Periodic Structures Research Articles

Symmetry Breaking as a Basis for Characterization of Dielectric Materials

This paper introduces a novel method for measuring the dielectric permittivity of materials within the microwave and millimeter wave frequency ranges. The proposed approach, classified as a guided wave transmission system, employs a periodic transmission line structure characterized by mirror/glide symmetry. The dielectric permittivity is deduced by measuring the transmission properties of such structure when presence of the dielectric material breaks the inherent symmetry of the structure and consequently introduce a stopband in propagation characteristic. To explore the influence of symmetry breaking on propagation properties, an analytical dispersion equation, for both symmetries, is formulated using the Rigorous Coupled Wave Analysis (RCWA) combined with the matrix transverse resonance condition. Based on the analytical equation, an optimization procedure and linearized model for a sensing structure is obtained, specifically for X-band characterization of FR4 substrates. The theoretical results of the model are validated with full wave simulations and experimentally.

Inhomogeneous MHz-scale intensity noise in double-pass fiber amplifiers

Abstract Here we report about the first demonstration of periodic MHz-scale inhomogeneous relative intensity noise (RIN) induced in double-pass fiber amplifiers. An Er:Yb-doped double-pass fiber amplifier operating near 1570.2 nm and stable continuous-wave single-frequency radiation source are used for the demonstration. The periodic structure of RIN has typical period of units of MHz observed in the range of 0–50 MHz and is formed in the radio-frequency spectrum of the amplified signal. It was found that the key factor influencing period of the RIN structure is spacing between the active fiber and a reflector forming the double-pass amplifier configuration. The population dynamics gratings formed in the active fiber are considered to be responsible for the formation of the periodic RIN structure. Here we investigate an influence of various factors on the period and positions of the RIN structure maxima. The results obtained can be used for designing single-frequency double-pass fiber amplifiers.

Asymmetric Atomic Coordination of Platinum Skin Layer on Intermetallic Platinum-Cobalt Particles.

Pt-based intermetallic alloy particles with a Pt skin layer have higher catalytic activity than solid-solution alloy particles and have attracted considerable attention for practical applications in polymer electrolyte fuel cells. However, the reason for the superior performance of intermetallic alloys is not yet fully understood. Because the catalytic reaction proceeds on the topmost surface of the particle, it is necessary to clarify the relationship between the periodic structure of the intermetallic alloy and the Pt atomic coordination on the surface. This study investigated the Pt-Pt interatomic distance of a Pt skin layer formed on intermetallic Pt3Co particles at atomic resolution through precise measurements using scanning transmission electron microscopy and theoretical calculations. The Pt atomic coordination on the surface shows good agreement between experimental observations and theoretical models, although the experimental image is a projection and thus provides indirect results. The theoretical calculation model revealed that structural relaxation at the Pt and Pt3Co interfaces led to two distinct Pt bonding states at the surface, including asymmetric atomic coordination. The asymmetric coordination of the Pt site deepens the d-band center, diversifies the oxygen adsorption energies, and enhances catalytic activity. Further exploration and control of the unique surface Pt coordination environments formed on the periodic structures of intermetallic alloys should reveal promising routes for the development of catalytic particles.

Heat Enhancement of Ethylene Glycol/Water Mixture in the Presence of Gyroid TPMS Structure: Experimental and Numerical Comparison

Cooling small components is becoming an attractive topic for researchers. In this paper, an attempt is made to use an ethylene glycol/water mixture as a cooling liquid. This liquid is a helpful application for when the fluid is in a harsh environment and should not freeze. The experiment uses an ethylene glycol/water mixture circulating through a triply periodic minimal surface structure (TPMS) made of aluminum and silver. A constant heat flux equal to 38,000 W/m2 is applied, and three different flow rates, 11.8 cm3/s, 15.5 cm3/s, and 19.6 cm3/s, are studied. The experimental setup is complemented with numerical modelling by solving the Navier–Stokes equation and the energy equation using the finite element technique. The flow is Newtonian, and a laminar regime is implemented. Results reveal that the performance of the ethylene glycol/water mixture did not enhance heat removal when compared to water. The average Nusselt number is similar regardless of the concentration of ethylene glycol in the mixture. This average Nusselt number, Nuaverage, in the presence of aluminum TPMS ranges between 60 and 80 (60 < Nuaverage < 80) and between 65 and 85 (65 < Nuaverage < 85) using silver TPMS. The increase in the mixture’s viscosity due to ethylene glycol increased the pressure drop. The performance evaluation criteria reach the maximum value of 90 when the mixture is composed of 5%vol ethylene glycol in water with aluminum TPMS. In the presence of silver TPMS, the maximum performance evaluation criterion is around 95 with a 5% ethylene glycol/water mixture. Finally, it is proven experimentally and confirmed numerically that the TPMS structure secures uniform heat extraction from the hot surface.

