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The acoustic topological waveguide (ATW) hosting topologically protected waveguide modes provides a unique opportunity for achieving large-scale sound transport with robustness. However, prevailing ATWs are typically designed by forward-designed sonic crystals (SCs) based on physical intuitions, unavoidably leading to restricted bandwidths. Here, using the inverse-designed SCs with maximized topological bandgaps, we construct broadband ATWs based on both the quantum spin Hall effect and the quantum valley Hall effect. Broadband large-scale transportation, spin-locked one-way transportation, and the squeezing effect of acoustic waves are demonstrated. This study ushers a new path for designing topological devices with broadband performance for large-scale acoustic wave transportation. [ABSTRACT FROM AUTHOR]

• Introducing a novel density measurement utilizing shared nearest neighbors, enhancing the assessment of data point density. • Developing an advanced K-means enhancement technique to dynamically determine cluster quantity and initial cluster center. • Integration of density-based and partition-based clustering methodologies, refining the K-means method's performance. • Achievement of peak performance in clustering outcomes via the proposed K-means modification. • Synergizing with various feature selection strategies for optimal clustering results proves its superior adaptability. User clustering is crucial for tapping the flexibility of the load side and realizing dynamic management of power loads in new power system. K-means method is widely used in clustering analysis due to its simplicity, high efficiency, and scalability, but it needs to specify the number of clusters in advance, and is sensitive to the initial clustering centers. The current initialization method does not take into account the neighborhood distribution of the data points, and the direct use of data that has undergone dimensionality reduction processing leads to inaccurate selection of the initial clustering centers. To address the above problems, a new K-means improvement method that takes into account the initialization problem and the adaptive determination of the number of clusters: K-means clustering method based on nearest-neighbor density matrix is proposed in this paper. The method improves the efficiency of nearest neighbor search by building a K-D tree, and enhances the performance of unsupervised classification by utilizing the adaptive selection strategy of the number of clusters and the initial clustering centers selection algorithm. The proposed method is applied to real datasets, and its effectiveness is assessed by calculating three clustering evaluation metrics of the clustering results in comparison with several existing initialization and clustering methods. The experimental results show that the method proposed in this paper has higher stability and better clustering performance than existing clustering methods. [ABSTRACT FROM AUTHOR]

We present an innovative rainbow piezoelectric energy harvesting approach that harnesses the untapped potential of the topological meta-device for robust and efficient vibration energy trapping and conversion, from its theoretical rudiments, through design of the device to experimental validation. The rigorously designed meta-device features a series of second-order phononic topological insulators to host topologically protected corner states of different eigenfrequencies. By tailoring and tuning various corner sites, multi-frequency vibrations along a specially engineered channel that supports the edge states spanning these frequencies can be trapped into different corner sites. The vibrational energy is thus converted into electrical energy efficiently using strategically placed piezoelectric harvesters. Experimental results reveal the capability of the device in trapping targeted vibration, in which vibrational energy can be trapped into different corner sites in terms of its frequency, leading to an interesting rainbow energy conversion. This new approach not only implements high-efficiency energy harvesting but also offers enhanced design flexibilities for diverse applications by spatially separating vibrational frequencies. [Display omitted] • A vibrational energy harvester based on high-order topological insulators is developed. • Rainbow energy trapping and harvesting are experimentally achieved. • High-efficiency and robust energy harvesting is demonstrated. [ABSTRACT FROM AUTHOR]

Second-order photonic topological insulators (SPTIs) featured with topological edge and corner states provide an intriguing way for steering light in integrated optics. However, existing SPTIs have narrow bulk gaps for tightly confining topological edge and corner states. In this paper, we propose a bi-directional evolutionary structural optimization (BESO) method to inversely engineer SPTIs in C 3 -symmetric lattices. At first, we maximize the first band gap of a photonic crystal (PC) enforced with C 3 symmetry. Then, the topological phase transition is achieved by inverting the optimized PC. Highly localized topological edge and corner states are formed at the boundary and corner between the optimized PC and its inversion-symmetry partner. The bandwidth of the topological edge state for TE modes achieves 44.9%, exceeding two times of the current record. The robust of the topological corner states is further demonstrated. Our work provides a new route for designing SPTIs, paving the way towards their practical application. • An inverse design method for designing second-order photonic topological insulators in C 3 -symmetric lattices is developed. • Topological nontrivial and trivial photonic crystals with a record-breaking size of the overlapped band gap are designed. • Second-order photonic topological insulators with tightly localized corner states are created. • The robustness of corner states is demonstrated. [ABSTRACT FROM AUTHOR]

