Device Width Research Articles

Design and Development of a Side Spray Device for UAVs to Improve Spray Coverage in Obstacle Neighborhoods

Electric multirotor plant protection unmanned aerial vehicles (UAVs) are widely used in China for efficient and precise plant protection at low altitude for low volumes. Unstructured farmland in China has various types of obstacles, and UAVs usually use a detour path to avoid obstacles due to flight altitude limitations. However, existing UAV spray systems do not spray when in obstacle neighborhoods during obstacle avoidance, resulting in insufficient droplet coverage and reduced plant protection quality in the area. To improve the droplet coverage in obstacle neighborhoods, this article carries out a study of side spray technology with an electric quadrotor UAV, and proposes the design and development of a side spray device. The relationship between the obstacle avoidance path of the UAV and the spray pattern of the side spray device and their effect on droplet coverage in obstacle neighborhoods was explored. An accurate measurement method of the relative position between the UAV and obstacles was proposed. Spray angle calculations and nozzle selection for the side spray device were carried out in conjunction with the relative position. A rotor wind field simulation model was designed based on the lattice Boltzmann method (LBM), and the spatial layout of the side spray device on the UAV was designed based on the simulation results. To explore suitable spray patterns for the side spray device, comparative experiments of droplet coverage in obstacle neighborhoods were carried out under different environments, spray patterns, and flight parameter combinations. The relationship between the flight parameter combinations and the distribution uniformity of droplets and the effective swath width of the side spray device was explored. The experimental results were analyzed by an analysis of variance (ANOVA) and a relationship model was obtained. The results showed that the side spray device can effectively improve droplet coverage in obstacle neighborhoods compared to a device without side spray using the same flight parameter combinations. The effective swath width in obstacle neighborhoods can be increased by a minimum of 6.35%, maximum of 35.32%, and average of 15.25% using the side spray device. The error between the predicted values of the relational model and the field experiment results was less than 15%. The results verify the effectiveness and rationality of the method proposed in this article. This study can provide technical and theoretical references for improving the plant protection quality of UAVs in obstacle environments.

Characterizing parameter variations for enhanced performance and adaptability in 3 nm MBCFET technology

With the continuous scaling down of semiconductor devices, traditional transistor architectures face significant challenges in maintaining performance and power efficiency. Multi-bridge channel field-effect transistors (MBCFETs) are promising candidates for next-generation of transistors, enabling significant size reduction while preserving high performance. This paper investigates both n-type and p-type 3-nm MBCFETs with a focus on their behavior under diverse operating conditions. The study examines the influence of doping concentration, sheet thickness, temperature, device width, and the number of sheets, on the device's functionality aiming for high-performance applications. Doping concentrations of acceptors and donors ranging from 1 × 10 15 cm−3 - 9 × 10 17 cm−3 and 1 × 10 17 cm−3 - 9 × 10 19 cm−3, respectively, to observe their impact on device performance. Similarly, sheet thicknesses from 1 nm to 2 nm and device widths from 3 nm to 30 nm are analyzed to understand the scaling effects. The temperature varies from 273.15 K to 573.15 K to simulate different operational environments, while the number of sheets, ranging from 1 to 7, is adjusted to evaluate structural effects on device behavior. By extracting the subthreshold swing (SS), threshold voltage (Vth), ON-current (ION), OFF-current (IOFF), and the ION/IOFF ratio, the study offers valuable insights into the suitability and potential applications of N-MBCFET and P-MBCFET devices at the ultra-scaled 3 nm dimension. At room temperatures, the SS achieves 60 mV dec⁻1 for n-type and 64 mV dec⁻1 for p-type which indicates proper switching speed, with corresponding ON/OFF ratios of 2 × 106 and 1 × 105 for n-type and p-type, respectively. This study makes notable contributions to the field of nanoscale transistor technology, aiding in the design and optimization of future electronic devices.

