Mode Shift Research Articles

FACTORS INFLUENCING PRE- AND POST-COVID-19 TRANSPORT MODE SHIFT IN WORKPLACE TRAVEL

The current modal share between private and public transport in Malaysia still falls short of its 50:50 goal. The continued reliance on private transport for workplace travel faces further aggravation in light of the Covid-19 pandemic. Aiming to understand this concern, this study pursued two key objectives; (i) to explore shifts in transport mode choices before and after Covid-19; and (ii) to identify the significant factors influencing these shifts. This cross-sectional study was conducted in Kuala Lumpur, Malaysia, focusing specifically on workplace commuting (n=113). The McNemar’s test was used to determine the significance of transport mode shifts from public to private transport and vice versa, while the Mann-Whitney U test was employed to determine the significance of various factors on these shifts. Four primary factors were examined: cost, accessibility, comfort, and hygiene concerns. The findings showed that (i) a discernible shift in transport modes occurred (Q= 38.72, p>.05), with a notable trend of individuals transitioning from public to private transport due to the Covid-19 pandemic; (ii) hygiene concerns (mean rank= 72.36, U= 807.0, p<.000) and comfort (mean rank= 64.73, U= 1188.5, p= .013) emerged as statistically significant influencers of this shift; and (iii) while cost (mean rank= 65.28, U= 1053.5, p= .001) is an important determinant of transport mode preferences, it was not found to be a significant factor driving mode shifts. A comprehensive examination of pandemic-induced transport mode preferences yields crucial insights for shaping transportation infrastructure and services, facilitating sustainable development in line with UN SDGs. Understanding these influences is vital for effective policy-making and achieving desired modal shares.

A correlation between hydroxyl vibrations under compression and anharmonicity: glaucophane as a test case

The infrared hydroxyl bands and first hydroxyl combination bands of glaucophane are characterized under pressure. In this weakly hydrogen-bonded mineral, the anharmonicity parameter, as determined from the difference between combinations and the fundamentals, is nearly constant with pressure to 15 GPa, indicating that the ambient pressure value of hydroxyl-bond anharmonicity closely reflects its value at high pressures. Given this near-constancy, the Grüneisen parameters of the hydroxyl stretching vibrations of a wide range of minerals, as derived from the pressure dependence of their O–H stretching frequencies, are correlated with the anharmonic parameter of each vibration, as determined from the ambient pressure offset of the summed frequencies of the fundamental n = 0 to 1 transitions and the frequency of the hydroxyl combination or overtone band corresponding to the n = 0 to 2 transition. This correlation is motivated by (1) the anharmonic origin of the Grüneisen parameter; and (2) the grossly similar form of the interatomic potential governing weak- and medium-strength hydrogen bonding in many minerals. This possible correlation provides a means through which the likely pressure-induced hydroxyl mode shifts of phases might be estimated from ambient pressure near-infrared measurements and emphasizes the importance of near-infrared combination/overtone band measurements. In this context, the combination/overtone bands of high-pressure hydrous phases are almost completely uncharacterized, and thus one probe of their anharmonicity has been neglected. Such information directly constrains the nature of hydrogen bonding in these phases, and hence provides possible insights into both their retention of hydrogen and its mobility. Deviations from the anharmonicity-Grüneisen parameter correlation, when observed (as may be the case in prehnite), could provide insights into anomalous effects on the hydroxyl potential well induced by bifurcated H-bonds, pressure-dependent Davydov splitting, or the influence of neighboring cations.