• An intelligent method for designing second-order phoxonic topological insulators is developed. • SPTIs with customized topological bandgaps are created. • Customized corner states for both phononic and photonic modes are achieved. Second-order phononic and photonic topological insulators hosting topologically protected edge and corner states provide opportunities for the robust manipulation of elastic/acoustic and electromagnetic (EM) waves, respectively. Despite their potential, the development of second-order phoxonic topological insulators, which combine functionalities of second-order phononic and photonic topological insulators, remains largely unexplored. Herein, we design second-order phoxonic topological insulators (SPTI) with customized bandgaps. An inverse design approach is proposed to engineer phoxonic crystals (PCs) featuring customized odd-order phononic and photonic bandgaps simultaneously. Topological phase transition is induced by translating the primitive unit cell (UC) of the inverse-designed PC with half of the lattice constant horizontally and vertically. Thereafter, the SPTI is constructed by juxtaposing the primitive and translated UCs to form a corner between them. Multiple SPTIs, capable of manipulating both acoustic and EM waves, as well as those governing elastic and EM waves, are created. Our work paves the way for customized SPTIs with tailored bandgaps to support diverse phononic and photonic corner states. Meanwhile, the designed SPTIs also provide a platform to design the higher-order topological optomechanical devices. [Display omitted] [ABSTRACT FROM AUTHOR]

Acoustic topological insulators (ATIs) with topological states that are insensitive to defects and impurities offer a robust way to steer acoustic waves. However, current ATIs in square lattice only host topological interface states within one bulk bandgap, restricting their multiband applications. Here, we design the ATI, made of glide-symmetric sonic crystals (SCs), hosting multiband topological interface states within multiple bulk bandgaps. First, SCs restricted with glide and mirror symmetries are inversely designed to host multiple bulk bandgaps. Then, the ATI with multiband helical interface states is constructed by selecting two kinds of unit cells (UCs) from the inverse-designed SC and arranging them to form an interface. Both dual-band and triple-band ATIs are designed and experimentally validated. The total size of interface states hosted by the triple-band ATI is about 8.5 times of the record. Besides, by exploiting the mismatch of frequency windows of interface states at the horizontal and vertical interfaces, we realize acoustic demultiplexers for routing interface states. Our work suggests a route to engineering multiband ATIs, having promising applications in designing novel acoustic devices for multiband information processing and communication. [ABSTRACT FROM AUTHOR]

• Multi-frequency Dirac cones are created in micro-perforated phononic plates with split-ring resonators (SRRs). • Tri-band topological edge and corner modes are experimentally verified. • The emergence of valley-shaped degeneracy bands is insensitive to the geometric parameters. To develop phononic topological insulators (PTIs) with time reversal invariance, phononic crystals (PCs) are elaborately configurated to ensure the lattice symmetry and meanwhile to open the complete band gap. Particularly, a multi-band PTI requires more complex architecture than its single-band counterpart, leading to extra difficulty in implementation and poor manufacturability of PCs. Here, we present a straightforward and generic design strategy, to realize multi-band PTIs in micro-perforated phononic plates. Rather than using complex surface-mounted or embedded scatterers, the novel phononic plate is micro-perforated with a type of fan-shaped split-ring resonators (SRRs), the multi-modal resonances of which under constrained lattice symmetry induce multiple Dirac degeneracies in flexural-wave dispersions at different frequency scales. The multi-band topological phase transitions are observed, and triple topological band gaps are caused when rotating micro-perforated slots properly. Experimental results agree well with numerical simulation results, both demonstrating triband valley edge-state propagation of flexural waves. In addition, we also prove that the developed valley PTIs enable the second-order corner modes of flexural waves within the corresponding topological band gaps. Parametric studies further reveal that the emergence of the valley-shaped Dirac degeneracy bands in the developed PTI is insensitive to the plate thickness and slots parameters, and more than three Dirac cones exist in flexural-wave dispersions. The developed micro-perforated plates with SRRs provides a convenient platform for enabling multi-band PTIs with various symmetries, facilitating applications of multi-frequency topological effects of elastic waves in a cost-effective way. [Display omitted] [ABSTRACT FROM AUTHOR]

