High-speed Devices Research Articles

Machine learning and deep learning in project analytics: methods, applications and research trends

Project analytics refers to applying analytical techniques and methods to past and present data to gain insights into how the underlying project is performing. Machine learning (ML) and Deep learning (DL) have acquired extensive usage in various disciplines due to their analytical strength and the availability of high-speed computational devices. This article comprehensively surveys commonly used ML and DL algorithms for addressing project-related research problems. This study used author-selected keywords from article metadata to construct, analyse and visualise keyword co-occurrence networks to explore research trends. It has several notable observations: (a) Support vector machine and Random forest are the most used ML algorithms in project analytics; (b) although Artificial neural network remains a frequently used DL algorithm, its project-related applications have recently experienced a substantial decrease; (c) genetic algorithm and Fuzzy logic are the other advanced analytical methods frequently coined with ML and DL algorithms for addressing project-related problems; (d) there is a sharp increase of ML and DL applications in various project contexts; and (e) researchers used ML and DL algorithms for studying cost and time performance in construction and software project contexts. This article details these observations further and discusses their novelty and implications for research and practice.

Graphene Devices for Aerial Wireless Communications at THz

This paper investigates the state-of-the-art of graphene-based technologies for the prospective use cases of end-to-end terahertz (THz) communication systems, such as industrial Internet of Things (IoT) applications and unmanned aerial vehicles (UAVs). THz communications offer ultra-high throughput and enhanced sensing capabilities, enabling advanced applications like UAV swarms and integrated sensing, localization, and mapping. The potential of wireless THz communication can be unlocked by graphene technology. Graphene, owing to its remarkable electrical, thermal, and mechanical properties, emerges as a promising candidate for a multitude of applications in aerial wireless communications in the THz band, including high-speed electronic devices, tunable metamaterials, and innovative antennas. However, reliable tools for the simulation-based design of graphene components, able to account for the fabrication-related uncertainties, are still missing. This paper presents the envisaged possibilities of wireless communications in THz bands, overviews graphene devices for RF applications at THz, and discusses the open issues of modelling THz devices and THz channel.

Field-free spin–orbit torque switching in ferromagnetic trilayers at sub-ns timescales

Current-induced spin torques enable the electrical control of the magnetization with low energy consumption. Conventional magnetic random access memory (MRAM) devices rely on spin-transfer torque (STT), this however limits MRAM applications because of the nanoseconds incubation delay and associated endurance issues. A potential alternative to STT is spin-orbit torque (SOT). However, for practical, high-speed SOT devices, it must satisfy three conditions simultaneously, i.e., field-free switching at short current pulses, short incubation delay, and low switching current. Here, we demonstrate field-free SOT switching at sub-ns timescales in a CoFeB/Ti/CoFeB ferromagnetic trilayer, which satisfies all three conditions. In this trilayer, the bottom magnetic layer or its interface generates spin currents with polarizations in both in-plane and out-of-plane components. The in-plane component reduces the incubation time, while the out-of-plane component realizes field-free switching at a low current. Our results offer a field-free SOT solution for energy-efficient scalable MRAM applications.

Annihilation mechanisms for interacting skyrmions in magnetic nanowire

Abstract Magnetic skyrmions are considered potential candidates for spintronics-based memory and logic devices. For achieving high-density and high-speed devices, it is essential to study their interactions. In this paper, the interaction, dynamics, and annihilation mechanisms of Néel skyrmions in nanowire confinement under the influence of spin-transfer torque (STT) and edge forces have been studied. Initially isolated, two Néel skyrmions are brought into proximity, leading to distinct interaction scenarios characterized by varying current densities. We explore the impact of these interactions on skyrmion trajectories, size evolution, and annihilation phenomena. Our findings reveal the interplay of skyrmion-skyrmion repulsive forces, edge effects, and the influence of STT, shedding light on the rich dynamics of these topological magnetic textures. Furthermore, we unveil the distinct annihilation mechanisms of the leading and trailing skyrmions under different forces, providing valuable insights into the fundamental physics of skyrmion behavior in confined geometries.

