Multidimensional Vibrations of Cable-Harnessed Beam Structures with Periodic Pattern: Modeling and Experiment

The dynamics of space structures is significantly impacted by the presence of power and electronic cables. Robust physical model is essential to investigate how the host structure dynamics is influenced by cable harnessing. All the developed models only considered the decoupled bending motion. Initial studies by authors point out the importance of coordinate coupling in structures with straight longitudinal cable patterns. In this article, an experimentally validated mathematical model is developed to analyze the fully coupled dynamics of beam with a more complex cable wrapping pattern which is periodic in nature. The effects of cable wrapping pattern and geometry on the system dynamics are investigated through the proposed coupled model. Homogenization-based mathematical modeling is developed to obtain an analogous solid beam that represents the cable wrapped system. The energy expressions obtained for fundamental repeating segment are transferred into the global coordinates consisting of several periodic elements. The coupled partial differential equations (PDE) are obtained for an analogous solid structure. The advantage of the proposed analytical model over the existing models to analyze the vibratory motion of beam with complex cable wrapping pattern has been shown through experimental validation.

Epidemiological characteristics of Epstein–Barr virus infection

Introduction. The Epstein–Barr virus (EBV) is one of the most common pathogens — it infects 90% of the world’s population. However, specific characteristics of the EBV infection epidemic process remain unidentified. The previous studies focusing on assessment of incidence rates for infectious mononucleosis (IM) tend to ignore the serological status of the population.The aim of the study was to identify epidemiological characteristics and assess the prevalence of serological markers for EBV infection for further epidemic control measures development.Materials and methods. In Moscow, the thorough analysis was performed using the data on IM incidence (Form 2 "Data on Infectious and Parasitic Diseases") and test results for 138,232 people checked for presence of VCA IgG, EBNA IgG, VCA IgM, EA IgG, and EBV DNA in their blood and saliva in 2011–2020.Results. The periodic pattern of IM incidence was discovered, demonstrating the repetitive peaks every 9 to 11 years and a strong direct correlative relationship with detection rates for active EBV infection markers. The intra-annual dynamics of IM incidence is characterized by a seasonal upswing during cold seasons of the year, reaching its peaks in October, November, or February and associated with a marked decrease in the VCA IgG and EBNA IgG seroprevalence. Children within the 1 to 17-year age range are groups at risk for acquiring primary infection, demonstrating significantly lower detection rates for chronic EBV infection (VCA IgG and EBNA IgG) markers and higher rates for VCA IgM and EBV DNA markers in blood compared to adults. The contribution of adult population to the epidemic process is formed through reactivation of chronic infection, which is observed primarily among women.Conclusion. The identified characteristics are essential for comprehensive understanding of the EBV infection epidemic process and can be used for developing preventive and anti-epidemic measures.

Spatial variation of geometry, binding, and electronic properties in the moiré superstructure of MoS2 on Au(111)

The lattice mismatch between a monolayer of MoS2 and its Au(111) substrate induces a moiré superstructure. The local variation of the registry between sulfur and gold atoms at the interface leads to a periodic pattern of strongly and weakly interacting regions. In consequence, also the electronic bands show a spatial variation. We use scanning tunneling microscopy and spectroscopy (STM/STS), x-ray photoelectron spectroscopy (XPS) and x-ray standing wave (XSW) for a determination of the geometric and electronic structure. The experimental results are corroborated by density functional theory (DFT). We obtain the geometric structure of the supercell with high precision, identify the fraction of interfacial atoms that are strongly interacting with the substrate, and analyze the variation of the electronic structure in dependence of the location within the moiré unit cell and the nature of the band.

Periodic Pattern Detection of Printed Fabric Based on Deep Learning Algorithm

Printed fabric patterns contain multiple repeat pattern primitives, which have a significant impact on fabric pattern design in the textile industry. The pattern primitive is often composed of multiple elements, such as color, form, and texture structure. Therefore, the more pattern elements it contains, the more complex the primitive is. In order to segment fabric primitives, this paper proposes a novel convolutional neural network (CNN) method with spatial pyramid pooling module as a feature extractor, which enables to learn the pattern feature information and determine whether the printed fabric has periodic pattern primitives. Furthermore, by choosing pair of activation peaks in a filter, a set of displacement vectors can be calculated. The activation peaks that are most accordant with the optimum displacement vector contribute to pick out the final size of primitives. The results show that the method with the powerful feature extraction capabilities of the CNN can segment the periodic pattern primitives of complex printed fabrics. Compared with the traditional algorithm, the proposed method has higher segmentation accuracy and adaptability.

Topology optimization of periodically arranged components using shared design domains

Building structures from identical components organized in a periodic pattern is a common design strategy to reduce design effort, structural complexity and cost. However, any periodic pattern will impose certain design restrictions often leading to lower structural efficiency and heavier weight. Much research is available for periodic structures with connected components. This paper addresses minimal compliance design for periodic arrangements of unconnected components. The design problem discussed here is relevant for many applications where a tightly nested, space-saving arrangement of identical components is required. We formulate an optimal design problem for a component being part of a periodic arrangement. The orientation and position of the component relatively to its neighbours are prescribed. The component design is computed by topology optimization on a design domain possibly shared by several neighbouring components. Additional constraints prevent components from overlapping. Constraint aggregation is employed to reduce the computational cost of many local constraints. The effectiveness of the method is demonstrated by a series of 2D and 3D examples with an ever-smaller distance between the components. Moreover, problem-specific ranges with only little to no increase in compliance are reported.