US road safety during COVID-19: motorist, pedestrian and bicyclist fatality trends

Purpose The purpose of this paper is to illustrate how COVID-19 lockdowns in the USA impacted traffic safety. Design/methodology/approach The authors explored the role of vehicle, user and built environment factors on traffic fatalities in the USA, comparing results during COVID-19 lockdowns (March 19th through April 30th, 2020) to results for the same time period during the five preceding years. The authors accomplished this through proportional comparisons and negative binomial regression models. Findings While traffic levels were 30%–50% below normal during the COVID-19 lockdowns, all traffic fatalities decreased by 18.3%, pedestrian fatalities decreased by 19.0% and bicyclist fatalities increased by 3.6%. Fatal COVID-19 crashes were more likely single-vehicle crashes involving fixed objects or rollovers. COVID-19 traffic fatalities were most common on arterial roadways and in lower density suburban built environments. Findings suggest the importance of vulnerable road users, speed management and holistic built environment policy when pursuing safety on the streets. Originality/value The findings have road safety implications not only for future pandemics and other similar events where we would expect decreases in motor vehicle volumes (such as natural disasters and economic downturns) but also for cities that are pursuing mode shift away from personal automobiles and toward alternative modes of transportation.

Electrical and optical properties of polyamide 6 nanocomposites with multi-walled carbon nanotubes

In this work, quantum chemical modeling, electrical conductivity, Raman scattering, and photoluminescence of polyamide 6 nanocomposites with multi-walled carbon nanotubes (0–2.5 vol%) were investigated. It was shown that the concentration dependence of the electrical conductivity obeys the percolation theory and has the value of percolation threshold 1.41 vol%. The conductivity value of the composite at 2.5 vol% nanotubes is 1.1*10-3 S/cm. It was found that in PA6 nanocomposites filled with MWCNT an increase in the concentration of nanotubes from 0.001 to 0.015 vol%, namely in the pre-percolation region of electrical conductivity, due to a significant restructuring of the Raman spectra, which consists in a shift of the vibrational modes of the methylene groups CH2 and amide I, as well as in a change of their relative intensities. From the photoluminescence spectra of PA6-MWCNT, it can be seen, that the carbon nanotubes largely determine the conformational changes in the polymer matrix and have little effect on the defective structure of the polymer itself.The goal: to establish the mechanisms of electrical conductivity and the interaction of nanotubes with polyamide macromolecules and its influence on the electronic and optical properties of nanocomposites of polyamide multi-walled carbon nanotubes.

Experimental study on ignition and blowout characteristics of dual combined flame stabilizers in scramjet

The ignition and blowout characteristics have a significant impact on the performance and operating limit of the scramjet. In this study, direct-connected ground tests of a typical scramjet combustor have been conducted to simulate the high-altitude flight condition of Mach 6. The incoming air has a total temperature of 1689 K and a dynamic pressure of 30 kPa. The ignition and blowout characteristics of the dual strut/cavity combined flame stabilizers in the scramjet are obtained. The immediate response of pressure at key positions is used to analyze the forward propagation characteristics of pressure during the ignition process and the pressure variation during the flame blowout process. The flame distribution and temperature variation during the ignition and blowout processes are obtained by high-speed photography, OH⁎ spontaneous radiation photography, spectrometer and multispectral imaging equipment. Results indicate that the process from local ignition to global ignition successfully has durations lasting for hundreds of milliseconds, comprising four stages with two pressure lift stages. The flame diffusing forward and upstream cavity igniting successfully are the main processes, constituting 60% and 30% of the duration, respectively. During the ignition process, the pressure response time of the two-stage cavity differs by several milliseconds. And the flame is transmitted forward to the upstream cavity through combustor walls. As the ignition process progresses under high equivalent ratio (ER) conditions, flame stabilization mode shifts from stabilizing flame in the recirculation zone of the cavity to stabilizing flame in the shear layer of the strut. Upon completion of global ignition, the flame temperature at the shear layer of the cavity upstream exceeds 2700 K, but decreases to 2125 K as the core reaction zone is shifted from the top of the strut to the tail and bottom of the cavity when the ER decreases. Two pressure drops occur during the flame blowout process, and the critical ER of the global blowout is approximately 0.33. The primary shear layer flame is blown out during the first pressure drop, and the intensity of the cavity flame decreases. Finally, the second pressure drop occurs as the flame in the cavity moves downstream and extinguishes.

