As blockchain technology advances, non-fungible tokens (NFTs) are emerging as unconventional assets in the commercial market. However, it is necessary to establish a comprehensive NFT ecosystem that addresses the prevailing public concerns. This study aimed to bridge this gap by analyzing user-generated content on prominent social media platforms such as Twitter, Weibo, and Reddit. Employing text clustering and topic modeling techniques, such as Latent Dirichlet Allocation, we constructed an analytical framework to delve into the intricacies of the NFT ecosystem. Our investigation revealed seven distinct topics from Twitter and Reddit data and eight topics from Weibo data. Weibo users predominantly engaged in reviews and critiques, whereas Twitter and Reddit users emphasized personal experiences and perceptions. The NFT ecosystem encompasses several crucial elements, including transactions, customers, infrastructure, products, environments, and perceptions. By identifying the prevailing trends and common issues, this study offers valuable guidance for the development of NFT ecosystems.

Passivation layers can significantly affect the mechanical behavior of microscale materials due to their blocking effect on dislocations. Previous studies employed microscopically hard boundary conditions to describe passivated surfaces, assuming plastic strain is zero at the surface, which may lead to an overprediction of the passivation effect. This paper proposed a two-layer model for the passivated wire torsion based on the strain gradient plasticity theory, where the passivation layer is considered as an additional layer outside the substrate. The torsion test results of the passivated Cu wires with different passivation layer thicknesses and materials demonstrated that passivation material parameters significantly affect the torsional response of wires. The applicability of the two-layer model was verified by comparing it with the single-layer model (considering the passivation layer as boundary conditions) and experiment data. Simulations showed the yield strength of the passivation materials determines the failure time of the blocking effect on dislocations and therefore becomes the dominant material parameter for the passivation effect.

Digital image correlation methods are used to obtain the deformation parameters by matching the target image with the reference image. The analysis accuracy of the deformation parameters is affected by several factors, among which the reconstruction algorithm of the target image is one of the main influencing factors. In this study, a target image reconstruction algorithm based on Taylor series interpolation is proposed to improve the calculation accuracy of deformation parameters. According to the theory of Fourier transform, the general relationship between the image gray value gradient and the image Fourier transform is deduced, which lays the foundation for Taylor series interpolation to be applied to the reconstruction of target image. Since the global derivatives of the image are pre-calculated based on the fast Fourier transform algorithm, and the derivatives used for Hessian matrix and Taylor series interpolation of the image sub-regions can be read directly from the overall derivatives in the subsequent iterations, this algorithm is characterized by high computational efficiency. Considering the computational accuracy and efficiency, this paper adopts the fourth-order Taylor series expansion as the interpolation algorithm for target image reconstruction. In order to evaluate the displacement analysis accuracy of the proposed algorithm in this paper, the displacement analysis results of the Taylor series interpolation algorithm are compared with the computational results of the bicubic B-spline interpolation and biquintic B-spline interpolation algorithms, respectively. The analysis of the results shows that the proposed algorithm is superior to the above two algorithms in terms of displacement analysis accuracy and computational efficiency. In addition, the results of the displacement field analysis of the proposed algorithm in actual tensile experiments with a hole are also shown in the paper.

Cyclic torsion tests are performed on micron-scale copper wires with and without surface passivation to study the role of the higher-order condition in the plastic behavior of thin wires under non-proportional loading. A typical strengthening size effect is observed in the symmetric cycles. More obvious strength enhancement exists in the torsional response of passivated copper wires. An unusual Bauschinger effect is found during the loading-unloading cycles, which is more pronounced in passivated wires. The finite element implementation based on Gudmundson’s strain gradient plasticity theory is developed for wire torsion to characterize the observed size-dependent phenomena. The higher-order boundary conditions are introduced to simulate the passivated surface. The predicted radial distributions of plastic strain, stress components, and geometrically necessary dislocation density for the passivated and unpassivated wires are given and compared. This work provides a reasonable basis for understanding the role of higher-order conditions of strain gradient plasticity.

