Low Propagation Research Articles

Decoding the magnetic bit positioning error in a ferrimagnetic racetrack.

Current-driven motion of magnetic domain walls is one of the key technologies for developing storage class memory devices. Extensive studies have revealed a variety of material systems that exhibit high-speed and/or lower power propagation of the domain walls driven by electric current. However, few studies have assessed the reliability of the operations of the memory technology. Here, we decode the errors associated with writing and shifting domain walls using nanosecond current pulses in a ~5-micrometer-wide wire composed of a Pt/GdFeCo bilayer. We find that writing a domain wall at the edge of the wire causes a bit positioning error of ~0.3 micrometers, whereas the shifting process induces an error of ~0.1 micrometers per a 2-nanosecond-long current pulse. The error correlation among successive shifting is negligible when the current drive is sufficiently large. These features allow reliable operation of highly packed domain walls in a ferrimagnetic racetrack.

Temperature dependence of the deformation behavior and mechanical properties of a Fe–Mn–Al–C low-density steel for cryogenic application

The temperature dependence of the deformation behavior and mechanical properties of a Fe–20Mn–6Al-0.6C-0.15Si austenitic low-density steel was studied by tensile test and Charpy impact test at −196 °C, −77 °C and room temperature (RT), followed by microstructure analyses. The results indicate that the decreased tensile temperature, which is corresponding to reduced stacking fault energy (SFE), promotes the planar glide of dislocations. This led to larger fraction of low-angle grain boundaries (LAGBs) at lower tensile temperature. Consequently, both the tensile strength and elongation were improved as temperature decreased. At lower impact test temperature, the load and energy of crack initiation were larger, indicating a higher resistance to crack initiation. However, the transition from stable to unstable crack propagation occurred more rapidly at lower temperature, resulting in lower crack propagation energy and reduced resistance to crack propagation. This is because less region experienced planar glide. Due to the rapid unstable crack propagation, the Charpy absorbed energy at −196 °C was the lowest. The smaller fracture surface area, larger fibrous zone and more obvious ductile fracture characteristics in radial zone suggest that the toughness is better at higher temperature. Additionally, the presence of secondary cracks at RT delayed fracture, therefore benefitting toughness.

Effects of fissure locations on the crack propagation morphologies of 3D printing tunnel models: Experiments and numerical simulations

Hidden fissures widely exist in the surrounding rock of tunnels, and the propagations and interactions of the fissures will directly affect the safety and stability of tunnels. However, experimental and numerical simulation studies are scarce on the tunnel-fissure interactions under complex stress conditions. Based on this background, circular tunnel specimens with different prefabricated fissure locations are prepared by three-dimensional (3D) printing technology. Uniaxial compression fracture tests are conducted utilizing Digital Image Correlation (DIC) technology to obtain strain distributions. An improved Smoothed Particle Hydrodynamics (SPH) method is employed to simulate the crack propagation processes of the tunnel-fissure interactions. The results demonstrate the following: 1) Upper main cracks, upper side cracks, and lower side cracks are produced around the tunnel, and wing cracks initiate from the prefabricated fissure tips. 2) For the different intersection positions, wing crack propagation length decreases as the intersection position moves upward, while the lower side crack propagation length increases. 3) For different distances d, upper side crack does not appear, and the propagation length of upper main crack increases with the increase of the distance d. 4) For different fissure inclination angles α, upper main crack does not appear when α = 15°. The propagation length of wing crack increases with the increase of inclination angle α. 5) The peak stress increases as the intersection position moves upward, while it decreases with the increase of inclination angle α. With increasing distance d, the peak stress initially increases and then decreases. Finally, the crack initiation mechanisms under different fissure orientations and inclinations are discussed. These research findings provide valuable insights into the tunnel-fissure interaction mechanisms under complex stress conditions and the applications of the SPH method in underground engineering simulations.

Analysis of root-environment interactions reveals mechanical advantages of growth-driven penetration of roots.