Dynamic splitting response and mechanical effect of joint angle in sandstone containing various weak-filling joints

Weak-filling joints substantially degrade the integrity and load-bearing capacity of rock masses, thus increasing the complexity and unpredictability of their mechanical response behavior. One of the main mechanical properties of jointed rocks is their splitting performance, which heavily influences their failure mode. To study the effects of joint angles on splitting mechanical properties, we conducted dynamic splitting tests on sandstone samples with seven different inclination angles of weak-filling joints. These tests were conducted using the Brazilian disc method and a modified split Hopkinson bar apparatus. The splitting mechanical response, energy rate characteristics, joint angle damage factors, failure modes, micromorphology characteristics, and the mechanical effects of joint angles were systematically analyzed. The findings suggested that varying joint angles led to different initial damage levels in the rock mass, which can be described by a power exponential function. The observed relationship between peak load and joint angle was corroborated by integrating a damage parameter into the theoretical derivation of the mechanical effect of the joint angle. Weak-filling joints reduced the brittle failure characteristics and peak loads of the samples but enhanced their ability to deform. Furthermore, the energy reflection rate exhibited an inverse relationship with the joint angle, which is contrary to the trends observed in energy transmission and absorption rates. Additionally, both macroscopic and microscopic morphology analyses confirmed that the joint angle primarily determined the fracture trajectory of the samples, causing a gradual shift in the failure modes of jointed samples from shear to tensile failure.

Bandwidth enhancement of substrate integrated waveguide cavity-backed half bow-tie complementary-ring slot antenna for Ku-band applications

The proposed antenna introduces a wideband double-resonance substrate-integrated waveguide (SIW) cavity-backed slot antenna with shorting vias. The antenna is compact and has a wide frequency range. By loading the SIW cavity slot with shorting pin/vias, the authors describe the mechanism of operation and electric field distributions of the double resonance antenna. By etching the HBT-CRS at the center of the cavity, which creates the dual modes. One is an upward shift in the lowest mode (TE 120 mode or TE 210 mode) and a downward shift in the highest mode (TE 320 modes/TE 230 modes), and these two are paired together. As a result, the fabricated antenna has a very large bandwidth and a strong sense of double resonance. The antenna is designed, and then prototypes are built and tested. The key benefits are compactness, low fabrication cost, performance, and ease of integration with planar circuitry. SIW antennas are impactful in present wireless communication systems. A simulated double resonance design antenna with a low profile of 0.05 λ0 (free-space wavelength) has a bandwidth of 1.854 GHz (frequency range varies from 12.58 - 14.38 GHz and fractional bandwidth of 13.93%) and a peak gain of 6.56 dBi across the whole bandwidth while measured bandwidth is 2 GHz (frequency range from 12.5 - 14.5 GHz and fractional bandwidth of 14.81%) and the gain over the entire bandwidth is 6.46 dBi. In addition, the antenna has outstanding unidirectional radiation characteristics for Ku band applications.

Trends in varying modes of drug use in opioid toxicity deaths in Ontario from 2017 to 2021.

Preliminary data indicate a shift toward inhalation instead of injection in opioid toxicity deaths. Understanding changing modes of drug use is essential to addressing the North American drug toxicity crisis driven primarily by unregulated fentanyl. This study aims to comprehensively characterize this shift across Ontario, Canada. We conducted a population-based repeated cross-sectional study of accidental opioid toxicity deaths in Ontario from July 1, 2017 to June 30, 2021. For each quarter of the study period, the number and percent of deaths by mode of drug use (inhalation only, injection only, both or other) were reported. Descriptive characteristics were reported in the last two years of the study. There were 6687 accidental opioid toxicity deaths in Ontario over the study period, with a 62.1% increase in the quarterly number of deaths observed. The prevalence of deaths where inhalation was the only mode of drug use almost doubled, rising from 22.0% to 43.5%. There was a corresponding 64.4% decrease in opioid toxicity deaths with indication of injection alone (29.0% to 10.3%). This study reveals a shift in mode of drug use toward inhalation that is increasingly contributing to opioid toxicity deaths in Ontario. Understanding the shifts in patterns of opioid use serves to provide essential insights into more effective harm reduction and treatment approaches to address the drug toxicity crisis.

