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Four MOFs with mixed ligands, [Zn3(3-BABA)2(bpa)2(H2O)2]n (1), [Cd3(3-BABA)2(bpa)2]n (2), [Cd3(3-BABA)2(bpe)2]n (3), and {[Cd3(3-BABA)2(bib)(DMA)2]·H2O}n (4) (where 3-H3BABA = 4′,4′′′-(((2-carboxyphenyl)azanediyl)bis(methylene))bis(([1,1′-biphenyl]-2-carboxylic acid)), bpa = 4,4′-azopyridine, bpe = 1,2-bis(pyridin-4-yl)ethane, and bib = 1,4-bis(imidazole)butane), have been synthesized. They are characterized by single crystal X-ray diffraction, X-ray powder diffraction (XRPD), thermogravimetric analysis (TGA) and Fourier transform infrared (FT-IR) spectroscopy. In 1, two 3-BABA and two bpa bridge three Zn2+ ions to form a bicyclic [Zn3(3-BABA)2(bpa)2] unit which is further bridged by carboxylate groups with its adjacent units, resulting in a one-dimensional chain. In 2, 3 and 4, the [Cd3(CO2)6] units are bridged by six 3-BABA ligands into a three-dimensional structure. However, the adjacent [Cd3(CO2)6] units in 2 and 3 are doubly-bridged simultaneously by corresponding pyridyl ligands, while the adjacent [Cd3(CO2)6] units in 4 are singly-bridged simultaneously by corresponding pyridyl ligands. The luminescence sensing investigation indicates that compound 1 exhibits extremely sensitive and selective detection of Cu2+ with a detection limit of 0.363 μM, and compounds 2–4 show extremely sensitive and selective detection of Fe3+ with detection limits of 0.539 μM, 0.265 μM, and 0.748 μM, respectively. Competitive experiments in the presence of interfering cations with 1–4 revealed no major change in the quenching efficiency. [ABSTRACT FROM AUTHOR]

Three‐dimensional (3D) woven textile‐reinforced composites have drawn much attention because of their specific geometries, improved composite interlayer strength, and impact‐resistance performance. In this study, three types of 3D woven structures with different binder‐yarn ratios and paths were designed based on a traditional dobby‐weaving loom with a special weft‐interlock structural design. Carbon/aramid fiber‐reinforced plastic (CAFRP) composites with carbon warp, weft, and aramid binder yarns, as well as carbon fiber‐reinforced plastic (CFRP) composites were reinforced using the three types of woven structures and consolidated with epoxy resin. The quasi‐static and dynamic flexural performance of these 3D woven composites were experimentally investigated using a three‐point bending test and a low‐velocity drop‐weight impact test. Nondestructive ultrasonic C‐scan and X‐ray microcomputed tomography were applied to characterize the failure mode of the impacted composites. Woven structure and aramid binder yarn with a coarse count have a coupling effect on the quasi‐static flexural performance of the 3D woven CAFRP composites. A larger volume combined with a smaller through‐thickness waviness degree of aramid binder yarn has a similar effect with a smaller volume combined with a larger waviness degree. Introducing aramid binder yarn in the hybrid composites lowered the quasi‐static flexural performance to a certain extent (0.28%–47.74% and 5.29%–49.63% for flexural modulus and strength, respectively) but increased the impact performance significantly (e.g., increasing 23.6%–92.7% peak‐load values under 6‐J impacts). A larger volume combined with a smaller waviness degree of the aramid binder yarn introduced in these woven structures contributed more to impact‐resistance and damage‐tolerance performance. [ABSTRACT FROM AUTHOR]

Adaptive empirical Fourier decomposition (AEFD) is a recently developed approach of nonstationary signal mode separation. However, it requires to set the spectrum segmentation boundary relying on the users' professional experience ahead of time. In this paper, a novel spectral envelope-based adaptive empirical Fourier decomposition (SEAEFD) method is proposed to improve the performance of AEFD for rolling bearing vibration signal analysis. In the proposed SEAEFD approach, fast Fourier transform (FFT) of the raw signal is calculated to obtain the frequency spectrum at first. Then, the spectral envelope processing is implemented on the spectrum signal obtained by FFT to achieve an adaptive segmentation. In the traditional segmentation method, generally, the minima and midpoints between adjacent extreme points are taken as the spectrum segmentation boundary, in which the obtained frequency band contains more interference components. To achieve the effect of denoising and restrain the noise that existed in the collected vibration signal, SEAEFD is proposed to optimize the spectrum segmentation boundary so that the obtained frequency band contains the least noise components. Lastly, the inverse FFT is used to reconstruct the component signal within each frequency band and the gained signals are termed as Fourier intrinsic mode functions (FIMFs). Therefore, SEAEFD enables a nonstationary signal to be decomposed into several single-component signals with instantaneous frequencies of physical significance. The proposed SEAEFD method is compared with recently developed methods, including EAEFD, AEFD, EWT, VMD and EMD methods, by analyzing the simulation signals and the measured data of rolling bearing. The results indicate that SEAEFD is valid in diagnosing rolling bearing faults and gets a better diagnosis performance than the compared methods. • The envelope processing-based spectrum segmentation method is developed. • A novel nonstationary signal decomposition method termed SEAEFD is developed to improve the performance of AEFD. • SEAEFD is compared with AEFD, EAEFD, EWT, VMD and EMD through analyzing the simulated and measured signals. • The effectiveness and superiority of SEAEFD in identify the local faults of rolling bearing are verified. [ABSTRACT FROM AUTHOR]

The structural parameters of multibell underreamed anchors play a crucial role in anchoring performance. The parameters of multibell underreamed anchor investigations are helpful when exploring optimized anchor structures. Based on the results of small-scale physical modelling tests, two types of multibell underreamed anchors were adopted under vertical uplifting loads. Numerical investigations were employed to study the effect of bell spacing, underream structure and bell dimension on the ultimate uplift bearing capacity. After an analysis of the anchorage mechanism, the anchoring efficiency was evaluated by the anchoring force provided by the unit concrete usage of the anchor, and the structural parameter λ equal to the surface area ratios of the expanded bell cone to the straight shaft between bells was defined. Then, the anchoring efficiency optimized structural parameters were presented. An analysis of model tests and simulation results showed that compared to concave bell surfaces, the convex shape could enhance the ultimate bearing capacity of a multibell underreamed anchor. There is an optimal value for the spacing of neighbouring bells, and there are three models of mechanisms for multibell anchors pulling out. When λ ∈ [1, 1.8], the multibell anchors can perform most efficiently to achieve their structural advantages. [ABSTRACT FROM AUTHOR]