Plant roots are considered highly efficient soil explorers. As opposed to the push-driven penetration strategy commonly used by many digging organisms, roots penetrate by growing, adding new cells at the tip, and elongating over a well-defined growth zone. However, a comprehensive understanding of the mechanical aspects associated with root penetration is currently lacking. We perform penetration experiments following Arabidopsis thaliana roots growing into an agar gel environment, and a needle of similar dimensions pushed into the same agar. We measure and compare the environmental deformations in both cases by following the displacement of fluorescent beads embedded within the gel, combining confocal microscopy and Digital Volume Correlation (DVC) analysis. We find that deformations are generally smaller for growing roots. To better understand the mechanical differences between the two penetration strategies, we develop a computational model informed by experiments. Simulations show that, compared to push-driven penetration, grow-driven penetration reduces frictional forces and mechanical work, with lower propagation of displacements in the surrounding medium. These findings shed light on the complex interaction of plant roots with their environment, providing a quantitative understanding based on a comparative approach.

Crack propagation kinetics under asymmetric cyclic loading for 316LN SS in high-temperature solution

Crack propagation rates (CPRs, or da/dN) of 316LN stainless steel (SS) in high-temperature solution under asymmetric cyclic loading conditions are experimentally determined, focusing primarily on the effect of load-rise time on crack propagation. The increment in crack propagation per cyclic block mainly occurs during the load-rise period. When the stress intensity factor range (ΔK) and load ratio (R) are kept similar, a faster increase in the stress intensity factor (dK/dt) during the load-rise period results in a lower average crack propagation rate (Vave-tr) during that phase. Secondary cracks and fatigue striations are observed on the fracture surface. The CPRs show a higher environmental enhancement factor (Fen) as the load-rise time increases.

To overcome the unconventional polymerization behavior of single-site symmetrical metallocene catalyst in the presence of borate

The β-H transfer of a propagating chain shows an unconventional polymerization behavior with single-site catalysts. In this work, we seek to address these challenges in the presence of different alkylaluminum cocatalysts. Adjusting the amount and type of cocatalyst in the polymerization process can affect molecular weight distribution (MWD) and chain ends formed via β-H transfer. The cocatalyst's elevated triethylelaluminum (TEA) by more than 50 % resulted in a drop in isoprene (IP) concentration, Mw, and activity, while pure TEA exhibited a smaller [C*]/[Zr] % than both pure Triisobutylaluminum (TIBA) and TIBA/TEA mixture. These results indicate that the type of alkylaluminum and its varying ratio affect the activation of metallocene catalysts. Secondly, this study also includes chain termination and transfer reactions and how comonomers participate in overcoming these issues. For this complicated process, we additionally performed the quench-labeling metal-polymer bonds technique (quantitative experiments (catalyst's active site)) leading to building a kinetic model that plays a significant role in mechanistic studies. The quantitative of active sites results indicate that the lower propagation rate constant (kp) was increased by nearly 20 % with TEA (25 %), and continuously increased with the TEA amount, meaning that TEA is a noticeable essential component in the cocatalyst for higher kp. The higher kpE and kpIP with TIBA might be associated with faster propagation and lower chain transfer reactions to Al−iBu and active centers and faster re-initiation of Al−iBu. The active center and 3,4 connections of IP are increased with increased TEA, meaning that the active site based on Al−Et bonds is facilitating more coordinated-to-IP through 3,4 connections. Finally, to clarify the impact of cocatalysts on MWD, a detailed theoretical splitting of the corresponding GPC was conducted. However, compared to PE MWD, TEA decreases the MWD of the polymers and becomes narrow. It is evident that introducing IP as a comonomer and TEA as a combined cocatalyst significantly reduces the chain transfer reaction that occurs during PE.

A SDN improvement scheme for multi‐path QUIC transmission in satellite networks

AbstractIn recent years, with the development of low‐earth orbit broadband satellites, the combination of multi‐path transmission and software‐defined networking (SDN) for satellite networks has seen rapid advancement. The integration of SDN and multi‐path transmission contributes to improving the efficiency of transmission and reducing network congestion. However, the current SDN controllers do not support the multi‐path QUIC protocol (MPQUIC), and the routing algorithm used in current satellite networks based on minimum hop count struggles to meet the real‐time requirements for some applications. Therefore, this paper designs and implements an SDN controller that supports the MPQUIC protocol and proposes a multi‐objective optimization‐based routing algorithm. This algorithm selects paths with lower propagation delays and higher available bandwidth for subflow transmission to improve transmission throughput. Considering the high‐speed mobility of satellite nodes and frequent link switching, this paper also designs a flow table update algorithm based on the predictability of satellite network topology. It enables proactive rerouting upon link switching, ensuring stable transmission. The performance of the proposed solution is evaluated through satellite network simulation environments. The experimental results highlight that SDN‐MPQUIC significantly improves performance metrics: it reduces average completion time by 37.3% to 59.3% compared to QSMPS and by 52.8% to 72.4% compared to Disjoint for files with different sizes. Additionally, SDN‐MPQUIC achieves an average throughput improvement of 81.4% compared to QSMPS and 147.8% compared to Disjoint, while demonstrating a 26.3% lower retransmission rate than QSMPS.