Influence of external circuitry on CF4 breakdown process in capacitively coupled plasma

Capacitively coupled plasma (CCP) tools are crucial for etching, deposition, and cleaning processes in the semiconductor industry. A comprehensive understanding of their discharge characteristics is vital for the advancement of chip processing technology. In this study, the influence of external circuitry on the breakdown process was investigated under the CF4 discharge system, with a particular focus on challenges presented by the nonlinear nature of the plasma. The results demonstrated that the external circuit significantly affects the discharge process by altering the electric field distribution as well as modifying the electron density and temperature of the plasma. By incorporating the matching circuit, stable discharge was achieved at reduced voltage levels. During breakdown, a substantial increase in the capacitance of the discharge chamber is induced by the formation of the sheath, which alters the amplitude of the electrical signal within the external circuit. The breakdown characteristics are significantly influenced by the capacitance of the matching network. Breakdowns with distinctive characteristics can be achieved by selectively choosing different capacitors. Furthermore, a shift in the CF4 discharge mode at different pressures under the external circuit model and the alteration in the discharge mode affect the electrical properties of the plasma in the matched circuit. These findings could be used to optimize the discharge of CCP and its applications, including surface treatment, material synthesis, and environmental remediation.

Analysis of the impact of the railway allowance policy and the increase in fines for loaded trucks on the transfer of modes to rail transportation types

Currently, cargo trucks dominate logistics transportation, so the condition of the Pantura (Java North Coast Road) route is quite poor and often suffers severe damage even though it has been repaired. If there is no solution to the high volume of trucks on the coastal route, then the budget for repairing the coastal route will continue to increase, so researchers want to minimize the repair of the coastal route by switching modes from trucks to trains. One of the ways that previous researchers have found is one of the policies to be able to support mode shift by giving allowance to trains and increasing the fines of freight trucks. Therefore, researchers investigated many policies connected to the increase in fines for freight vehicles on the railway, as well as allowances. Analysis regarding the impact caused by the policy will be included. According to the SEM-PLS model, preferences are indirectly impacted by existing and perceptions, with existing and perceptions intermediary path scores with high preferences. The fines variable, on the other hand, is not a good preference for mode shift policies. Business merchants that have a positive perception of rail transportation offered a considerably greater response for rail transportation allowances. Therefore, they will seek to utilize the train. The perception variable influenced the amount of the proposed train allowance policy, but not the freight truck fines policy. Train allowance and truck fines policies can be utilized in conjunction with one another, depending on the logistical conditions in a given location. Because this is a logistics network in Indonesia, an archipelago country where trucks are more flexible if they want to travel between islands, train allowance is the best choice to support mode shift persuasively and maximize the potential of trains for travel within the island

Soft solid subwavelength plates with periodic inclusions: Effects on acoustic Transmission Loss

Dispersion and scattering properties of a soft solid plate with solid cylindrical inclusions embedded in are theoretically and numerically reported in this work. The system is numerically analyzed considering both the vibroacoustic coupling and the presence of viscoelastic losses. In addition to the mechanical properties of the soft solid plate that allows the shift of the higher order Lamb modes to the low audible frequency domain, the presence of the inclusions introduces resonant and antiresonant phenomena in the subwavelength regime, leading to an elastic band-gap and a destructive modal interference in the soft solid plate able to interact with each other. These phenomena are used to design a system with strong transmission loss, breaking the mass law by 15 dB, and with subwavelength dimensions as the thickness is 32 times smaller than the equivalent wavelength in air. These performances are both computed and tested experimentally using a standard measuring process.

