave data obtained from different locations to construct a training dataset. To verify the feasibility of training strategy, the artificial neural network (ANN), long short-term memory (LSTM), and temporal convolutional network (TCN) models are used to test in China offshore. The RMSE and MAPE of different models with 2h advance forecasts are almost 0.05 and 4%, indicating that the models have good forecasting performance. Additionally, the models exhibit consistency with the model trained solely by single position data, which demonstrates that the training strategy applies to various models. In addition, in sea areas without wave training data, two locations are randomly selected and used in the pre-trained model to predict SWH. The various models demonstrate favorable forecasting results, further demonstrating that the training strategy proposed in this study can enhance the generalizability of models. • The training method based on multi-point data fusion can improve the spatial generalization of the SWH forecasting model. • Using ANN, LSTM, and TCN models for significant wave height forecasting at different locations. • The prediction accuracy of the multi-point data fusion training method and single location training method is the same. • The training method based on multi-point data fusion has good applicability to different deep learning models. [ABSTRACT FROM AUTHOR]

This paper considers an extension of diagonal stability for continuous fractional positive linear systems (FPLS) with the fractional order 0 < α < 1 . Based on diagonal stability of Metzler matrix, an extension that involves the combination of a diagonal positive definite matrix and a skew-symmetric anti-diagonal matrix related a Hurwitz and Metzler matrix is established. Combining this extension and the linear matrix inequalities (LMIs) criteria of stability for fractional order systems (FOS), a necessary and sufficient condition for extension diagonal stability of FPLS is presented. A state feedback controller is given, which ensures the stabilization and positivity of the closed-loop systems. Numerical examples are provided to demonstrate the effectiveness and applicability of the proposed methods. [ABSTRACT FROM AUTHOR]

Stability and lead toxicity issues of inorganic organic halide lead perovskite solar cells have significantly limited their commercial applications. The nontoxic strontium (Sr) can be a good candidate to reduce lead utilization due to their similar ionic radiuses. Here we uncovered the dramatic influence of Sr element substitution on the optoelectronic properties of perovskite films, including up-shifting conduction band edge energy level, increasing exciton binding energy and trap density states due to the isoelectronic impurity of electric neutral substitution. The incorporation of a small content of Sr (a≤0.05) into the CH 3 NH 3 Sr a Pb 1−a I 3−x Cl x crystal lattice can act positively impact on material thermal stability and solar cell device output voltage (~1.11 V). An overall highly photovoltaic efficiency of ~16.3% was achieved with a planar n-i-p structure of ITO/compact TiO 2 /CH 3 NH 3 Sr a Pb 1−a I 3−x Cl x /spiroMeOTAD/Au. Impedance characterization reveals an increased trap states induced by substitution Pb with Sr in the hybrid halide perovskites, and thus provide a deep understanding of the role of external elements on device physics. [ABSTRACT FROM AUTHOR]

Perovskite solar cells can be produced by a solution process and have achieved power conversion efficiency over 20% as well as improving long-term stability, offering great potential for a low cost, high efficiency photovoltaic technology. An increasing effort has been shifted to Lab-to-Fab translation, where device manufacture is accomplished by using a fully scalable printing process. One remarkable bottleneck for upscaling the device is, however, the lack of scalable hole-transport materials (HTMs) that can form the desired morphology during the printing fabrication. In this manuscript, we apply a twisted but fully π-conjugated 2,2′,7,7′-tetrakis(N,N-di- p -methoxyphenyl)amine-9,9′-bifluorenylidene (Bifluo-OMeTAD) into slot-die coated devices, which exhibits excellent film forming properties and outperforms the well-known Spiro-OMeTAD HTM. The improved film forming properties of Bifluo-OMeTAD are achieved via molecular design, with the chemical structure of Bifluo-OMeTAD effectively suppressing crystallization during printing. A power conversion efficiency of 14.7% is achieved in the fully slot-die coated devices based on Bifluo-OMeTAD, outperforming previous reported values for all-printed perovskite solar cells. Therefore, Bifluo-OMeTAD has attractive potential to replace Spiro-OMeTAD for the large scale roll-to-roll production of fully slot-die coated perovskite solar cells. [ABSTRACT FROM AUTHOR]

The simple planar configuration of organic–inorganic hybrid perovskite solar cells produced by a solution coating process has great potential to be a low-cost and high efficiency photovoltaic technology. However planar perovskite films produced by “normal” spin coating usually show a dendritic grain morphology giving many gaps in the film, resulting in poor coverage of the substrate and thus a low power conversion efficiency. Here a facile gas-assisted solution processing technique is reported that has changed the kinetics of nucleation and crystal growth of the perovskite during the spin coating, producing very uniform perovskite thin films consisting of densely packed single crystalline grains. This microstructure is an ideal candidate for the p – i – n solar cell device. Planar perovskite solar cells constructed from these films produced a highly reproducible average power conversion efficiency of 15.7±0.7%. The highest efficiency achieved was 17.0% with a slightly lower steady-state value of 16.5% at the maximum power output of the solar cell. [ABSTRACT FROM AUTHOR]