Highlights • Noncontact current measurement method with high-performance magnetic sensors. • Accuracy improvement with the combination of two effective arrangements of magnetic sensor array. • Effect of the displacement of conductor and sensors are considered and quantitatively discussed. • Tests with laboratory experiments are performed for protective measurement purpose. Abstract The development of smart grid calls for pervasive deployment of current measurement in the power transmission and distribution system, serving for monitoring, control and protection purpose. However, traditional methods fail to measure current with bandwidth from direct current to kHz and are inconvenient to install or dismount. In this paper, a novel current measurement method with a clamp-like structure is proposed to alleviate the magnetic interference from random sources. This method is based on a special magnetic sensor array which consists of three pairs of sensors. In each pair, the sensitive directions of the sensors are opposite. Besides, positioning calibration of the conductor under measurement is considered in order to reduce the error contributed by the displacement uncertainty of the conductor. The proposed design is tested by numerical simulation and finite element analysis (FEA). For peak current up to 500 A, the maximum error is 0.6532%. A prototype is then implemented and tested in laboratory experiments to demonstrate the performance of the proposed approach for measurement and protective purpose. From the results, the maximum error is 1.73%, which is compatible with standard IEC 60044-8:2002 accuracy classes for protective electronic current transformer. [ABSTRACT FROM AUTHOR]

Abstract The Dirac-like cones underlie many unique properties of photonic crystals (PhCs). This paper aims to design fabrication-friendly PhCs with Dirac-like cones for transverse magnetic (TM) modes and transverse electric (TE) modes at different specific frequencies. By maximizing the minimum of a collection of the local density of states corresponding to different judiciously selected sources, this paper demonstrates that Dirac-like cones formed by the degeneracy of a doubly degenerate mode and a single mode at different desired frequencies are successfully obtained. The exotic wave manipulation properties associated with Dirac-like cones, such as cloaking, wavefront shaping and tunneling through bent channels, are exhibited based on the optimized structures. This paper also demonstrates that the proposed method could be used for the design of PhCs with one Dirac-like cone at ω , and one monopolar band at 2 ω at the Γ point, and PhCs with third order Dirac-like cones, which have potential applications in nonlinear optics. All topological patterns of the optimized PhCs are reported and have regular and smooth features, meaning they can be readily fabricated. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

• Multiband second-order sonic topological insulators (SSTIs) are created. • Multiple topological band gaps are customized via inverse design. • The three-band corner states are experimentally validated. The second-order sonic topological insulators (SSTIs) with topologically protected corner states offer promising opportunities for developing novel acoustic devices. However, most of the current SSTIs are designed via trial-and-error and are only able to host the second-order topological phases within a single bandgap, leaving the topic of second-order topological phases within multiple bandgaps rarely studied. Here, we exploit a topology optimization method to customize and optimize multiband SSTIs. To begin with, we create multiple dual-band SSTIs with customizable dual bandgaps for hosting dual-band corner states. On that basis, a three-band SSTI with three bandgaps is constructed for hosting three-band corner states. Experimental validation is performed to prove the existence of the three-band corner states. This study ushers in a route for customizing high-performance multiband SSTIs, and the designed multiband SSTIs have potential for designing robust multiband acoustic devices. [Display omitted] [ABSTRACT FROM AUTHOR]

The propagation of evanescent waves inside phononic band gaps is important for the design of phononic crystals with desirable functionalities. This paper extends the bi-directional evolutionary structure optimization (BESO) method to the design of phononic crystals for maximizing spatial decay of evanescent waves. The optimization objective is to enlarge the minimum imaginary part of wave vectors at a specified frequency. The study is systematically conducted for both out-of-plane and in-plane waves at various frequencies. Numerical examples demonstrate that the proposed optimization algorithm is effective for designing phononic crystals with maximum spatial decay of evanescent waves. Various topological patterns of optimized phononic crystals are given. The results also show that the proposed optimization algorithm can successfully overcome difficulties in opening band gap at desirable frequencies, especially for the complete band gap and multiple band gaps. [ABSTRACT FROM AUTHOR]