Effect of SiO2 protective layer on LiNbO3 structured SAW resonators and temperature characteristics study

In this paper, using LiNbO3 as the piezoelectric substrate, Pt as the electrode and SiO2 as the protective layer, a multi-physics field coupled finite element model was used to investigate the effect of the protective layer thickness on the Rayleigh wave propagation characteristics, and the relationship between the protective layer thickness and the frequency–temperature coefficient TCF and electromechanical coupling coefficient K 2 is established. The frequency characteristics of the device and the microscopic changes of the electrode and substrate structures under high temperature were analyzed experimentally. The results show that no acoustic mode shift occurs when the normalized thickness is less than 31.25%. As the thickness of the protective layer increases, the vibration displacement in the direction of L wave, SH wave and SV wave decreases, and the thickness of the protective layer can be increased appropriately to reduce the interference of SH wave to Rayleigh wave; |TCF| decreases with increasing thickness of the protective layer. Changes in the thickness of the protective layer at different temperatures lead to fluctuations in K 2; the protective layer structure leads to a slight decrease in Q value. As the temperature increases, the fluctuation of the resonant frequency of the SAW resonator increases. The SiO2 protective layer can effectively protect LiNbO3 materials while improving the high-temperature working stability of Pt electrodes.

High-pressure response of vibrational properties of b-As x P1–x : in situ Raman studies

The structural evolution of black arsenic-phosphorous (b-As x P1–x ) alloys with varying arsenic concentrations was investigated under hydrostatic pressure using in situ Raman spectroscopy. High-pressure experiments were conducted using a diamond anvil cell, which revealed pressure-induced shifts in vibrational modes associated with P–P bonds (A 1 g , A 2 g , ), As–As bonds (A 1 g , A 2 g , ), and As–P bonds in b-As x P1–x alloys. Two distinct pressure regimes were observed. In the first regime (region I), all vibrational modes exhibited a monotonic upshift, indicating phonon hardening due to hydrostatic pressure. In the second regime (region II), As0.4P0.6 and As0.6P0.4 alloys displayed a linear blueshift (or negligible change in some modes) at a reduced rate, suggesting local structural reorganization with less compression on the bonds. Notably, the alloy with the highest As concentration, As0.8P0.2, exhibited anomalous behavior in the second pressure regime, with a downward shift observed in all As–As and As–P Raman modes (and some P–P modes). Interestingly, the emergence of new peaks corresponding to the Eg mode and A 1g mode of the gray-As phase was observed in this pressure range, indicating compressive strain-induced structural changes. The anomalous change in region II confirms the formation of a new local structure, characterized by elongation of the P–P, As–As, and As–P bonds along the zigzag direction within the b-As x P1–x phase, possibly near the grain boundary. Additionally, a gray-As phase undergoes compressive structural changes. This study underscores the significance of pressure in inducing structural transformations and exploring novel phases in two-dimensional materials, including b-As x P1–x alloys.

Influence of sintering aids on properties of dense Si2N2O ceramic developed by spark plasma sintering

Through reactive liquid phase sintering, dense and homogenous pellets with a diameter of 40 mm were successfully achieved after 50 min. These samples contain at least 95 vol% of Si2N2O. The microstructure, fracture toughness, coefficient of thermal expansion (673–1673 K), dielectric properties and high-temperature oxidation resistance were investigated to determine the influence of sintering aids such as lanthanide oxides (Sm2O3 and Y2O3) and metal oxide (Al2O3). The nano-sized grains generated have a uniform distribution. The composition of the sintering aid has no influence on the coefficient of thermal expansion or the dielectric properties. The crack propagation mode shifts from transgranular to intergranular in Al2O3 samples, which increases the fracture toughness. The lanthanide oxide samples, on the other hand, outperform the Al2O3 samples in terms of oxidation resistance, as a protective SiO2 and Ln2Si2O7 layer forms on the surface of the oxidized samples.

Using System Dynamics Approach to Explore the Mode Shift between Automated Vehicles, Conventional Vehicles, and Public Transport in Melbourne, Australia.