Low-Temperature Growth of InGaAs Quantum Wells Using Migration-Enhanced Epitaxy.

The growth of InGaAs quantum wells (QWs) epitaxially on InP substrates is of great interest due to their wide application in optoelectronic devices. However, conventional molecular beam epitaxy requires substrate temperatures between 400 and 500 °C, which can lead to disorder scattering, dopant diffusion, and interface roughening, adversely affecting device performance. Lower growth temperatures enable the fabrication of high-speed optoelectronic devices by increasing arsenic antisite defects and reducing carrier lifetimes. This work investigates the low-temperature epitaxial growth of InAs/GaAs short-period superlattices as an ordered replacement for InGaAs quantum wells, using migration-enhanced epitaxy (MEE) with low growth temperatures down to 200-250 °C. The InAs/GaAs multi-quantum wells with InAlAs barriers using MEE grown at 230 °C show good single crystals with sharp interfaces, without mismatch dislocations found. The Raman results reveal that the MEE mode enables the growth of (InAs)4(GaAs)3/InAlAs QWs with excellent periodicity, effectively reducing alloy scattering. The room temperature (RT) photoluminescence (PL) measurement shows the strong PL responses with narrow peaks, revealing the good quality of the MEE-grown QWs. The RT electron mobility of the sample grown in low-temperature MEE mode is as high as 2100 cm2/V∗s. In addition, the photoexcited band-edge carrier lifetime was about 3.3 ps at RT. The high-quality superlattices obtained confirm MEE's effectiveness for enabling advanced III-V device structures at reduced temperatures. This promises improved performance for applications in areas such as high-speed transistors, terahertz imaging, and optical communications.

Thermal Protection of Piezoelectric Actuators Using Complex Electrical Power Measurements and Simplified Thermal Models

This article describes a method for estimating the temperature of high-power piezoelectric actuators when a direct temperature measurement is impractical. The heat flow is estimated from the real component of the electrical power; then, the temperature is estimated by a transfer function that approximates the thermal response of the system. The transfer function can be derived analytically from a lumped-element approximation or calibrated experimentally by using a system identification method. The proposed method is demonstrated on a piezoelectric stack actuator used in a high-speed nanopositioning device. A second-order transfer function estimates the temperature to within 3 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula> C of a reference measurement for a range of operating conditions. The proposed method is suitable for protecting piezoelectric actuators in applications where direct temperature measurement is impractical, for example, due to space or wiring constraints.

Damping and Interfacial Dzyaloshinskii-Moriya Interaction in Thulium Iron Garnet/Bismuth-Substituted Yttrium Iron Garnet Bilayers.

Thin films of ferrimagnetic iron garnets can exhibit useful magnetic properties, including perpendicular magnetic anisotropy (PMA) and high domain wall velocities. In particular, bismuth-substituted yttrium iron garnet (BiYIG) films grown on garnet substrates have a low Gilbert damping but zero Dzyaloshinskii-Moriya interaction (DMI), whereas thulium iron garnet (TmIG) films have higher damping but a nonzero DMI. We report the damping and DMI of thulium-substituted BiYIG (BiYTmIG) and TmIG|BiYIG bilayer thin films deposited on (111) substituted gadolinium gallium garnet and neodymium gallium garnet (NGG) substrates. The films are epitaxial and exhibit PMA. BiYIG|TmIG bilayers have a damping value that is an order of magnitude lower than that of TmIG, and BiYIG|TmIG|NGG have DMI of 0.0145 ± 0.0011 mJ/m2, similar to that of TmIG|NGG. The bilayer therefore provides a combination of DMI and moderate damping, useful for the development of high-speed spin orbit torque-driven devices.