Experimental demonstration of cyclotron emissions in micro-scale graphene structures

A solid-state implementation of a cyclotron radiation source consisting of arrays of semicircular geometries was designed, fabricated, and characterized on commercially available graphene on hBN substrates. Using a 10 µm design radius and device width, respectively, such devices were expected to emit a continuous band of radiation spanning from 3 to 6 GHz with a power 3.96 nW. A peak emission was detected at 4.15 GHz with an effective array gain of 22 dB. This is the first known experimental measurement of cyclotron radiation from a curved planar graphene geometry. With scaling, it may be possible achieve frequencies in the THz range with such a device.

Bulk‐Like Mott‐Transition in Ultrathin Cr‐Doped V2O3 Films and the Influence of its Variability on Scaled Devices

AbstractThe pressure‐driven Mott‐transition in Chromium doped V2O3 films is investigated by direct electrical measurements on polycrystalline films with thicknesses down to 10 nm, and doping concentrations of 2%, 5%, and 15%. A change in resistivity of nearly two orders of magnitude is found for 2% doping. A simulation model based on a scaling law description of the phase transition and percolative behavior in a resistor lattice is developed. This is used to show that despite significant deviations in the film structure from single crystals, the transition behavior is very similar. Finally, the influence of the variability between grains on the characteristics of scaled devices is investigated and found to allow for scaling down to at least 50 nm device width.

PIPE: Parallelized inference through ensembling of residual quantization expansions

Deep neural networks (DNNs) are ubiquitous in computer vision and natural language processing, but suffer from high inference cost. This problem can be addressed by quantization, which consists in converting floating point operations into a lower bit-width format. With the growing concerns on privacy rights, we focus our efforts on data-free methods. However, such techniques suffer from their lack of adaptability to the target devices, as a hardware typically only support specific bit widths. Thus, to adapt to a variety of devices, a quantization method shall be flexible enough to find good accuracy v.s. speed trade-offs for every bit width and target device. To achieve this, we propose PIPE, a quantization method that leverages residual error expansion, along with group sparsity and an ensemble approximation for better parallelization. PIPEis backed off by strong theoretical guarantees and achieves superior performance on every benchmarked application (from vision to NLP tasks), architecture (ConvNets, transformers) and bit-width (from int8 to ternary quantization).

On the insignificance of dislocations in reverse bias degradation of lateral GaN-on-Si devices

The role of threading dislocations in the intrinsic degradation of lateral GaN devices during high reverse bias stress tests (RBSTs) is largely unknown. We now present the results on lateral p-GaN/AlGaN/2DEG heterojunctions with a width of 200 μm in GaN-on-Si. A time-dependent permanent degradation of the heterojunction under high reverse bias and elevated temperatures can be observed, ultimately leading to a hard breakdown and device destruction. By using an integrated series p-GaN resistor, the device is protected from destruction and, consequently, the influence of dislocations on the degradation mechanism could be studied. Localization by emission microscopy could show that the transient current increase during a RBST is the result of the creation of a limited amount of highly localized leakage paths along the whole device width. We could establish a 1:1 correlation of leakage sites with a structural material degradation within the AlGaN barrier for nine individual positions on two different devices by planar transmission electron microscopy analysis. To unambiguously show whether dislocations in GaN-on-Si even should be considered a potential trigger for the RBST degradation in lateral heterojunctions, a combined planar and cross-sectional lamella approach was used for the first time for larger devices. This enabled the visualization of the three-dimensional propagation path of the dislocations close to the degradation sites. It was found that there is no statistically significant link between the material degradation and pre-existing dislocations. Our findings offer new insights into the GaN-on-Si material system, upon which upcoming power technologies are built upon.