With the increasing use of automated vehicles (AVs) in the coming decades, government authorities and private companies must leverage their potential disruption to benefit society. Few studies have considered the impact of AVs towards mode shift by considering a range of factors at the city level, especially in Australia. To address this knowledge gap, we developed a system dynamic (SD)-based model to explore the mode shift between conventional vehicles (CVs), AVs, and public transport (PT) by systematically considering a range of factors, such as road network, vehicle cost, public transport supply, and congestion level. By using Melbourne's Transport Network as a case study, the model simulates the mode shift among AVs, CVs, and PT modes in the transportation system over 50 years, starting from 2018, with the adoption of AVs beginning in 2025. Inputs such as current traffic, road capacity, public perception, and technological advancement of AVs are used to assess the effects of different policy options on the transport systems. The data source used is from the Victorian Integrated Transport Model (VITM), provided by the Department of Transport and Planning, Melbourne, Australia, data from the existing literature, and authors' assumptions. To our best knowledge, this is the first time using an SD model to investigate the impacts of AVs on mode shift in the Australian context. The findings suggest that AVs will gradually replace CVs as another primary mode of transportation. However, PT will still play a significant role in the transportation system, accounting for 50% of total trips by person after 2058. Cost is the most critical factor affecting AV adoption rates, followed by road network capacity and awareness programs. This study also identifies the need for future research to investigate the induced demand for travel due to the adoption of AVs and the application of equilibrium constraints to the traffic assignment model to increase model accuracy. These findings can be helpful for policymakers and stakeholders to make informed decisions regarding AV adoption policies and strategies.

Large area synthesis of mono/few-layer MoS2 thin films on thermal oxide silicon substrate by pulsed laser deposition technique

Two-dimensional molybdenum disulphide (2D MoS2) has emerged as an auspicious material in the development of optoelectronic devices owing to its remarkable similarities with graphene while possessing a definite bandgap. However, the production of these devices is restricted due to the difficulties in producing high-quality 2D MoS2 films on a large scale. Here we report the growth of mono/few layers of MoS2 - on thermal oxide silicon (Si/SiO2) substrate using pulsed laser deposition (PLD). The presence of Raman peaks corresponding to A1g and E12g modes of vibration confirmed the formation of 2D MoS2. The difference in Raman shift of A1g and E12g modes was used to find out the number of layers of the PLD-grown MoS2 thin films, which was found to be increasing with deposition time. Photoluminescence spectra also revealed the formation of mono/few-layered MoS2 thin films, and the thickness of the films was determined using atomic force microscopy. The MoS2 thin films were then deposited on a quartz substrate to record the absorption spectra of MoS2, and the existence of four excitonic peaks A, B and C, D further confirmed the formation of 2H MoS2. The calculation of the bandgap was done using Tauc plot studies, and a bandgap value of 1.77 eV was obtained for monolayer MoS2. The stoichiometry of Mo and S in the PLD-grown samples was determined using X-ray photoelectron spectroscopy analysis. The morphology and crystallinity of the monolayer MoS2 were studied by performing transmission electron microscopy analysis.

Detection of SARS‐CoV‐2 Virus Concentration Using a Simple Structure of Binary Photonic Crystal Sensor

The scientific community works hard on developing reliable, rapid, highly sensitive, and low‐cost techniques to detect severe acute respiratory syndrome coronavirus‐2 (SARS‐CoV‐2). The current techniques can occasionally produce false‐positive results. The development of novel approaches for the identification of SARS‐CoV‐2 is a significant area of research because of the limitations of current methods. A biosensor based on a defective binary photonic crystal (PCL) is proposed to detect SARS‐CoV‐2 concentration herein. The model of pathogen concentration‐dependent refractive index of the analyte is taken into consideration. The concept of operation of the PCL sensor is based on the defect mode shift when any change in the refractive index of the defect layer occurs. The transmission spectra of the PCL are plotted and studied. An optimum incident angle of 80° and a defect layer thickness of 5 μm are found. The relationship between the defect mode's wavelength and the concentration of SARS‐CoV‐2 is investigated and a sensitivity of 2648.3 nm RIU−1 is attained.