• Anisotropic topological phases are created within odd-order bandgaps of topology-optimized photonic crystals. • Highly localized topological edge states are constructed. • Anisotropic transmission of topological edge states is demonstrated. Photonic topological insulators endow flexible manipulation of light with high efficiency and robustness. The majority of previous research concentrated on isotropic topological states, with anisotropic topological states receiving less attention. In this study, we investigate anisotropic topological edge states in two-dimensional photonic systems for both the transverse magnetic (TM) and transverse electric (TE) modes. First, using the topology optimization method, photonic crystals (PCs) with maximized odd-order band gaps, from the first-order to the seventh-order, are created. An anisotropic topological phase transition is then obtained by shifting the primitive unit cell (UC) of the optimized PC along the horizontal direction by half of the lattice constant. Tightly localized anisotropic topological edge states are thus formed at the interface between the primitive and translated UCs. Finally, the transmission properties of the anisotropic topological edge states are numerically demonstrated. Our findings could aid in the development of topological photonic devices that offer reliable directional transmissions and radiations. [ABSTRACT FROM AUTHOR]

This paper provides a study on a novel octagonal multi-cell tube with functionally graded thickness (FGT) under multiple loading angles. First, comparative analysis on the FGT tube and the counterpart tube with uniform thickness(UT) under multiple loading angles reveal that the energy absorption is more superior for the FGT tube when the loading angle exceeds the lower bound of the transition range of the UT tube. Second, parametric study on the FGT tube indicates that thickness gradient exponent and thickness range have significant effect on its crashworthiness. Third, multiobjective optimizations of the FGT tube are conducted, aiming to maximize specific energy absorption(SEA) and minimize initial force(IPF) under multiple loading angles, based upon the Non-dominated sorting genetic algorithm(NAGA-Ⅱ) and RBF technique. The optimized FGT tube demonstrates better crashworthiness than the UT tube in all design cases. These findings can provide valuable guidelines for the design of multi-cell tube with functionally graded thickness under multiple loading angles. [ABSTRACT FROM AUTHOR]

Nanofluid boiling is an important research area of nanofluids, which provides many opportunities to explore new frontiers but also poses great challenges. This paper presents a comprehensive review on the nanofluid heat transfer (HT) and critical heat flux (CHF) of pool boiling and flow boiling. The research results in the literature previously reviewed are briefly summarized. An emphasis is put on the recent progresses in the nanofluid HT and CHF of pool boiling and flow boiling. It is also included comparing developments and research results of the nanofluid HT and CHF between pool boiling and flow boiling. The important achievements, inconsistence, and contradictions of the existing research results are identified and discussed in detail. Topics worthy of attention for future studies are suggested. [ABSTRACT FROM AUTHOR]

• The absorption cross section of nitrogen dioxide changes with the change of temperature, which will affect the concentration inversion of nitrogen dioxide differential absorption lidar. • The temperature decreases with the increase of altitude, so the absorption cross section of nitrogen dioxide must be corrected in the concentration inversion. • It is generally considered that the temperature is constant in horizontal detection, but the temperature is different in different seasons or different times of the day, so the absorption cross section of nitrogen dioxide must be corrected. • Therefore, when using differential absorption lidar to detect the concentration of nitrogen dioxide in the atmosphere, whether it is horizontal or vertical detection, the absorption cross section must be corrected. A differential absorption lidar (DIAL) for measurement of atmospheric nitrogen dioxide (NO 2) concentration is developed based on atmospheric backscattered signals. Two Nd:YAG lasers are used to pump into two dye lasers to produce two wavelengths λon (448.1 nm) and λoff (446.6 nm), respectively. The NO 2 absorption cross section varies with the change of ambient temperature. The changes of NO 2 absorption cross section and the influence of inversion concentration are analyzed. The results show that when the horizontal profile is measured with the absorption cross section at room temperature of 20 °C as the reference value, the relative error of 1% can be caused by the temperature change of 1 °C. In vertical profile measurement, on the ground below 3 km, every 100 m increase in altitude can bring a relative error of 0.6%. By correcting the absorption cross section affected by temperature, the relative error of the measured concentration is less than 5%.On this basis, the experimental observation of atmospheric NO 2 concentration profiles was carried out, and errors induced by temperature change were corrected. The experimental results show that the system is stable and reliable, and the temperature correction algorithm is effective. [ABSTRACT FROM AUTHOR]