Fabrication of Large Area, Ordered Nanoporous Structures on Various Substrates for Potential Electro-Optic Applications

Nanoporous structures have attracted great attention in electronics, sensor and storage devices, and photonics because of their large surface area, large volume to surface ratio, and potential for high-sensitivity sensor applications. Normally, electron or ion beam patterning can be used for nanopores fabrication by direct writing. However, direct writing is a rather expensive and time-consuming method due to its serial nature. Therefore, it may not translate to a preferred manufacturing process. In this research, a perfectly ordered large-area periodic pattern in an area of approximately 1 cm2 has been successfully fabricated on various substrates including glass, silicon, and polydimethylsiloxane, using a two-step process comprising visible light-based multibeam interference lithography and subsequent pattern transfer processes of reactive ion etching and nanomolding. Additionally, the multibeam interference lithography templated anodized aluminum oxide process has been described. Since the fabrication area in multibeam interference lithography can be extended by using a larger beam size, it is highly cost effective and manufacturable. Furthermore, although not described here, an electrodeposition process can be utilized as a pattern transfer process. This large-area perfectly ordered nanopore array will be very useful for high-density electronic memory and photonic bandgap and metamaterial applications.

Fully-printed metamaterial-type flexible wings with controllable flight characteristics

Insect wings are an outstanding example of how a proper interplay of rigid and flexible materials enables an intricate flapping flight accompanied by sound. The understanding of the aerodynamics and acoustics of insect wings have enabled the development of man-made flying robotic vehicles and explained basic mechanisms of sound generation by natural flyers. This work proposes the concept of artificial wings with a periodic pattern, inspired by metamaterials, and explores how the pattern geometry can be used to control the aerodynamic and acoustic characteristics of the wing. For this, we analyzed bio-inspired wings with anisotropic honeycomb patterns flapping at a low frequency and developed a multi-parameter optimization procedure to tune the pattern design in order to increase lift and, simultaneously, manipulate the produced sound. Our analysis is based on the finite-element solution to a transient three-dimensional fluid-structure interactions problem. The two-way coupling is described by incompressible Navier-Stokes equations for viscous air and structural equations of motion for a wing undergoing large deformations. We manufactured three wing samples by means of 3D printing and validated their robustness and dynamics experimentally. Importantly, we showed that the proposed wings can sustain long-term resonance excitation that opens a possibility to implement resonance-type flights inherent to certain natural flyers. Our results confirm the feasibility of the metamaterial patterns to control the flapping flight dynamics and can open new perspectives for applications of 3D-printed patterned wings, e.g., in the design of drones with the target sound.

Impact of Pre-Patterned Structures on Features of Laser-Induced Periodic Surface Structures

The efficiency of light coupling to surface plasmon polariton (SPP) represents a very important issue in plasmonics and laser fabrication of topographies in various solids. To illustrate the role of pre-patterned surfaces and impact of laser polarisation in the excitation of electromagnetic modes and periodic pattern formation, Nickel surfaces are irradiated with femtosecond laser pulses of polarisation perpendicular or parallel to the orientation of the pre-pattern ridges. Experimental results indicate that for polarisation parallel to the ridges, laser induced periodic surface structures (LIPSS) are formed perpendicularly to the pre-pattern with a frequency that is independent of the distance between the ridges and periodicities close to the wavelength of the excited SPP. By contrast, for polarisation perpendicular to the pre-pattern, the periodicities of the LIPSS are closely correlated to the distance between the ridges for pre-pattern distance larger than the laser wavelength. The experimental observations are interpreted through a multi-scale physical model in which the impact of the interference of the electromagnetic modes is revealed.

The overlapped latent fingerprint separation by using Fourier Optics (FO)

Latent fingerprints are one of the most important pieces of evidence left at a crime scene and can be linked to all individuals involved. Each person’s fingerprints are unique and permanent, becoming an ideal biometric trait for the personal identification by extracting and comparing characteristic points (minutiae) of ridges. The overlapping fingerprint cases are frequently encountered in a crime scene and causing a difficult interpretation for an investigator. The problem has been challenging for forensic scientists over a decade. The method proposed in this study for the separation of overlapped latent fingerprints is based on the well-known spatial filtering method in the Fourier Optics (FO). Instead of tackling the problem by experiment, an alternative and simple means of image processing was proposed and conducted. The working principles start form converting spatial domain patterns (an image of overlapped fingerprints) to spatial frequency domain patterns or power spectrum, filtering out unwanted components (unwanted fingerprint) by appropriate spatial filters, and finally converting the modified pattern back to spatial domain patterns (an image of suspect fingerprint). As a result, the final image is improved from its original state. The periodic pattern of ridges is the key that allows FO to be used in the separation of the overlapped fingerprints. In this work, the procedures described are simply performed by an open source software: ImageJ. The FO-based image processing technique satisfactorily demonstrated its ability to recover an individual fingerprint from overlapping fingerprints.