Infrared photoresponse of GeSiSn p-i-n photodiodes based on quantum dots, quantum wells, pseudomorphic and relaxed layers.

Structural and photoelectric properties of p-i-n photodiodes based on GeSiSn/Si multiple quantum dots both on Si and silicon-on-insulator (SOI) substrates were investigated. Elastic strained state of grown films was demonstrated by x-ray diffractometry. Annealing of p-i-n structures before the mesa fabrication can improve the ideality factor of current-voltage characteristics. The lowest dark current density of p-i-n photodiodes based on quantum dots at the reverse bias of 1 V reaches the value of 0.8 mA/cm2. The cutoff wavelength shifts to the long-wavelength region with the Sn content increase. Maximum cutoff wavelength value is found to be 2.6 μm. Moreover, multilayer periodic structures with GeSiSn/Ge quantum wells and GeSiSn relaxed layers on Ge substrates were obtained. Reciprocal space maps were used to study the strained state of GeSiSn layers. The optimal growth parameters were determined to obtain slightly relaxed GeSiSn layers. Designed p-i-n photodiodes based on these structures demonstrated the minimal dark current density of 0.7 mA/cm2 and the cutoff wavelength of about 2μm.

Extrapolation to the complete basis-set limit in density-functional theory using statistical learning

The numerical precision of density-functional-theory (DFT) calculations depends on a variety of computational parameters, one of the most critical being the basis-set size. The ultimate precision is reached in the limit of a complete basis set (CBS). Our aim in this work is to find a machine-learning model that extrapolates finite basis-size calculations to the CBS limit for periodic crystal structures. We start with a data set of 63 binary solids investigated with two all-electron DFT codes, and FHI-aims, which employ very different types of basis sets. A quantile-random-forest model and a symbolic regression approach using the SISSO model are used to estimate the total-energy correction with respect to a fully converged calculation as a function of the basis-set size. The random-forest model achieves a symmetric mean absolute percentage error of lower than 25% for both codes and outperforms previous approaches in the literature. SISSO outperforms the random forest model for the code. Our approach also provides prediction intervals, which quantify the uncertainty of the models' predictions. Published by the American Physical Society 2025

Infrared photoresponse of GeSiSn p-i-n photodiodes based on quantum dots, quantum wells, pseudomorphic and relaxed layers.

Structural and photoelectric properties of p-i-n photodiodes based on GeSiSn/Si multiple quantum dots both on Si and silicon-on-insulator (SOI) substrates were investigated. Elastic strained state of grown films was demonstrated by x-ray diffractometry. Annealing of p-i-n structures before the mesa fabrication can improve the ideality factor of current-voltage characteristics. The lowest dark current density of p-i-n photodiodes based on quantum dots at the reverse bias of 1 V reaches the value of 0.8 mA/cm2. The cutoff wavelength shifts to the long-wavelength region with the Sn content increase. Maximum cutoff wavelength value is found to be 2.6 μm. Moreover, multilayer periodic structures with GeSiSn/Ge quantum wells and GeSiSn relaxed layers on Ge substrates were obtained. Reciprocal space maps were used to study the strained state of GeSiSn layers. The optimal growth parameters were determined to obtain slightly relaxed GeSiSn layers. Designed p-i-n photodiodes based on these structures demonstrated the minimal dark current density of 0.7 mA/cm2 and the cutoff wavelength of about 2μm.

The Russian Church calls out to the world… From the history of the Soviet-American church forums of the Cold War Era