Simulation and Analysis of Piezoresistive Microcantilever

Currently, most piezoresistive microcantilever sensors are configured with a dual-layer design that includes a piezoresistor integrated onto the upper surface of a microcantilever. The dual-layer design effectively enhances sensitivity and the piezoresistance effect. However, integrating the piezoresistor onto the microcantilever in the fabrication process necessitates additional steps, leading to extended manufacturing times and increased production costs. In this paper, the mechanical behavior of a single-layer piezoresistive microcantilever, namely displacement, stress, and strain, is investigated and analyzed using ANSYS Multiphysics. The contributing factors expected to affect the device's performance are its geometrical dimensions, and the materials used. Regarding the device dimensions, the length, thickness, and width of the cantilever were varied. It was found that the performance of the piezoresistive microcantilever can be improved by increasing the length and decreasing the thickness. The displacement of the microcantilevers increased by about 230%, from 75.76µm to 250.12µm, when the length was increased from 225µm to 350µm. The applied force ranged from 2uN to 12uN. Similarly, the stress and strain produced on the microcantilevers also increased by about 60.83% and 57.22%, respectively. From the material point of view, the microcantilever made with silicon always had the highest displacement value compared to silicon nitride, silicon dioxide, and polysilicon. This is due to the Young's modulus value, where materials with lower Young's modulus will have higher displacement and stress.

Small signal modulation of photonic crystal surface emitting lasers

We report the small-signal characterization of a PCSEL device, extracting damping factors and modulation efficiencies, and demonstrating -3 dB modulation bandwidths of up to 4.26 GHz. Based on modelling we show that, by reducing the device width and improving the active region design for high-speed modulation, direct modulation frequencies in excess of 50 GHz are achievable.

Approaching the Zero-Power Operating Limit in a Self-Coordinated Organic Protonic Synapse.

High-performance artificial synapse with nonvolatile memory and low power consumption is a perfect candidate for brainoid intelligence. Unfortunately, due to the energy barrier paradox between ultra-low power and nonvolatile modulation of device conductances, it is still a challenge at the moment to construct such ideal synapses. Herein, a proton-reservoir type 4,4',4″,4'''-(Porphine-5,10,15,20-tetrayl) tetrakis (benzenesulfonic acid) (TPPS) molecule and fabricated organic protonic memristors with device width of 10µm to 100nm is synthesized. The occurrence of sequential proton migration and interfacial self-coordinated doping will introduce new energy levels into the molecular bandgap, resulting in effective and nonvolatile modulation of device conductance over 64 continuous states with retention exceeding 30min. The power consumptions of modulating and reading the device conductance approach the zero-power operating limits, which range from 16.25pW to 2.06nW and 6.5fW to 0.83pW, respectively. Finally, a robust artificial synapse is successfully demonstrated, showing spiking-rate-dependent plasticity (SRDP) and spiking-timing-dependent plasticity (STDP) characteristics with ultra-low power of 0.66 to 0.82pW, as well as 100 long-term depression (LTD)/potentiation (LTP) cycles with 0.14%/0.30% weight variations.

The thickness and width of the intrinsic region effected electrical properties of GaAs p-i-n photodiodes

The thickness of the p-i-n photodiode's p and n contacts, as well as the width of the semiconductor device, affect the conductivity performance of the diode. In this study, the impact of thickness and width variations of GaAs p-i-n photodiode devices on their performance was investigated using the COMSOL Multiphysics software, which enables simulations of multiple physical fields. The terminal current and field strength at various positions were calculated for different thickness and width values. The mechanisms behind the influence of thickness and width variations on the conductivity performance were explained, and a detailed description of the distribution of terminal current and electric field magnitude was provided. Based on experimental data, the optimal thickness and width for achieving peak conductivity performance of the diode under material-saving conditions were determined, providing theoretical guidance for the preparation of efficient and stable GaAs p-i-n photodiodes.