Tailoring the linear and nonlinear optical properties of PVC/PE blend polymer by insertion the spindle copper nanoparticles

PVC/PE polymer nanocomposites were synthesized with 0–3 wt% copper (Cu) nanoparticles via melt extrusion. XRD analysis showed characteristic peaks corresponding to crystalline PVC, PE, and Cu phases. FTIR confirmed the presence of signature vibrational modes of PVC and PE. Optical studies revealed tunable light absorption, refractive index, dielectric response, and bandgap by tailoring copper content. The composites displayed enhanced linear and nonlinear optical susceptibilities, with potential applications in photonics. Optical absorption studies revealed a redshift in bandgap from 3.38 eV to 2.19 eV as Cu concentration increased from 0 to 3%, indicating enhanced visible light absorption. The real dielectric constant rose from 1.3527 to 1.4578 at 190 nm wavelength when Cu content was raised from 0 to 3%. Imaginary dielectric constant exhibited a stepwise enhancement from 2.43 × 10−3 to 3.97 × 10−3 at 190 nm with increasing Cu loading up to 3 %. The nonlinear refractive index varied from 1.2 × 10−8 cm2/W to 2.1 × 10−8 cm2/W across 500–900 nm wavelengths for 0–3% Cu. Meanwhile, the dispersion parameters including, the single oscillator energy (Eo) and the dispersion energy (Ed) were extracted. The relaxation time of the studied samples were extracted, which decreased after the insertion the nanofillers. The outcomes revealed that Cu nanoparticles' doped films favor a high-speed optoelectronic device more than the pristine film.The results demonstrate tunable optical and dielectric characteristics, underscoring the potential of Cu-based PVC/PE nanocomposites.

Low voltage-driven, high-performance TiO2 thin film transistors with MHz switching speed.

High-speed circuits based on thin film transistors (TFTs) show promising potential applications in biomedical imaging and human-machine interactions. One of the critical requirements for high-speed electronic devices lies in high-frequency switching or amplification at low voltages, typically driven by batteries (∼3.0 V). To date, however, most electrical performances of metal oxide TFTs are measured under direct current (DC) conditions, and their dynamic switching behaviour is scarcely explored and studied systematically. Here in this work, we present low voltage-driven, high-performance TiO2 thin film transistors, which can be operated at a switching speed of MHz. Our proposed TiO2 TFTs demonstrated a high on-off ratio of 107, together with a subthreshold swing (SS) of ∼150 mV Dec-1 averaged over four orders of magnitude, which can be further reduced below 100 mV Dec-1 when the temperature cools to 77 K. Additionally, the TiO2 TFTs exhibit excellent gate-pulse switching at various frequencies ranging from 1.0 Hz to 1.0 MHz. We also explored the potential application of the TiO2 TFTs as logic gates by constructing a resistive-loaded inverter, which shows stable operation at 10 kHz frequency and various temperatures. Thus, our results show the great potential of TiO2 TFTs as a new platform for high-speed electronic applications.

Snapshot compressive structured illumination microscopy.

We propose a snapshot compressive structured illumination microscopy (SoSIM) system to increase the number of reconstructed resolution-enhanced (RE) images per second and reduce the data bandwidth by capturing compressed measurements. In this system, multiple low-resolution images are encoded by a high-speed digital micro-mirror device with random binary masks. These images are then captured by a low-speed camera as a snapshot compressed measurement. Following this, we adopt an efficient deep neural network to reconstruct nine images with different structured illumination patterns from a single measurement. The reconstructed images are then combined into a single-frame RE image using the method of spectral synthesis in the frequency domain. When the camera operates at 100 frames per second (fps), we can eventually recover dynamic RE videos at the same speed with 100 fps.

High-speed optical 3D measurement device for quality control of aircraft rivet

High-speed optical 3D measurement device for quality control of aircraft rivet

高速穴施肥装置设计与试验

In order to improve the adaptability of the fertilizer point-applied device to the working speed, the key components of the high-speed fertilizer point-applied device were designed and simulated by numerical calculation in this study. The effects of working speed, discharging height and discharging mass on the distribution length of fertilizer particles were analyzed by a one-factor test, and a suitable range of factors was determined. The Box-Behnken test was conducted to investigate the interaction effect of the three factors on the distribution length of fertilizer particles, and the quadratic regression was fitted to the test results to establish the regression equations of working speed, discharging height and discharging mass on the distribution length of fertilizer particles, and the optimal combinations of the parameters of working speed, discharging height and discharging mass were obtained by solving the equations. Finally, the reliability and authenticity of the simulation analysis were verified by bench test.