Relevance. In the current state of international relations, the historical experience of building and maintaining communication by actors of public diplomacy (confessional structures) in conflict periods is of particular importance. One of the most difficult periods in national history was the period of the Cold War between the Soviet Union and the United States. At the moment, however, the forces of the political and diplomatic structures of Russia's key historical denomination, the Russian Orthodox Church, were aimed at maintaining and developing a constant dialogue with the confessional organizations of the key geopolitical opponent. The central theme of this interaction was the international peacekeeping movement. It was designed to prevent the confrontation from escalating into an open conflict and formed a significant event agenda (events and forums) at which representatives of the church structures of two (and more often in a wider international composition) countries interacted, exchanged views and formed consolidated content: statements, notes, proclamations postulating the need to preserve peace in the name of higher Christian values and the preservation of lives.The purpose of the study is to examine the practice of church diplomatic activity of the hierarchy of the Russian Orthodox Church in the interaction of the Department of External Church Relations and the Publishing Department of the Moscow Patriarchate.Objectives: to reveal the specifics and characteristic features of the practical diplomatic organizational work of church structures in the organization of church forums in Soviet Russia in the early 1970s.Methodology. The principles of objectivity and historicism were applied during the research. To solve the tasks set by the author, historical-genetic, historical-systemic, historical-comparative, typological, retrospective methods were used.Results. The study of unique, previously unexplored and published sources allowed an unbiased reconstruction of the process of organizing a church forum in the development of the "peacekeeping activities" of the Russian Orthodox Church in the early 1970s.Conclusions. The sources demonstrate the development of the practice of church diplomatic work, allow us to reconstruct the specifics, course, timing, dynamics and circumstances of the organization of the peacekeeping forum of the Russian Orthodox Church in the conditions of Soviet reality in the early 1970s. The role of church structures is marked and described (the Publishing Department and its chairman, the Moscow Theological Academy), directly and formally unrelated to the conduct of international work.

Atomic Decompositions of Periodic Electronic-Structure Simulations.

We present a new theory for partitioning simulations of periodic and solid-state systems into physically sound atomic contributions at the level of Kohn-Sham density functional theory. Our theory is based on spatially localized linear combinations of crystalline Gaussian-type orbitals and, as such, capable of exposing local features within periodic electronic structures in a more intuitive and robust manner than alternatives based on the spatial distribution of atomic basis functions alone. Early decomposed cohesive energies of both molecular polymers and different crystalline polymorphs demonstrate how the atomic properties yielded by our theory convincingly align with the expected charge polarization in these systems, also whenever partial charges and Madelung energies may lend themselves somewhat ambiguous to interpretation.

Legacy Effects of Long-term Straw Returning on Straw Degradation and Microbial Communities of the Aftercrop

Straw incorporation can improve soil fertility and soil structure. While numerous studies have explored the immediate impacts of straw return on soil properties and crop production, the legacy effects of long-term straw return remain less understood. In this study, the straw returning soil of a continuous 15 years （SS） and non-straw returning soil （NS） were collected from Dahe Experimental Station of Hebei Academy of Agriculture and Forestry Sciences in China. The simulation experiments of subsequent straw return were carried out in pots by adding straw to the two types of soil （SS and NS）, in which the degradation rate of straw was determined using the sandbag method, the number of culturable microorganisms was counted through a dilution coating plate, and microbial communities were characterized using high-throughput sequencing. The findings revealed that compared with that in NS, SS significantly increased the degradation rate of 15 d and 30 d straw by 14.16% and 26.57%； the number of soil culturable fungi in 0-60 days by 43.10%-185.92%； and the number of cellulose-degrading bacteria by 55.12%-92.04% at 0 d, 42 d, and 56 d. Additionally, after straw returning for seven days, the bacterial ACE index, fungal ACE index, and Chao1 index in SS were lower than those in NS, indicating that the microbial community richness in SS was significantly reduced. At the phylum level of bacteria, the relative abundances of Acidobacteria, Rokubacteria, and Planctomycetes in SS increased observably, with an increase of 25.92%-45.17%. The relative abundances of the phyla of fungi such as Olpidiomycota, Zoopagomycota, and Glomeromycota increased markedly, with an increase of 12.09%-176.00%. At the genus level of bacteria, the relative abundances of uncultured_bacterium_c_Subgroup_6 and uncultured_bacterium_o_Rokubacteriales in SS increased significantly, with an increase of 28.91%-31.26%, and at the genus level of fungi, the relative abundances of Paecilomyces, Penicillium, and Moesziomyces were significantly increased by 2.98%-8.79%. Network analysis showed the SS bacterial network had a higher interaction degree and network connection, and the fungal network structure was more complex and stable than that of the NS. RDA results showed that soil microbial community composition was significantly correlated with straw degradation rate. SS showed obvious legacy effects on straw degradation, the number of soil culturable microorganisms, and population structure in a certain period, and the microbial flora of SS was more conducive to the degradation of the straws.

Recirculatory Solvotaxis of a Nematic Droplet on Water Surface Enabling Miniaturization.