Effects of grain boundary phase distributions on mechanical characteristics of the high thermal conductivity AlN ceramics

AlN powders with different O impurity contents were used to fabricate the high thermal conductivity (TC) AlN ceramics of different grain boundary (GB) phase distributions via pressureless sintering. Bending strength, fracture toughness, R-curve characteristic, and fracture mechanism of the ceramics were then investigated. The results showed that the GB phase distributions had great influences on mechanical characteristics of the ceramics. The ceramics with the continuous/semi-continuous GB phases possessed low strength and toughness. Comparatively, the ceramics with the isolated island-like GB phases, especially the fine GB phases at the triple AlN GB junctions, owned higher strength and toughness. The AlN ceramics principally followed the intergranular fracture mode, but the GB phase distribution had great effects on the fractions of transgranular fracture. The AlN ceramics with the continuous/semi-continuous GB phases had a lower fraction of the transgranular fracture, and thus lower crack propagation resistance and reliability than the others.

Experimental study on the propagation characteristics of non-premixed H2/air flames in a curved micro-combustor

In this study, propagation characteristics of non-premixed H2/air flames in a curved micro-combustor were experimentally investigated. It was found that after cold-state ignition at the combustor exit, flames can propagate upstream and form a stable flame over a wide range of average inlet velocity (Vave,in) and nominal equivalence ratio (φ). The top-wall temperature distribution demonstrated that a flame separation phenomenon occurs when φ ≤ 1. High temperature zone of the combustor wall expanded and shifted downstream with an increasing Vave,in; however, with an increase in φ, it expanded initially and then shrank, and moved toward the air-side. The maximum wall temperature varied non-monotonically with both the Vave,in and φ, and they peaked at Vave,in = 1.5 m/s and φ = 1.6, respectively. Both lower and upper propagation limits (i.e., propagable velocities) exhibited non-monotonic tendencies versus φ. Specifically, the lowest and highest propagation limits are 0.3 m/s and 7.0 m/s, respectively, and they both occur at φ = 1.4. Empirical correlations of the propagation limits and propagable velocity range with φ were obtained. In summary, the present study demonstrated the feasibility of cold-state ignition of non-premixed H2/air for curved micro-combustors, and revealed the main flame propagation characteristics.

Impact of molybdenum disulfide diffused coir fiber on the physical, mechanical, thermal, and vibrational characteristics of polyester composites

AbstractThis research focuses on comparing the properties of molybdenum disulfide (MoS2) diffused coir fiber polyester composites (MCF‐PCs) with neat coir fiber polyester composites (NCF‐PCs) and exploring its applications in various industrial sectors such as automotive, construction and manufacturing, where mechanical strength and fire resistance are critical factors. The study aims to investigate the physical, mechanical, thermal degradation, fire performance, and vibration properties of these composites. Compression molding was used to develop composites with different coir fiber loadings (10%, 20%, and 30% by weight). MoS2 nanoparticles diffused on the fiber surface significantly improved mechanical characteristics, thermal stability, and fiber‐matrix compatibility. The findings indicate better crystallinity and physical properties in MCF‐PCs compared to NCF‐PCs. Morphological observations confirmed improved fiber‐matrix compatibility in MoS2‐diffused fiber composites with polyester. The MCF‐PC with 20% loading exhibited the highest tensile (28 ± 1.24 MPa), flexural (50 ± 0.50 MPa), and impact (15 ± 1.01 kJ/m2) strength. The flame retardancy of the composites was evaluated using a horizontal combustion test apparatus. In addition, MCF‐PCs exhibited better flame retardancy as evidenced by lower flame propagation velocity (9 ± 0.20 mm/min) and increased ignition time (13 ± 0.29 Sec). The MCF‐PC with 20% loading shows maximum natural frequencies of 77 ± 4.1 Hz.Highlights This study investigated MoS2‐diffused coir fiber‐reinforced polyester composites. Fiber‐matrix adhesion can be improved with modified fiber‐reinforced composites. The MoS2 diffusion on fibers improved the physical and mechanical properties of polyester composites. The MoS2 diffusion on fibers enhanced the thermal and vibrational characteristics of polyester composites. MoS2‐diffused natural fiber composites offer considerable research potential.