Developing high-efficiency hydrogen evolution reaction (HER) catalysts is of great interest for the large-scale high-purity hydrogen production, which, unfortunately, is largely blocked by the sluggish kinetics of the electro-chemical dissociation step of water molecules. Herein, a MOF-derived method has been developed to prepare Ru nanoparticles-anchored sponge-like WNO embedded in N-doped carbon layers (Ru@WNO-C). The fabricated catalyst Ru@WNO-C (Ru: 0.9 wt%) shows excellent HER catalytic activity and long-term stability with the overpotentials of 172, 358 and 24 mV at 10 mA/cm2 in 0.5 M H 2 SO 4 , 1 M Na 2 SO 4 and 1 M KOH, respectively. More impressively, the overpotentials, especially in neutral medium, decrease markedly during the durability tests owing to the catalyst structure activation after residual Zn species leaching. The enhanced catalytic activity of Ru@WNO-C during operation is mainly attributed to the in-situ electron donation from Ru to W, leading to the easier cleavage of highly polarized H‒OH bond of water molecules and thus endowing Ru@WNO-C with excellent HER catalytic performance in non-acidic solution. Ru nanoparticles-anchored WNO nano-sponges possess excellent HER catalytic performance under all-pH conditions (especially in neutral) due to the electron donation from Ru to W, and this electron donation effect is strengthened during operation leading to the significant enhancement of HER performance. ga1 • A novel porous-structured Ru@WNO-C sponge (Ru = 0.9 wt%) has been fabricated by a "MOF-derived method". • The Ru@WNO-C demonstrates excellent HER catalytic activity and stability in all-pH values. • The in-situ electron donation effect has been identified to be responsible for the superior HER performance. • Significant activity enhancement has been achieved during cyclic test by the strengthened electron donation effect. [ABSTRACT FROM AUTHOR]

The saturated flow boiling heat transfer of nitrogen (N 2 ) in a vertical upward 11.9 mm inner diameter stainless steel tube was experimentally investigated. The heat transfer coefficient (HTC) was measured as a function of vapor quality. Totally 414 experimental data points were obtained, with the parameter range of vapor quality from 0.01 to 0.99, pressure from 0.84 to 2.29 MPa, heat flux from 9 to 98.8 kW/m 2 , and mass flux from 110 to 800 kg/m 2 s. The effects of vapor quality, heat flux, mass flux, and pressure on the HTC are explored. Four flow patterns are identified by analyzing the HTC data, including bubbly flow, annular flow with liquid in the core and vapor between the liquid and the tube wall, dispersed flow, and mist flow. The trend of the HTC along the tube length (with vapor quality) is explained in relation to flow patterns. The flow and heat transfer characteristics in the experiments are compared with those in horizontal macro-tubes. Substantial differences between these two flow directions are revealed. For upward flow in vertical macro-tubes, it is fairly commonly seen that there are two occurrences of critical heat flux (CHF) along a uniformly heated channel. The mechanisms resulting in this phenomenon are found. The experimental data are compared with the correlations of saturated flow boiling heat transfer coefficient. The best one has a mean absolute deviation of 16.6%. [ABSTRACT FROM AUTHOR]

• Dual-functional hierarchical mechanical metamaterials are proposed for simultaneous vibration insulation and energy absorption. • The effects of the hierarchical configurations on the band gap distributions and energy absorption efficiency are systematically studied. • The parameter analysis is performed to analyze the effects of structural parameters on the band gap characteristics and crushing performance. • The multi-objective optimization is employed to seek the optimal structural design. In this study, the vibration isolation characteristics and crushing behaviors of novel hierarchical mechanical metamaterials are investigated. Numerical analyses are carried out for a class of mechanical metamaterials with different hierarchical configurations. The effects of the hierarchical configurations on the band gap distributions and energy absorption efficiency are carefully studied. The results indicate that the hierarchical configuration has remarkable potential in broadening the band gap and improving energy-absorbing efficiency. Moreover, the configuration (S3) with the best performance of vibration isolation and energy absorption among the proposed metamaterials is determined. The parameter analysis on S3 is further performed to analyze the effects of structural parameters on the band gap characteristics and crushing performance. Finally, multi-objective optimization is employed to seek optimal structural parameters of S3 for enhancing the gap-midgap ratio and the specific energy absorption, simultaneously. This study provides effective guidance for designing mechanical metamaterials with excellent vibration isolation capacity and energy absorption efficiency. [ABSTRACT FROM AUTHOR]