In this paper, we introduce an accelerating algorithm based on the Taylor series for reconstructing target images in the spectral digital image correlation method (SDIC). The Taylor series image reconstruction method is employed instead of the previous direct Fourier transform (DFT) image reconstruction method, which consumes the majority of the computational time for target image reconstruction. The partial derivatives in the Taylor series are computed using the fast Fourier transform (FFT) of the entire image, following the principles of Fourier transform theory. To examine the impact of different orders of Taylor series expansion on accuracy and efficiency, we employ third- and fourth-order Taylor series image reconstruction methods and compare them with the DFT image reconstruction method through simulated experiments. As a result of these enhancements, the computational efficiency using the third- and fourth-order Taylor series improves by factors of 57 and 46, respectively, compared to the previous method. In terms of analysis accuracy, within a strain range of 0–0.1 and without the addition of image noise, the accuracy of the proposed method increases with higher expansion orders, surpassing that of the DFT image reconstruction method when the fourth order is utilized. However, when different levels of Gaussian noise are applied to simulated images individually, the accuracy of the third- or fourth-order Taylor series expansion method is superior to that of the DFT reconstruction method. Finally, we present the analyzed experimental results of a silicone rubber plate specimen with bilateral cracks under uniaxial tension.

Soft filaments can be stretched, bent, and twisted, exhibiting complex configurations. When a filament undergoes large torsional deformation, it can display instabilities, and its post-buckling behavior and configuration evolution differs significantly from that observed under small deformation. We study the mechanics and topologically complex morphologies of twisted rubber filaments under prescribed elongation by combining experiment and finite strain theory. Based on the Mooney-Rivlin model, a finite strain theory of the hyperelastic filament under combined tension, bending, and torsion has been established, accounting for both geometrical and material nonlinearities. An experimental and theoretical morphological phase diagram is constructed as a function of the twist density and the initial elongation. The buckling and post-buckling behaviors of the twisted rubber filaments under prescribed elongation are well captured by the theory that considers geometrical nonlinearity and self-contact. By tracking the interconversion of link, twist, and writhe, we accurately determine the configuration and the critical points of phase transitions. The theoretical predictions agree closely with the measurements. This work sheds light on understanding the morphological complexity of the loaded hyperelastic rod.

A micro-force measuring system with a resolution of micro-Newton based on the principle of torsion balance is developed, which consists of micro-force sensor, linear motor, specimen platform and the matching measurement and control software based on LabVIEW. The dynamic method of calibrating the micro-force sensor by in-situ vibration was used to overcome the influence of boundary conditions such as the rod and the clamp, achieving an accurate calibration of the torsional constant. The system was applied to study the process of pressing a slender cylinder imitating the leg of a water strider into the water surface. The results show that the critical interaction force per unit volume of the slender cylinder decreases with the increase of its diameter, showing a significant size effect; the critical depth and critical interaction force can be increased by spraying superhydrophobic silica coating, which greatly improves the hydrophobic performance of the slender cylinder.

A spectral image correlation method considering the effect of displacement gradients upon displacement analysis in the Fourier frequency domain is proposed. A spectral image correlation criterion is studied and established to match the target subset image with the reference subset image in the frequency domain. An iterative algorithm for calculating displacement and strain is then derived, and the Hessian matrix remains unchanged within an iterative process. During the formation of the Hessian matrix, the greyscale gradients of the reference subset image can be calculated using the fast Fourier transform with high computational efficiency and accuracy. An accurate Fourier transform resampling technique, instead of the traditional interpolation method, is used to reconstruct or up-date the target image at a subpixel position in the deformed subset image. To verify the validity and accuracy of the proposed method, a series of images (2D-Challenge 1.0, sample 6) provided by the International DIC Challenge Committee (IDCC) was used for displacement analysis. The analyzed error results show that the proposed method is better than the published literature in accuracy. The second simulation experimental result with a strain of 50% is performed and the corresponding displacement accuracy is about 0.0032 pixel under the condition of 41 × 41 subset. Finally, a 14.85% uniaxial tensile test of a silicone rubber specimen is performed, and the analyzed displacement and strain distribution are given.