Resilience assessment of trade network in copper industry chain and the risk resistance capacity of core countries: Based on complex network

Copper is a critical mineral for the energy transition, facing significant risks of supply disruptions. To explore the copper industry chain's resistance to such risks, this article constructs a trade network for the global copper industry chain based on complex network methods, utilizing 2022 data on copper ores and concentrates, blister copper, refined copper, copper semis, and copper waste and scrap. It assesses the industry's resilience from both static and dynamic perspectives, and analyzes the risk resistance capacity of core countries. The results indicate that: (1) in the copper industry chain, copper semis, copper waste and scrap exhibit a relatively high level of overall resilience, but copper ores and concentrates, blister copper, and refined copper display a lower level of overall resilience. This indicates that the upstream of the copper industry chain is more susceptible to external factors than that of the downstream. (2) Targeted factors such as economic sanctions and trade disputes have a more serious impact on the copper industry chain than random factors such as natural disasters and transportation interruptions. Meanwhile, targeted factors have a stronger impact on the transmission efficiency and connectivity of the network. (3) There are significant communities in the copper industry chain, with some core countries playing an important role in connecting the network. In terms of connectivity, influence, and control, developed countries represented by the United States and the United Kingdom are stronger than the other two groups; emerging developed countries like Japan and South Korea exhibit lower propagation and intermediary capacities; emerging industrialized countries represented by Brazil and South Africa fall somewhere between the first two. Additionally, China and India demonstrate relatively important influence within the copper industry chain. Finally, this article provides policy recommendations for maintaining the stability of the copper industry chain and enhancing its resilience.

Hybrid plasmonic valley-Hall topological insulators

Abstract The emerging field of photonic topological insulators offers promising platforms for high-performance optical communication, computing, and sensing. However, conventional photonic topological insulator designs typically operate within the diffraction limit due to their dielectric nature. This limitation imposes constraints on device miniaturization, reduces light–matter interaction, and decreases overall device sensitivity. Introducing a new valley-Hall hybrid plasmonic topological insulator, we overcome this limitation by exploiting the coupling of surface plasmon oscillations with the optical modes of a dielectric photonic crystal, allowing for sub-diffraction vertical confinement of light. Deep-subwavelength chiral edge states can, therefore, be generated and robustly guided along disordered Z-shaped topological boundaries with much lower propagation loss compared to purely plasmonic platforms. Such extreme manipulation of light on an integrated chip platform maximizes light–matter interaction and opens the door for truly compact and efficient optical modulators, molecular sensors, and next-generation nanophotonic and quantum devices.

HEDV-Greedy: An Advanced Algorithm for Influence Maximization in Hypergraphs

Influence maximization (IM) has shown wide applicability in various fields over the past few decades, e.g., viral marketing, rumor control, and prevention of infectious diseases. Nevertheless, existing research on IM primarily focuses on ordinary networks with pairwise connections between nodes, which fall short in the representation of higher-order relations. Influence maximization on hypergraphs (HIM) has received limited research attention. A novel evaluation function, which aims to evaluate the spreading influence of selected nodes on hypergraphs, i.e., expected diffusion value on hypergraph (HEDV), is proposed in this work. Then, an advanced greedy-based algorithm, termed HEDV-greedy, is proposed to select seed nodes with maximum spreading influence on the hypergraph. We conduct extensive experiments on eight real-world hypergraph datasets, benchmarking HEDV-greedy against eight state-of-the-art methods for the HIM problem. Extensive experiments conducted on real-world datasets highlight the effectiveness and efficiency of our proposed methods. The HEDV-greedy algorithm demonstrates a marked reduction in time complexity by two orders of magnitude compared to the conventional greedy method. Moreover, HEDV-greedy outperforms other state-of-the-art algorithms across all datasets. Specifically, under conditions of lower propagation probability, HEDV-greedy exhibits an average improvement in solution accuracy of 25.76%.