Finding efficient and versatile catalysts that can both produce clean energy H 2 and treat wastewater is an important matter to solve energy shortages and wastewater pollution. Herein, a feather-like NiCoP supported on NF was synthesized via the two-step hydrothermal-phosphorization process. NiCoP/NF requires only overpotentials of 44 and 203 mV to reach 10 mA cm−2 for HER and OER in 1 M KOH, respectively. Besides, NiCoP/NF requires only 1.13 V (vs RHE) to achieve 10 mA cm−2 in 1 M KOH containing 0.33 M urea. DFT calculation shows that NiCoP exhibits enhanced DOS in the Fermi level attachment, which promotes charge transfer. Subsequently, the trifunctional NiCoP/NF, for overall water splitting, requires a lower potential of 1.48 V to gain 10 mA cm−2 in 1 M KOH. For urea electrolysis, NiCoP/NF requires just 1.36 V to drive 10 mA cm−2 in 1 M KOH with 0.33 M urea. This work provides extraordinary insights into electrolytic hydrogen production and wastewater treatment through simple preparative methods. The performance of the prepared catalyst is at a high level in non-noble metal. [ABSTRACT FROM AUTHOR]

Experiments on R1234yf flow boiling in a horizontal 2.01 mm copper tube under hypergravity are conducted to investigate the effect of gravity on two-phase flow boiling heat transfer coefficient (HTC). The experimental range of parameters is gravity levels of 1–3.16 g, mass fluxes of 365 and 570 kg m−2 s−1, saturation pressures of 0.62 and 0.70 MPa, heat fluxes of 47.6 and 97.5 kW m−2, and vapor qualities up to 0.985. Based on the experimental data, the effects of gravity, quality, heat flux, mass flux, and saturation pressure on the HTCs were analyzed. The results show that the HTCs increase with increasing gravity levels for the qualities up to around 0.7, and the gravity effects become indistinct and inconsistent when the quality is high (x > 0.8). The trends of the HTC variation with quality and the effects of the heat flux , mass flux and saturation pressure on the HTCs are similar under different gravity levels. When x < 0.6, the nucleate flow boiling mechanism dominates with the HTCs varying little with quality, and the HTCs increase significantly with increasing heat flux and negligibly with increasing mass flux and pressure. The critical heat fluxes occur when x > 0.7 or higher, and they occur earlier when the gravity level is higher. The comparison of the experimental data with existing saturated flow boiling HTCs for normal gravity shows that the Fang (2013b) correlation for R134a performs best with a mean absolute deviation (MAD), and that all of the top four correlations in prediction accuracy under-predict the experimental HTCs, which is consistent with the experimental results that hypergravity enhances flow boiling heat transfer. [ABSTRACT FROM AUTHOR]

Vibrations propagating underground may have harmful effects on adjacent buildings and human health. Recently, the notion of phononic crystals has been introduced and applied to isolate vibrations below the ground. In this paper, considering the viscoelastic material model, the complex band diagrams are suggested to analyse the transportation of vibrations in the composite foundation consist of soil and different underground structures. In the complex band diagram, the minimum imaginary part of the wave vectors is taken as the index to measure the ability of the pile group to weaken vibrations. Several types of underground barriers, including circular piles, continuous walls, and multi-layer piles, are analysed. The result shows that multi-layer piles can induce local resonance and achieve an attenuation zone at the low-frequency level. The attenuation effect of periodic barriers is then verified by transmission models. The results show that the complex band diagrams can quantitatively evaluate the isolation effect of periodic barriers, which is beyond the capability of classic band diagrams. [ABSTRACT FROM AUTHOR]

• We propose a physical model-driven untrained deep convolutional autoencoder network for SPI and validate its performance from simulations and experiments. • We designed an end-to-end SPI reconstruction network, which can better reconstruct high-quality images from under-sampled measurements. • We perform a comparative study through the simulations and experiments. The results demonstrate that UCAN outperforms other existed SPI methods, including DGI, TVAL3, and GIDC. Single-pixel imaging (SPI) is a novel imaging modality which captures the images with a single-pixel detector by using a lot of time-varying modulation patterns. Nowadays, SPI reconstructions with data-driven deep learning had been verified for high-quality reconstructions under low sampling ratios. However, it faces a dilemma of hard-to-get sufficient training sets in many practical applications, e.g., long-range single-pixel imaging fields. Here, a model-driven SPI reconstruction method based on untrained convolutional autoencoder network (UCAN) is proposed. This framework does not need to pre-train on any dataset and can be automatically optimized, then eventually produce the restored images through the interplay between the neural network and the SPI physical model. Simulations confirm the superiorities of the proposed method over many other existed algorithms in the SPI field. Also, the reconstructions for long-range single-pixel imaging in real urban atmospheric environments demonstrate that our method has better denoising performance. We believe that the present work provides an alternative framework for SPI and paves the way for practical applications, e.g., long-range optical remote sensing and low-irradiative biological imaging. [ABSTRACT FROM AUTHOR]