Slender structures, from DNA and proteins to ropes and strings, are widely seen in nature and industry. Soft filaments could undergo stretch, bend and twist deformations, thus enabling complex configuration transitions, including solenoid and plectoneme. The instabilities of twisted filaments under different pulling forces are studied based on the Cosserat rod theory. The connections between geometrical transformation and mechanics are clarified by considering geometric nonlinearities and self-contact. The interconversions of link, twist, and writhe in the complex structures of twisted filaments are discussed. Experiments on the instabilities of nylon 6 filaments under torsion and stretch are performed simultaneously. The theoretical predictions are in reasonable agreement with the experiments. This study sheds light on understanding the formation mechanism of the twisted-and-coiled polymer muscles.

The combination resonance of size-dependent microbeams is investigated. Two harmonic forces act on the microbeam, and combination resonance is observed while the excitation frequencies differ from the resonant frequency. Microbeams with two different sources of nonlinearities including three kinds of boundary conditions, clamped-free (nonlinearity comes from large curvature and nonlinear inertial), clamped-clamped, and hinged-hinged (nonlinearity originates from mid-plane stretching-bending coupling), are taken into consideration to have a deep understanding of this phenomenon. A traveling load acting on the microbeam is presented as a special case of combination resonance. The modal discretization technique is applied to discretize the equations of motion, and then the Lindstedt–Poincare method, a perturbation approach, is employed to solve the resultant equations. The conditions for combination resonance are presented, and frequency-response curves and time histories at the resonance point are obtained for microbeams of each boundary condition. Results reveal that different sources of nonlinearities result in different performances of combination resonance. The free vibration part constitutes a large percentage of the final response. Furthermore, the situation of coexistence of combination resonance and superharmonic (or subharmonic) resonance is determined. The special case demonstrates a higher amplitude than the common combination resonance for all the boundary conditions. Parametric studies are then carried out to discuss the effects of the length scale parameter, excitation force as well as its position, and damping on the performance of the microbeam.

Non-fungible tokens (NFTs) have gathered worldwide attention over the past several years. NFTs are cryptographic assets that use blockchain technology to represent ownership of digital goods and to store a digital asset’s ownership certificate (Kanellopoulos, Gutt, & Li, 2021). The non-fungible aspect of NFTs makes each token unique and can represent a specific object. These tokens are stored on a blockchain and can be used to merchandise digital assets in various forms (e.g., photos, videos, and audio). Furthermore, the creator of an NFT can earn royalties for each successful trade made on any NFT marketplace which is a website where one can create, sell, and buy NFTs. Due to the transparent and immutable properties provided by the blockchain, the entire historical record of ownership transactions becomes verifiable by each network participant, providing a promising intellectual property protection solution. NFTs were only known by blockchain amateurs at the beginning but have gathered mass attention and have their own market in recent years. People have expressed tremendous interest in various types of NFTs in different industries, such as gaming, arts, collectibles, and the metaverse. For example, CryptoPunks, one of the first NFTs, made one of the most significant digital art sales in history for nearly $24 million (Manoylov, 2022). CryptoKitties, a digital cat breeding game, had 1.5 million users responsible for $40 million worth of transactions on its platform (CryptoKitties Explained, 2021). Besides art and game, NFTs also promote the development of ticketing events, news, fashion, supply chain, and surrounding markets such as social portals (e.g., DappRadar), trading marketplace (e.g., OpenSea), and financial instruments (e.g., Defi) (Wang, Li, Wang, & Chen, 2021). Many leading global consumer brands such as Adidas, Coca-Cola and Nike have started to engage with their loyal fans using NFTs (Shanmugham, 2022). A report estimated that the overall value of the NFT market in 2021 is around $15.7 billion and would rise to $122 billion by 2028 (SkyQuest Technology Consulting Pvt, 2021). On the other hand, NFTs have their drawbacks. The generation and transaction of NFTs are highly energy-intensive and may negatively affect the environment over time. For instance, one NFT transaction costs as much electricity as the typical home for about a day (The Renewable Energy Hub, 2021). Also, NFTs are illiquid and speculative investments (Wilson, Karg, & Ghaderi, 2022). Since it is a new market asset, its value is unstable and is based on the price someone is willing to pay for it without much historical data for reference. NFTs can still be attacked and stolen by hackers, which face the risk of fraud and abuse (Wang, Li, Wang, & Chen, 2021). Moreover, owning an original NFT does not mean the owner can control its distribution or duplication. The owner cannot stop others from making and sharing “prints” (Rehman, E Zainab, Imran, & Bawany, 2021). So, how will the NFT market evolve in the coming years? Will it keep blooming or bursting? Although NFTs have a tremendous impact on the current decentralized markets, research on NFTs is still in a very early stage. This study aims to summarize the current status of the NFT market, discuss the potential challenges and promising opportunities related to NFT, and suggest some directions for further research.