Ternary blend has been an effective strategy for achieving high efficiency in organic solar cells (OSCs). Herein, a non-fullerene small molecule acceptor (C8-DTC) was synthesized and added to the PM6: Y6 system as a third component. By adding 10% of C8-DTC as the second acceptor in the PM6:Y6 system, an impressive power conversion efficiency of 17.52% was achieved with simultaneously increased open-circuit voltage, short-circuit current-density, and fill factor. The reduced voltage loss was due to the lowered non-radiative recombination loss in comparison with the binary device. It was also found that a small amount of C8-DTC in the PM6:Y6 blend resulted in enhanced charge separation and charge transport by providing possible extra channels of hole extraction. And the ternary system formed a good phase separation and favored bi-continuous transport network, which is more conducive to balance the electron and hole transport. The results indicate that the ternary system formed by C8-DTC as the third component is an effective method to improve the performance of the PM6:Y6 based OSCs. A new small molecule acceptor C8-DTC enhanced the power conversion efficiency of PM6:Y6 based ternary organic solar cells to 17.52%. Image 1 • A new non-fullerene acceptor C8-DTC was proven to be an effective third component in ternary organic solar cells. • A high power conversion efficiency of 17.52% was achieved with addition of C8-DTC into PM6: Y6 system. • Small amount of C8-DTC in the PM6:Y6 blend enhances charge separation and provides channels of charge extraction. [ABSTRACT FROM AUTHOR]

Wide bandgap perovskite solar cells (PSCs) are a key component for the realization of highly efficient tandem solar cells. To simultaneously improve the efficiency and stability is still a big challenge. Herein, phenylmethylamine bromide (PMABr) is employed to modify FA 0.8 Cs 0.2 Pb(I 0.7 Br 0.3) 3 wide bandgap perovskite films. This large cation is incorporated via a post-treatment, which induces a hierarchical layered perovskite and passivates the halide vacancies with the added Br−. The morphology of post-treated films is investigated with synchrotron-based techniques, revealing the formation of a layered structure at the surface, which depends upon the concentration of the PMABr solution. In particular a hierarchical microstructure is observed, consisting of a highly stable pure 2D (n = 1) perovskite layer on top of an efficient quasi-2D (n = 2) perovskite layer that caps an underlying 3D perovskite film. By precisely controlling the surface structure and thickness of the 2D perovskites, wide bandgap (~1.74 eV) PSCs reach an efficiency of 18.5% with negligible hysteresis and a stabilized efficiency of 17.9%. Furthermore, the device moisture stability is also significantly enhanced after the post-treatment, indicating that the post-treatment with PMABr is a viable processing method to achieve both efficient and stable wide bandgap PSCs. Image 1 • A hierarchical layered structure of 2D/3D interface is developed to improve the performance of perovskite solar cells. • A novel phenylmethylamine bromide (PMABr) salt is employed to finely construct the hierarchical layered structure. • A high efficiency of 18.5% of wide bandgap perovskite solar cells is achieved, with negligible hysteresis and improved stability. [ABSTRACT FROM AUTHOR]

• Introduce dynamic model of four-station rotary tool holder. • Calculate the vertical restoring force of rough trapezoidal tooth and screw spiral surfaces. • Experimentally investigate the natural vibration characteristics under various preloads. • Predict vibration response and capture abundant nonlinear behavior. Four-station rotary tool holder on a lathe is fabricated to achieve transposition operation of turning tools and carry the violent cutting force prior to feed system. Its dynamic characteristic has a potential influence on the structural dynamics and cutting stability of a machine tool. This paper develops a mechanical model for the dynamic characteristic analysis and vibration response prediction. Using the fractal contact theory, the analytical model highlights the rough joint interfacial contact of main components including tool holder body, trapezoidal meshing gear plate and screw shaft. The elastic supports of thrust bearing unit and hollow shaft are also considered. The multi-degree-of-freedom system involving the coupled displacement and piecewise restoring force function is established using lumped mass method. The modal and harmonic excitation tests are performed to investigate the natural property and verify the proposed model. Furthermore, numerical simulation evaluates the effect of external excitation, locking force, fractal parameter, bearing preload and shaft stiffness on dynamic characteristic and stability. The proposed model is promising for the structural optimal design of four-station rotary tool holder. [ABSTRACT FROM AUTHOR]

Highlights: [•] An energy efficient sparse random projection clustering routing data gathering scheme is presented. [•] The optimal cluster heads can be obtained based energy consumption model. [•] The scheme guarantees all cluster heads uniformly distributed approximately. [•] The scheme prolongs the network’s lifetime significantly via experiment comparisons. [ABSTRACT FROM AUTHOR]