O-Shape Fractal Antenna Optimized Design with Broad Bandwidth and High Gain for 6G Mobile Communication Devices

Optimization of antenna parameters is important for achieving the best design that has higher results for gain and bandwidth while also having a smaller size. One such antenna design is numerically investigated and presented in this research. The antenna is optimized to an O-shape fractal design from a square patch design. The antenna is created by etching a slot of a square patch and making an O-shape fractal metamaterial patch antenna that operates on the THz band. The THz patch antenna is also investigated for its metamaterial properties. The optimization of the THz patch antenna is carried out for substrate height, slot length, and slot width. The optimized design has a size of 65 × 65 µm2. The highest bandwidth of 31.4 THz (138%) and the highest gain of 11.1 dBi is achieved. The optimized design is then investigated for multiple elements. The two-element MIMO antenna design using an O-shape patch is investigated to observe its performance and compare it with an O-shape single-element design. The two-element MIMO antenna design gives two bands with a bandwidth of 18 THz (113%) and 21 THz (56%). The gain of this design is 5.18 dBi and the size is 130 × 65 µm2. A comparison between the O-shape single-element fractal design, two-element fractal MIMO design, and other published designs is carried out. The compact, broadband, and high gain design presented can be used for 6G high-speed mobile communication devices.

Direct growth of lattice mismatched InP on GaAs substrate with AlAs/GaAs superlattice-induced lateral quasi-quantum-wire buffer

With the technological importance, the demand on the infrared photonic and high-speed electronic devices is increasing in line with the needs for InP substrate which is used for the platform to grow the device structure. However, the InP substrate is not only limited to small diameter but also has poor mechanical hardness which are the bottleneck in reducing the device fabrication cost. In this regard, various methods are proposed to obtain InP template which grown on cheap and robust substrates as an alternative to replace the native InP substrate. In this article, we report an InP layer directly grown on GaAs substrate with the help of AlAs/GaAs superlattice-induced lateral quasi-quantum-wire buffer. The InP layer exhibited enhanced material quality with low defect density as a result of strain relaxation induced by the lateral quasi-quantum wires. This result can give insight into the alternative route to create large and robust InP template for low cost InP-based device applications.

Internet of Things Based Reconfigurable SIMD Processor for High-Speed End Devices in FPGA

Internet of Things Based Reconfigurable SIMD Processor for High-Speed End Devices in FPGA

Controlling the 2D Magnetism of CrBr3 by van der Waals Stacking Engineering.

The manipulation of two-dimensional (2D) magnetic order is of significant importance to facilitate future 2D magnets for low-power and high-speed spintronic devices. van der Waals stacking engineering makes promises for controllable magnetism via interlayer magnetic coupling. However, directly examining the stacking order changes accompanying magnetic order transitions at the atomic scale and preparing device-ready 2D magnets with controllable magnetic orders remain elusive. Here, we demonstrate the effective control of interlayer stacking in exfoliated CrBr3 via thermally assisted strain engineering. The stable interlayer ferromagnetic (FM), antiferromagnetic (AFM), and FM-AFM coexistent ground states confirmed by the magnetic circular dichroism measurements are realized. Combined with the first-principles calculations, the atomically resolved imaging technique reveals the correlation between magnetic order and interlayer stacking order in CrBr3 flakes unambiguously. A tunable exchange bias effect is obtained in the mixed phase of FM and AFM states. This work will introduce new magnetic properties by controlling the stacking order and sequence of 2D magnets, providing ample opportunities for their application in spintronic devices.