In this paper, the systematic study of the analysis and measurement of displacement fields with large deformations based on an improved spectral digital image correlation (SDIC) method is conducted. As a shape function including displacement gradients has been successfully introduced, the SDIC method can deal with deformation issues involving different strains. We use the large image Fast Fourier Transform (FFT) to calculate full-field gray gradients instead of the subset image FFT. Therefore, all the gray gradients on image grids can be computed before formation of the Hessian matrix and the iterative optimization process. This can improve the efficiency and accuracy of the SDIC method. To analyze deformation with large strain, an easy-to-use and effective initial displacement estimation method for the seed point is introduced based on the correlation searching technique. The final displacements and displacement gradients of the region of interest (ROI) are then calculated by the subsequent iterative optimization algorithm, which can converge when the initial displacement error is within the range of +/- 3 pixels. A set of images with noise ranging from 0 to 4 standard deviations and strains ranging from 0 to 0.6 are simulated and analyzed. The error analysis confirmed that the improved SDIC method performs well in anti-noise and can accurately analyze the displacement field. Finally, the silicone rubber specimens were tested in compression, tension and bending and analyzed to further confirm the validity of the improved SDIC method in the measurement of large deformations.

Torsion tests are performed on microscale copper wires of diameters ranging from 25 to 50 μm, with and without passivation layers, to investigate the size and passivation effects. The copper wires coated with titanium are prepared by magnetron sputtering. An increase in the yield strength and flow stress arising from diameter reduction and the passivation layer is observed in the experiments. Compared with unpassivated wires, passivated wires exhibit more potent size effects. The normalized torque of passivated wires increases more significantly with the diameter decrease. The theoretical predictions based on the Fleck-Hutchinson strain gradient plasticity theory agree well with the experimental observations. The physical mechanism of the passivation layers affecting the torsional deformation of wires is elucidated.

The coupled effect of specimen size and grain size on the stress relaxation of micron-sized copper wires is investigated experimentally in this study. Both tension and repeated stress relaxation tests are performed on wires with the variation of diameters at annealing temperatures in the range of 300–800 °C. It is found that the yield strength is affected by the grain size and the ratio of the diameter (D) to the grain size (d) within the ratio below a critical value of 3. The classical Hall–Petch relation holds with the ratio of D/d larger than 3. Otherwise, a deviation from the relation arises. It is observed that the relaxation process is elevated as the specimen size and the grain size decrease. With the decrease of specimen size and grain size, the activation volume decreases. The coupled effect of specimen size and grain size in the activation volume is explained theoretically. The specimen size effect during the relaxation is related to the exhaustion mechanism that mobile dislocations annihilate at the free surface. More rapid exhaustion of mobile dislocations from the free surface arises in a smaller-diameter wire, thus accelerating the relaxation process. It is proposed that the deformation is dominated by the interaction of dislocations with grain boundaries within the grain size of less than about 6 μm. Within the ratio of D/d less than 3, the mechanism becomes the interaction of dislocations with forest dislocations.