An efficient approach for fabrication of novel near-infrared (NIR) absorbing materials has been developed based on stabilization of chromogenic radicals in lipid membranes. Compared with the closed-shell molecules, radicals or radical ions of organic chromophores usually display remarkably red-shifted absorption. However, stabilization and functionalization of these radicals is still a challenging task. Herein, biomimetic membranes were employed as a platform for stabilization and convenient functionalization of chromogenic radicals. NIR optical vesicles can be facilely formed by co-assembly of radical-dominated supramolecular chromophores with surfactants in aqueous solution. The as-formed dye-interbedded vesicles with biomimetic membrane surfaces displays strong NIR absorption and electron spin resonance signals, sensitive photoacoustic response upon NIR excitation, and minimal nonspecific interaction with biological macro-molecules. Furthermore, doping of the chromogenic interlayers to optimize the optical properties and modification of the membrane surfaces for functionalization towards bioanalytical applications can be carried out under ambient conditions. Chromogenic supramolecular radicals were interbedded within biomimetic membranes via self-assembly to form strongly near-infrared absorbing nanovesicles which were of low nonspecific adsorption and easy to be functionalized. Image 1 • NIR absorbing nanovesicles had been facilely fabricated via stabilization of chromogenic radicals in lipid membranes. • Biomimetic lipid membranes were employed as a new platform for stabilization and functionalization of organic radicals. • The vesicles displays strong ESR signals, sensitive NIR photoacoustic response, and minimal nonspecific interaction. • This work represents an approach for developing biological applications of functional ensembles with low aqueous stability. [ABSTRACT FROM AUTHOR]

Although high efficiencies have been achieved for perovskite solar cells (PSCs), stability issues are still the key barriers for commercial applications. Herein, we carry out a systematic doping of non-radiative alkaline metal ions (Cs, Rb, K, Na, Li) to perovskite, studying their effects on perovskite morphology, electrical stability and performance of PSCs. The hysteresis related stability issues are also investigated at different conditions, such as steady-state power output, aging, repeated voltage sweeping, varied pre-scan voltage bias, etc. It is found the hysteresis becomes much severer at different test conditions for the devices doped with small sized Li and Na. While the subsized Rb and K ions (compared to Cs) doping can significantly enhance the crystallinity of perovskite and reduce the hysteresis that is also more stable. The crystallization, morphologies, time-resolved photoluminescence, electrochemical impedance spectroscopy were conducted to investigate the properties of the doped perovskite films to understand the relationship between the film quality and device performance. With a proper combination of Cs, Rb, K ions doping in PSCs, a high PCE over 20% is achieved with an enhanced electrical stability. Moreover, an over 17% efficiency 7 × 7 cm2 perovskite solar cell module is realized by this strategy, with a certified PCE of 16.5% (aperture area of 20.78 cm2) without hysteresis. [ABSTRACT FROM AUTHOR]

The calculation method of the composite reinforced panel structure's limit load capacity is investigated. A theoretical method is proposed to establish the constitutive equations, which disassembles the reinforced panel into several parts (i.e., skin, web, and flange) and predict the structure's limit load capacity by performing buckling analysis and failure analysis on these parts respectively. The finite element analysis is employed to simulate the instability path of the structure according to cohesive zone model (CZM) and the secondary development in USDFLD (user subroutine to redefine field variables). The accuracy of simulation model is verified by strain assurance criterion. The results are compared with the experimental values, which confirm the reliability and feasibility of the theoretical method and finite element analysis. This study could provide references for the calculation method of limit load capacity and promote composite's application in civil aircraft. • This paper investigates the panel's bearing capacity and proposes a new theoretical analysis method. • In the FEM analysis, the cohesive zone model (CZM) and the secondary development in USDFLD effectively improve the calculation accuracy. • The accuracy of finite element simulation model is verified by strain assurance criterion (SAC). • This paper summarizes the preparation process of the composite specimen under compression load, which could be used as industry standards and provide certain guidance for similar tests. [ABSTRACT FROM AUTHOR]

Abstract: The influence of stiffeners on plate vibration and noise radiation induced by turbulent boundary layers is investigated by wind tunnel measurements. Plates with and without stiffeners are tested under the flow speed of 60m/s, 71m/s and 86m/s, respectively. The stiffeners are set either perpendicular or parallel to the direction of the free stream. Measured vibration and noise levels are compared with theoretical calculations, where wall pressure cross-spectra are described by the Corcos model. For the plates tested, it is evident that stiffeners perpendicular to the direction of the free stream could increase noise radiation, but have almost no influence on vibration level of plates. [Copyright &y& Elsevier]

In this paper, the static compressive mechanical behaviors of carbon fiber reinforced composites (CFRP) single-lap bolted joints under anti-buckling test fixture were studied. Acoustic emission (AE) technology was used to monitor the damage evolution of specimens. X-ray micro-computed tomography (X-ray μCT) was used to evaluate the damage of CFRP single-lap bolted joints. The surface morphology of the holes was studied by field emission scanning electron microscopy (FESEM). An image processing and analyzing method was proposed, which allows the damage of the specimens to be accurately visualized, separated and quantified in 3D. The results show that X-ray μCT characterization technique greatly improves the ability to characterize the damage of CFRP single-lap bolted joints. The squeezing damage of the composite holes caused by the inclination of the bolt is an important factor affecting the bearing capacity of CFRP single-lap bolted joints. [ABSTRACT FROM AUTHOR]