Self-organized contact line instabilities (CLI) of a macroscopic liquid crystal (LC) droplet can be an ingenious pathway to generate a large collection of miniaturized LC drops. For example, when a larger drop of volatile solvent (e.g., hexane) is dispensed near a smaller LC drop resting on a soft and slippery surface of a nonsolvent (e.g., water), unique self-organized locomotion in the form of a twin vortex has been observed within the droplets. This phenomenon is driven by the rapid counter diffusion of hexane and LC between the two droplets, resulting in the formation of a pair of vortices within the droplets before instigating a CLI at the three-phase contact line (TPCL) of the LC droplet. Initially, the higher Laplace pressure inside the LC droplet (PL,5CB) due to a net pressure gradient, PL,5CB > PL,Hex, drives the LC toward hexane. However, as the volatile solvent droplet shrinks due to rapid evaporation, a flow reversal happens owing to PL,5CB < PL,Hex. Subsequently, the diffusion of hexane into the LC droplet and its subsequent evaporation manifest a periodic oscillatory CLI expansion and retraction at the TPCL, which in turn form periodic finger-like structures. Following this, the fingers with a higher aspect ratio break into an array of miniaturized satellite LC droplets undergoing Rayleigh-Plateau instability (RPI). The observed deviation in the normalized satellite droplet spacing compared to theoretical value affirm the stabilizing influence of LC elasticity in such fingers, where λ and R5CB are experimentally calculated droplet spacing and 5CB droplet radius. Control experiments elucidate the specific contributions of capillary, drag, solutal Marangoni, and osmotic forces to the 5CB droplet locomotion phenomena. The experimentally and analytically consistent demonstration also supports and predicts pressure drop-induced droplet velocities as v ∼ t1.16.

Multiphoton and Harmonic Imaging of Microarchitected Materials.

Microadditive manufacturing has revolutionized the production of complex, nano- to microscale components across various fields. This work investigates two-photon (2P) and three-photon (3P) fluorescence imaging, as well as third-harmonic generation (THG) microscopy, to examine periodic microarchitected lattice structures fabricated using multiphoton lithography (MPL). By immersing the structures in refractive index matching fluids, we demonstrate high-fidelity 3D reconstructions of both fluorescent structures using 2P and 3P microscopy as well as low-fluorescence structures using THG microscopy. These results show that multiphoton fluorescence (MPF) imaging offers reduced signal decay with respect to depth compared to single-photon techniques in the examined structures. We further demonstrate the ability to nondestructively identify intentional internal modifications of the structure that are not immediately visible with scanning electron microscope (SEM) images and compression-induced fractures, highlighting the potential of these techniques for quality control and defect detection in microadditively manufactured components.

Development of Micro/Nano Pattern Arrays with Grating-Based Periodic Structures using the Direct Laser Lithography System

Introduction: This research delves into utilizing the Direct Laser Lithography System to produce micro/nanopattern arrays with grating-based periodic structures. Initially, refining the variation in periodic structures within these arrays becomes a pivotal pursuit. This demands a deep comprehension of how structural variation aligns with specific applications, particularly in photonics and material science. Methods: Advancements in hardware, software, or process optimization techniques hold potential for reaching this objective. Using an optical beam, this system enables the engraving of moderate periodic and quasi-periodic structures, enhancing pattern formation in a three-dimensional environment. Through cost-effective direct-beam interferometry systems utilizing 405 nm GaN and 290 to 780 nm AlInGaN semiconductor laser diodes, patterns ranging from in period were created, employing 300 nm gratings. Results: The system's cost-efficiency and ability to achieve high-resolution permit the creation of both regular and irregular grating designs. By employing an optical head assembly from a bluray disc recorder, housing a semiconductor laser diode and an objective lens with an NA of 0.85, this system displays promising potential in progressing the fabrication of micro/nanopattern arrays. Conclusion: Assessing their optical, mechanical, and electrical properties and exploring potential applications across varied fields like optoelectronics, photovoltaics, sensors, and biomedical devices represent critical strides for further exploration and advancement.

Dynamical properties of the composed Logistic-Gauss map.