Dayside Pc2 Waves Associated With Flux Transfer Events in a 3D Hybrid‐Vlasov Simulation

AbstractFlux transfer events (FTEs) are transient magnetic flux ropes at Earth's dayside magnetopause formed due to magnetic reconnection. As they move across the magnetopause surface, they can generate disturbances in the ultralow frequency (ULF) range, which then propagate into the magnetosphere. This study provides evidence of ULF waves in the Pc2 wave frequency range (>0.1 Hz) caused by FTEs during dayside reconnection using a global 3D hybrid‐Vlasov simulation (Vlasiator). These waves resulted from FTE formation and propagation at the magnetopause are particularly associated with large, rapidly moving FTEs. The wave power is stronger in the morning than afternoon, showing local time asymmetry. In the pre and postnoon equatorial regions, significant poloidal and toroidal components are present alongside the compressional component. The noon sector, with fewer FTEs, has lower wave power and limited magnetospheric propagation.

Waveguide Eavesdropping Threat for Terahertz Wireless Communications

As wireless communications move to higher frequency band for 5G networks and beyond, resiliency against eavesdropping and other security threats is still one of the key system-design considerations. Compared to data transmissions by lower frequencies, terahertz links are inherently more robust against eavesdropping attacks due to their propagation characteristics (such as high free-space path loss) and aligned link path by high-gain antennas. However, it does not indicate that eavesdropping is always impossible. Line-of-sight terahertz links have proven to be vulnerable to active/passive eavesdroppers by placing scatters in the path of data transmission, or by collecting side-lobe leakages. Here, we demonstrate a waveguide-based approach for signal eavesdropping which can be operated much more feasibly with several advantages, such as lower propagation loss and reliable data interception. Our method relies on a 3D printed rectangular dielectric waveguide and can overcome spatial limitations caused by directional modulation or near-field modulation. We demonstrate successful eavesdropping attacks for a 16 quadrature amplitude modulated (16-QAM) data link at rates up to 5 gigabits per second. Our work highlights the importance of system designs in resisting waveguide-based eavesdropping strategies and identifies aspects where

Full-temperature performance characterisation of super tough resin concrete for steel bridge deck paving

ABSTRACT The severe service environment of steel bridges put forward strict requirements for the deck pavement, especially the flexibility of paving materials. In this study, a new super tough resin-based concrete (STRC) was introduced and a comparative study of STRC and epoxy asphalt concrete (EAC) performance was conducted. Specifically, the high-temperature stability, low- and intermediate-temperature flexibility, fracture resistance, and fatigue properties were characterised by the dynamic creep test, beam bending test, semi-circular bending test, and semi-circular fatigue test, respectively. According to the results, at 70°C, the cumulative strain after 10,000 cycles of loading is about 2700μϵ and 900μϵ for STRC and EAC, respectively. At −10°C, the maximum tensile strain of EAC is only 2419 μϵ, which is significantly lower than that of STRC (17000 μϵ). For the cracking resistance, STRC exhibits larger total fracture energy, pre-peak and post-peak fracture energies, which indicates the excellent cracking resistance of STRC. Furthermore, the fatigue life and accumulated dissipated energy of STRC are higher than that of EAC. Besides, the tensile strain growth rate of EAC is significantly greater than that of STRC, which implies a lower crack propagation rate and better fatigue resistance of STRC.

Comprehensive FR1(C) and FR3 Lower and Upper Mid-Band Propagation and Material Penetration Loss Measurements and Channel Models in Indoor Environment for 5G and 6G

Comprehensive FR1(C) and FR3 Lower and Upper Mid-Band Propagation and Material Penetration Loss Measurements and Channel Models in Indoor Environment for 5G and 6G

Accelerated ignition-shock coupling and deflagration to detonation transition by ozone kinetic enhancement of dimethyl ether mixture