Application of High-Speed Gallium Nitride Devices in Mass Spectrometry Sweeping Mode

Quadrupole mass spectrometers are widely used, and voltage scanning is their traditional working mode. By fixing the scanning voltage frequency and changing the value of the RF voltage, ions with different mass numbers can reach the detector in sequence, achieving ion selection. When analyzing high-mass molecules, several kilovolts of scanning voltage are required, which is not conducive to the miniaturization and safety of the instrument. By selecting the frequency of the scanning RF power supply and fixing the value of the RF power supply voltage, ion selection can be achieved by changing the frequency of the RF power supply, enabling miniaturized mass spectrometry analysis of high-mass molecules. In this paper, a high-speed gallium nitride driver circuit for frequency scanning mass spectrometry analysis is designed. The NCP51820 high-speed gate driver and INN650D140A gallium nitride MOS tube are selected to form a full-bridge driver, realizing a quadrupole rectangular wave RF power supply. The system has a maximum withstand voltage of 650 V and a frequency range of 400 K–4 MHz, allowing for scanning measurements of mass numbers ranging from 3 to 606 amu.

Reversible Ultrafast Chiroptical Responses in Planar Plasmonic Nano-Oligomer.

Ultracompact chiral plasmonic nanostructures with unique chiral light-matter interactions are vital for future photonic technologies. However, previous studies are limited to reporting their steady-state performance, presenting a fundamental obstacle to the development of high-speed optical devices with polarization sensitivity. Here, a comprehensive analysis of ultrafast chiroptical response of chiral gold nano-oligomers using time-resolved polarimetric measurements is provided. Significant differences are observed in terms of the absorption intensity, thus hot electron generation, and hot carrier decay time upon polarized photopumping, which are explained by a phenomenological model of the helicity-resolved optical transitions. Moreover, the chiroptical signal is switchable by reversing the direction of the pump pulse, demonstrating the versatile modulation of polarization selection in a single device. The results offer fundamental insights into the helicity-resolved optical transitions in photoexcited chiral plasmonics and can facilitate the development of high-speed polarization-sensitive flat optics with potential applications in nanophotonics and quantum optics.

Test on adsorption posture and seeding performance of the high-speed precision dual-chamber maize metering device based on the seed characteristics

This study introduced a high-speed precision dual-chamber maize seed metering device and examined the impact of irregular-shaped holes on the planting quality in order to enhance the precision of maize planting. Based on the characteristic dimensions of maize seeds, the horizontal-profiled seed metering plates, lateral-profiled seed metering plates, vertical-profiled seed metering plates, and round-hole seed metering plates were developed. This research examined how the performance of individual seed metering plate types is affected by varying forward velocity and negative pressure conditions. Utilizing high-speed camera technology, statistical analysis was conducted on the adsorption posture data of maize seeds with different hole shapes. It was found that the qualified index showed a positive correlation with the quantity of seeds in the horizontal posture, while the quantity of seeds in the lateral posture and vertical postures collectively influenced the multiples index and the miss index. This research explored the optimal operating parameters for the high-speed precision dual-chamber maize seed metering device, with a forward velocity of 15 km/h and a negative pressure of 14 kPa. The validation tests yielded the qualified index of 98.13 %, the multiples index of 1.19 %, and the miss index of 0.68 %. This study offers insight for developing different seed metering devices based on seed characteristic dimensions, while also offers insights into the mechanism for improving the seeding quality of high-speed precision seed metering devices.

Terahertz spin currents resolved with nanometer spatial resolution

The development of coherent terahertz (THz) spin currents with femtosecond temporal resolution has been extensively studied due to its significant implications for advancing high-speed information processing devices. However, the precise spatial resolution of THz spin currents, which is crucial for increasing storage density, is still unknown. In this study, we employ spintronic THz emission nanoscopy (STEN) to achieve efficient injection and accurate detection of femtosecond THz spin currents with nanoscale lateral spatial resolution (∼60 nm). The occurrence of emission signals at the fifth harmonic order indicates a substantial signal-to-noise ratio. Additionally, STEN proves to be an effective method for characterizing and etching nanoscale spintronic heterostructures. The integration of nanophotonics, nanospintronics, and THz-nanotechnology into a unified platform is poised to enable the characterization of spin states at micro-to-nanoscale densities, accelerate the development of high-frequency spintronic optoelectronic nanodevices, and catalyze other revolutionary technical applications.