• A novel three-dimensional lattice metamaterials with great vibration isolation performance and crashworthiness is proposed. • The band gap characteristics of the three-dimensional lattice metamaterial can be flexibly adjusted. • The deformation modes and energy absorption efficiency of the three-dimensional lattice metamaterial are investigated. • A multi-objective optimization design for the three-dimensional lattice metamaterial is conducted. This work investigates the vibration isolation performance and crashworthiness of a novel three-dimensional (3D) lattice metamaterial, whose unit cell is constructed by combining a hollow rhombic dodecahedron and six cylindrical tubes. The transmission of elastic waves in the 3D metamaterial can be suppressed for the existence of band gaps in the metamaterial. Meanwhile, the 3D metamaterial can absorb the crushing energy through plastic deformation when a collision occurs. The influence of structural parameters on the band gap features and crashing behaviors of the novel 3D metamaterial are examined. It is shown that the structural parameters play a vital role in determining the band gap features and crashing behaviors. Thus, the required vibration isolation performance and crashworthiness can be obtained by adjusting the structural parameters reasonably. Finally, multi-objective optimization is performed from the comprehensive aspects of vibration isolation performance and crashworthiness to obtain the optimal design of the novel 3D metamaterial. This work provides a new possibility for the development of multifunctional metamaterials with vibration isolation performance and crashworthiness simultaneously. [ABSTRACT FROM AUTHOR]

• A mechanical lattice model of second-order elastic topological insulator is established to predict edge and corner states. • The corner states can be selectively activated by engineering the positions of the valley. • An extra type of corner states with anti-symmetric polarization is firstly observed in either acoustic or elastic system. • The topological corner states are tested robust enough against the disorders. Second-order elastic topological insulators (SETIs) with topologically protected corner states offer new routes for the realization of the robust manipulation of elastic waves in lower dimensions, providing the unprecedented ways for integrated ultrasound sensors and energy harvesting devices. However, traditional SETIs lack the flexibility of turning on and off the corner states on demand. Herein, we proposed a type of SETIs possessing the valley-selective topological corner states, endowing the capability of activating corner states by engineering the valley positions. An extra type of corner states with anti-symmetric displacement profile is also observed in the proposed SETIs, which is attributed to the enhanced long-range effect. The discrete mechanical model is firstly investigated and then expanded into the PC plate, in which the theory of Wannier center can well elucidate the corner states with valley-selectivity. The experimental results validate the existing corner states with valley-selectivity and anti-symmetric displacement profile. The proposed discrete model acts as a versatile platform presenting the relevant topological effects. The achieved valley-selectivity and multi-polarization features hosted in the designed SETI may contribute to their practicality and reconfigurability in elastic energy trapping, detecting, and harvesting device. [Display omitted] [ABSTRACT FROM AUTHOR]

• A thermal expansion model of tooth profile under the steady bulk temperature field is established. • An analytical method for calculating mesh stiffness of spur gear considering thermal effect is proposed. • The proposed models are verified by the finite element method. • The effects of temperature on mesh stiffness, load sharing ratio and loaded static transmission error are analyzed. • The difference between uniform and non-uniform temperature field on mesh stiffness are discussed. Thermal effect is an important cause of engineering failure of gear system. However, the lack of accurate model limits the research on the thermal behavior of gear transmission system. Here, based on the linear thermal expansion theory, involute profile theory and energy method, the thermal expansion model, the mesh stiffness model, the load sharing ratio model and the loaded static transmission error model of spur gears are proposed which comprehensively consider the thermal changes of material properties, theoretical involute, thermal profile error and actual contact positions. The corresponding finite element models are established to verify the accuracy of the proposed model and published models. The results indicate that the proposed model is accurate enough. The increase of temperature leads to the decrease of mesh stiffness, the unevenness of load sharing ratio and the increase of loaded static transmission error, accompanied by the phenomenon of earlier meshing. The hub bore radius has obvious influences on the thermal profile error and mesh stiffness, and the load torque also has apparent influences on mesh stiffness. The research provides supports for gear thermal effect analysis and gear system design. [ABSTRACT FROM AUTHOR]