This study focuses on the analysis of a unique composition between two well-established models, known as the Logistic-Gauss map. The investigation cohesively transitions to an exploration of parameter space, essential for unraveling the complexity of dissipative mappings and understanding the intricate relationships between periodic structures and chaotic regions. By manipulating control parameters, our approach reveals intriguing patterns, with findings enriched by extreme orbits, trajectories that connect local maximum and minimum values of one-dimensional maps. This theory enhances our perception of structural organization and offers valuable perceptions of the system behaviors, contributing to an expanded understanding of chaos and periodicity in dynamic systems. The analysis reveals Complex Sets of Periodicity (CSP) in the parameter space, characterized by superstable curves that traverse their main bodies. The exploration of different combinations of parameters shows cascades of CSP structures with added periods and are organized based on extreme curves. This investigation offers valuable discoveries of the dynamics of dissipative mappings, opening avenues for future explorations in chaotic systems.

Transient chaos and periodic structures in a model of neuronal early afterdepolarization.

The presence of chaos is ubiquitous in mathematical models of neuroscience. In experimental neural systems, chaos was convincingly demonstrated in membranes, neurons, and small networks. However, its effects on the brain have long been debated. In this work, we use a three-dimensional map-based membrane potential model, the logistic KTz, to study chaos in single and coupled neurons. We first obtain an alternative phase diagram for the model using the interspike interval (ISI), evidencing a region of slow spikes (SS), missing from the original diagram of the KTz model. A large chaotic region is found inside the SS phase. Embedded in chaos are several self-similar periodic structures, such as shrimp-shaped domains and other structures. Sampling the behavior of neurons in this diagram, we detect a novel type of action potential, the neuronal early afterdepolarization (nEAD). EADs are pathological oscillations during the action potential, commonly found in cardiac cells and believed to be chaotic and responsible for generating arrhythmias in the heart. nEAD was found experimentally in neurons in a type of epilepsy. We study two chemically coupled neurons with this behavior. We identify and characterize transient chaos in their interaction. A phase diagram for this system presents a novel type of self-similar periodic structures, where the structures appear "chopped" in pieces.

Properties and Generalizations of Altered Jacobsthal Numbers Squared and their GCD Sequences

This paper investigates two types of altered Jacobsthal numbers, namely G(2)J(n) (a) and H(2)J(n) (a), which are obtained by adding or subtracting a specific value, denoted with {a}, from the square of the nth Jacobsthal numbers. These numbers exhibit a close relationship with the consecutive products of the Jacobsthal numbers. The study establishes consecutive sum-subtraction relations for the altered Jacobsthal numbers, and derives their Binet-like formulas. Furthermore, the greatest common divisor (Gcd) sequences of r-successive terms, represented by {G(2)J(n),r (a)} and {H(2)J(n),r (a)}, r ∈ {1, 2, 3, 4} are investigated. It is observed that these sequences display either a periodic or Jacobsthal structure.

Design of hybrid triply periodic minimal surface structures to enhance structural dynamic compression behavior

Design of hybrid triply periodic minimal surface structures to enhance structural dynamic compression behavior

Polarized p–n junction Si photodetector enabled by direct laser-induced periodic surface structuring

Polarized p–n junction Si photodetector enabled by direct laser-induced periodic surface structuring

A perfect ultra-wideband solar absorber with a multilayer stacked structure of Ti-SiO2-GaAs: structure and outstanding characteristics.

In this paper, we introduce an entirely new solar absorber design-a multi-layer periodic stacked structure. Through coupling effects, this design has perfect ultra-wideband absorption characteristics. The absorber structure is composed of four absorption units with varying cycle lengths, which are cyclically stacked on the surface of the refractory metal Cr. Each cycle encompasses three-layer nanosheets of Ti-SiO2-GaAs. We verify through finite difference time domain method (FDTD) simulations that the absorber achieves an absorption efficiency of 97.8% within the wavelength range of 280 nm to 3000 nm, with an average efficiency of 96.6% under the AM1.5 standard solar spectrum. The absorber can achieve such a remarkable absorption effect because of surface plasmon resonance (SPR) and Fabry-Pérot resonance effects. At 1500 K, this structure exhibits a thermal radiation efficiency of up to 97.83%. Furthermore, the design is not affected by polarization and it is less affected by the incident angle of the light source. These absorption spectra remain consistent regardless of whether it is in the TE or TM mode. Even when the angle of incidence is increased to 60 degrees, the absorption efficiency remains high. Its unique structure and excellent performance characteristics provide higher solar energy efficiency. These outstanding features enable solar absorbers to have broad application potential in improving solar energy efficiency.

Inverse design of triply periodic minimal surfaces structure based on point cloud generation network

Inverse design of triply periodic minimal surfaces structure based on point cloud generation network