This study aims to understand the effect of kinetic enhancement by ozone addition on the Deflagration to Detonation Transition (DDT) and ignition-shock coupling in a microchannel using dimethyl ether (DME). Simultaneous high-speed chemiluminescence and shadowgraph imaging are carried out to analyze the flame front propagation, shock wave structures, autoignition, and ignition-shock coupling during the DDT process. The experimental results show that for all cases, with and without ozone kinetic enhancement, autoignition and DDT always occur in a reactivity gradient region with oblique shock cluster between the flame front and the flame acceleration-induced precursor shock. The observed DDT occurs via the Zeldovich hot spot gradient mechanism through the following stages: (1) Oblique shock cluster formation and acoustic compression between the flame front and the precursor shock, (2) autoignition initiation in the oblique shock cluster region, (3) spontaneous ignition wave propagation, and (4) ignition-shock coupling. It is found that autoignition location, oblique shock strength, induction zone length, ignition-shock coupling, and DDT onset flame velocity are very different from ozone kinetic enhancement. As the ozone addition is higher, the autoignition is advanced and the ignition location moves farther ahead of the flame front at a lower flame front propagation speed and weaker oblique shock clusters. Two different ignition-shock coupling modes are identified depending on ozone concentration. Without ozone kinetic enhancement, DDT occurs via ignition wave coupling with the precursor shock. However, ozone addition can accelerate the autoignition and initiate a direct ignition-shock coupling for DDT without interaction with the precursor shock. The present results show that kinetic enhancement in autoignition using an ignition enhancer such as ozone or plasma is critical and effective in accelerating and controlling DDT.

How Artifact-Based and Authority-Based Coordination Affect Propagation Costs in Open Source Software Development

The success of open source software (OSS) projects depends on their ability to produce software architectures with low propagation costs, as such architectures demand little effort from developers. This study focuses on the project’s form of coordination—the way in which interdependent contributions are managed—as a driving force behind propagation costs. It distinguishes between two coordination archetypes. First, artifact-based coordination is found in egalitarian projects, in which developers only use the work artifact (the architecture itself), without direct interaction, to coordinate. Second, authority-based coordination is used in hierarchical projects (e.g., Linux Kernel) or when companies pay developers for their work. Using a computational model, this study compares these two coordination mechanisms by simulating how they build software architectures (formalized as design structure matrices) from interdependent contributions. As a contextual condition, the model considers the degree of architecture visibility, which is the developers’ (in)ability to see recent additions to the architecture. The model provides two insights. First, artifact-based coordination, as compared to authority-based coordination, generally leads to lower propagation costs. Second, decreasing the degree of architecture visibility reduces propagation costs, an effect that I describe as focal-layered superposition. These insights contribute to the literatures on coordination in OSS development and the mirroring hypothesis. They also have practical implications for the creation of preferable architectures in OSS development.

Distinct avalanche dynamics detected in metallic glasses with high energy state revealing the crack-like shear banding mechanism

When a sufficiently high stress is applied to a metallic glass, causing plastic deformation, the material undergoes structural reconfiguration through dissipative slip avalanche events that release local stresses. By utilizing isothermal annealing and cold rolling techniques to tune the energy levels of metallic glasses, it has been observed that structural rejuvenation is accompanied by structural relaxation, as evidenced by distinct changes in avalanche dynamics. We present detailed statistics of the avalanche dynamics during shear band formation in energy-tuned metallic glasses, ranging from structurally relaxed to rejuvenated states. By analyzing shear band characteristics and examining scaling exponents, avalanche durations, and stress relaxation rates, we can establish a connection between the local activation of shear transformation zones and the formation of macroscopic shear bands. The statistics of avalanche duration indicate that an increase in soft zones within metallic glasses can alleviate stress release and stabilize plastic flow, as evidenced by the characteristics of shear bands. We attribute the significant transition of serrated flow, observed at different energy levels (i.e., as-cast, relaxed, and rejuvenated states) to the variations in nucleation and multiplication of shear bands that originate from local weak spots. Analysis of the distinct avalanche dynamics suggests that in lower energy level metallic glasses, the nucleation and propagation of shear bands exhibit localized crack-like behavior, while in higher energy level metallic glasses, they display diffused crack-like characteristics. Indeed, our results strongly support that the decreased avalanches observed in the high energy level metallic glasses originate from the nucleation of numerous small shear bands, which directly compete with the propagation of the main local shear band. These findings deepen our fundamental understanding of the relationship between the microscopic mechanism of slip avalanche dynamics and shear banding, providing a pathway to control the plasticity of metallic glasses.