Development of a Low-Shrinkage-Lightweight Engineered Cementitious Composite Based on Heavily Doped Zeolites

In recent years, there has been a growing utilization of lightweight engineered cementitious composites (LECC) for the reinforcement and restoration of contemporary building structures. This study focuses on the incorporation of zeolite, serving as an internal reservoir for moisture maintenance, and examines its impact on various performance indicators, including apparent density, compressive strength, tensile strength, and autogenous shrinkage. Additionally, the influence of zeolite on the tensile and ductile properties of LECC is elucidated with the aid of scanning electron microscopy (SEM). The findings reveal that the addition of zeolite enables the preservation of excellent mechanical properties of LECC while further reducing its density. Notably, the introduction of a substantial amount of zeolite leads to a decrease in matrix density, average crack width, and ultimate tensile strain. The ultimate tensile strain exceeds 8% to reach 8.1%, while the decrease in compressive and tensile strengths is marginal. Zeolite’s internal curing capability facilitates the complete hydration of unhydrated cement, concurrently alleviating the autogenous shrinkage of LECC. Consequently, the durability and reliability of the material are enhanced. The ability of zeolite, with its porous framework structure, to significantly improve the ultimate tensile strain of the matrix can be attributed to the amplified occurrence of active defects and a shift in the pull-out mode of PE fibers from “pull-out” to “pull-through”. This study presents a promising alternative material in the field of engineering, holding potential for diverse building and infrastructure projects, as it enhances their durability and reliability.

Microstructure and properties of TiC–Ti5Si3 reinforced copper matrix composites

In this study, Ti5Si3 single-phase and TiC–Ti5Si3 hybrid phases reinforced copper matrix composites with different volume fractions were prepared by melt reaction. The microstructures and mechanical properties of the composites were analyzed to investigate their wear and tensile mechanisms. The wear resistance of the composite materials exhibits a non-linear behavior with increasing load, initially decreasing and then increasing, reaching its lowest point at 7.35 N. At higher loads, such as 9.8 N, the composites form a more stable and effective wear-resistant layer, exhibiting the positive impact of the reinforcing phase on wear resistance. Furthermore, as the content of the reinforcing phase increases, the brittleness of Ti5Si3 also increases, along with the expansion of the interface between the reinforcing phase and the matrix. This results in a transition of the wear mechanism from delamination wear to abrasive wear and an increased likelihood of spalling under shear forces. Therefore, the composite material achieves optimal wear resistance when the Si content is at 1%. In addition, the TiC and Ti5Si3 phases within the Cu matrix not only effectively bear the load but also impede crack propagation, resulting in a shift in the fracture mode of the composites from ductile fracture to cleavage fracture or quasi-cleavage fracture as the reinforcement content increases. Finally, hot rolling proves to be an effective method for refining the reinforcement and improving its uniformity, leading to significant enhancements in tensile strength and ductility. However, the reinforcement causes a disruption in the continuity of the matrix, resulting in a reduced elongation in the composite material with a Si content of 1% after the hot rolling process.

Terahertz absorber with switchable functionality from ultra-broadband to broadband

In this paper, we present a terahertz absorber with switchable absorption modes by utilizing patterned graphene‑vanadium dioxide. Through thermal tuning of vanadium dioxide and electrical control of graphene, our device demonstrates two distinct absorption modes that can be switched between. By maintaining the Fermi energy of graphene at 1 eV, the device achieved an ultra-broadband absorption with a bandwidth of 4.62 THz, spanning from 3.58 to 8.20 THz, when the conductivity of vanadium dioxide reached 200,000 S/m. Once the conductivity dropped to 200 S/m, we observed a narrower bandwidth of 0.95 THz (ranging from 6.58 to 7.53 THz) for the broadband absorption. At this stage, manipulating the Fermi energy of graphene allows for control over the amplitude and frequency shift of the broadband mode. Additionally, the device benefits from a remarkable degree of symmetry, which guarantees its insensitivity to changes in polarization angle. The impact of geometric parameters on the robustness of absorption characteristics is also discussed. The device may have potential applications in broadband mirror and electromagnetic shielding and so on.