A series of multi-scale sandwich cantilever micro-beams are prepared to investigate the size-dependent phenomenon in this paper. The sandwich micro-beam samples consist of a titanium substrate with a thickness of 1.996 mu m and two symmetrical nickel coatings with thickness between 106.6 and 362.6 nm by employing a physical vapor deposition method. The vibration responses of these composite micro-beams are excited by an acoustic exciter and measured by a laser Doppler vibration measurement system. It is revealed that with the decreasing of coating thickness, the dimensionless bending rigidity of nickel coating increases, and the dimensionless natural frequency of micro-beam increases first then decreases. Based on the non-classical continuum theories, the theoretical model of the sandwich micro-beam is established. Then the material length scale parameters are derived. The applicability of the non-classical continuum theories is verified when the material characteristic size of the structure is smaller than the material length scale parameter. The results are of great significance to the design and optimization of micro-/nano-electro mechanical systems.

Indium tin oxide (ITO) is widely used in a variety of optoelectronic devices, occupying a huge market share of $1.7 billion. However, traditional preparation methods such as magnetron sputtering limit the further development of ITO in terms of high preparation temperature (>350 °C) and low mobility (∼30 cm2 V-1 s-1). Herein, we develop an adjustable process to obtain high-mobility ITO with both appropriate conductivity and infrared transparency at room temperature by a reactive plasma deposition (RPD) system, which has many significant advantages including low-ion damage, low deposition temperature, large-area deposition, and high throughput. By optimizing the oxygen flow during the RPD process, ITO films with a high mobility of 62.1 cm2 V-1 s-1 and a high average transparency of 89.7% at 800-2500 nm are achieved. Furthermore, the deposited ITO films present a smooth surface with a small roughness of 0.3 nm. The stability of ITO films to heat, humidity, radiation, and alkali environments is also investigated with carrier mobility average changes of 19.3, 4.4, and 4.7%, showcasing strong environmental adaptability. We believe that stable ITO films with high mobility prepared by a low-damage deposition method will be widely used in full spectral optoelectronic applications, such as tandem solar cells, infrared photodetectors, light-emitting diodes, etc.

The COVID-19 pandemic has required many educators to offer online courses. Given the evidence of the effectiveness of the Process-Oriented Guided Inquiry Learning (POGIL), many educators are interested in implementing POGIL in online environments. This paper first discusses the challenges of using the POGIL approach to teach courses. Then we share our experience and our proposed approach (GICL) for teaching cybersecurity topics via the Zoom platform in the online environment. Recommendations for overcoming some of these challenges for online teaching are provided.

Slender ribbons can be stretched, bent, and twisted, exhibiting a range of complex morphologies. We study the morphology transitions of a ribbon subjected to tension and torsion by combining experiment and theory. A unified phase diagram as a function of torque and aspect ratio is constructed by comparing the microscopic and macroscopic buckling. Two distinct types of shape evolutions are identified. For the twist of a wide ribbon, the shape transforms from a helicoid through a crease to a cylinder. However, for a narrow ribbon under torsion, no crease occurs. The mechanical behavior of the stretched and twisted ribbon is described based on an energy method. It is found that the succession of transformations for the morphologies strongly depends on the aspect ratio and tension. This study sheds light on understanding the morphological complexity of a constrained slender structure.

Infrared solar cells are regarded as candidates for expanding the solar spectrum of c-Si cells, and the window electrodes are usually transparent conductive oxide (TCO) such as widely used indium tin oxide material. However, due to the low transmittance of the TCO in the near-infrared region, most near-infrared light cannot penetrate the electrode and be absorbed by the active layer. Here, the propose a simple procedure to fabricate the window materials with high near-infrared transmittance and high electrical conductivity, namely the hydrogen-doped indium oxide (IHO) films prepared by room temperature magnetron sputtering. The low-temperature annealed IHO conductive electrodes exhibit high mobility of 98 cm(2) V-1 s(-1) and high infrared transmittance of 85.2% at 1300 nm, which endows the lead quantum dot infrared solar cell with an improved short-circuit current density of 37.2 mA cm(-2) and external quantum efficiency of 70.22% at 1280 nm. The proposed preparation process is simple and compatible with existing production lines, which gifts the IHO transparent conductive film great potential in broad applications that simultaneously require high infrared transmittance and high conductivity.