Performance of OWC device under Stokes second-order waves

The present work simulates the flow behavior in the system having oscillating water column (OWC) device for wave energy conversion using numerical modelling. To achieve this, the OWC device is structured inside the 2-dimensional numerical wave tank (NWT). Using the ANSYS Fluent software and the multiphase-based CFD technique, the issue is resolved. Unsteady, transient, and pressure-based solvers are included in this work. In this numerical model, the governing equations are based on Reynolds Averaged Navier-Stokes (RANS) equations with the Shear Stress Transport (SST) model, to capture the turbulence effect and the interface of 2-phases are implicitly captured by using volume of fluid (VOF) method. Using an open-channel wave generator, this study generates nonlinear “second-order Stokes waves”. In addition, the impact of nonlinearity on the “free surface description” at specific locations, the vertex average of total pressure near the air-duct, and the vertex average of y-velocity through the air-duct per unit width of the OWC device are investigated in detail. The outcomes indicate that the OWC device will consistently extract energy over an extended period of time.

Investigating road conditions of crash blackspots in Addis Ababa, Ethiopia: a random parameters negative binomial model

Crash blackspots significantly impact and, to some extent, determines the entire road network’s safety level. Therefore, it is imperative to identify these blackspots and investigate the contributing factors. This becomes particularly crucial for low-income countries facing financial constraints in implementing road safety measures. Methodologically multiple studies utilised random parameter negative binomial models to predict vehicle crashes due to their ability to address unobserved heterogeneity in crash data, surpassing conventional models. However, the potential of this promising method in investigating factors influencing crash blackspots remains underutilised. This study aims to identify crash blackspots and investigates the roadway factors of such segments using the random parameters negative binomial modelling method. A three-year (2017–2019) crash data collected from the Ethiopian capital, Addis Ababa, with traffic volumes and various geometric characteristics were utilised. The model estimation results demonstrate the superiority of the random parameter negative binomial model over conventional models, showcasing its ability to reveal unobserved heterogeneity associated with road condition factors in crash blackspots. The study finds that horizontal curves and access density are significant road condition-related contributors to crash blackspots, characterised as random parameters. On the other hand, fixed-parameter influence factors include average annual daily traffic, vertical gradient, vertical curve, median width, and traffic control devices. The study highlights the need to further explore horizontal curvatures and access control as potential random parameters in crash blackspot locations. The findings may assist transportation planners/agencies in prioritising road maintenance, enhancing design standards, and implementing targeted safety interventions to improve road safety effectively.

Optimal Design of a Submerged Tidal Device for Low Current Environment

The tidal current power is one of the reliable renewable ocean energy resources that can be deployed at the region having ocean current. The feasible current speed for the application of tidal device is known to be more than 2m/s. As there are many islands in Asia where the current speed is below than the feasible speed, the submerged device that can produce the power at lower current speed with easy deployment and retrieve is introduce. To simplify the installation and O&M operations, the 4-point taut mooring system is applied that can also secure the designated position. In this study, a HAT (horizontal axis turbine) of 5-kW submerged tidal device is designed and analyzed for a low current region that consist of two buoyancy tanks, a yaw control strut, and a diffuser-type brimmed duct. To analyze the most stable condition, 9 different cases of width and height of the device and 8 different mooring arrangements (total 72 different cases) are investigated both by frequency and time domains. The results show that the dynamic behavior that mainly affects the turbine performance decreases with lower strut height. However, it was observed that the device width has little effect on the dynamic response of the device. The device dynamic motion decreases with decreasing azimuth angle and increasing hang-off angle of the mooring configuration. The optimal design configuration that can produce the maximum power is found that of 4.42 m width, 2 m height, 30° azimuth angle and 60° hang-off angle. According to API RP 2K code, the mooring system is also designed in both intact and damaged conditions. The proposed tidal device could be applied for the low current speed areas with easy implementation and maintenance.

Electrical characterization of SOI pMOS device leakage

This work investigates Silicon-on-Insulator (SOI) pMOS leakage current. Temperature measurements indicates the superposition of two leakage mechanisms: band-to-band tunneling (BTBT) and Shockley-Read-Hall Field-Enhanced (SRHFE) generation recombination. Thanks to a dedicated low current measurement setup, the impact of device width (W), thickness (tsi) and polarization (back bias, drain and source) on leakage level is evaluated for both mechanisms.

Extracting edge conduction around threshold in mesa-isolated SOI MOSFETs

This work proposes a methodology to decompose the center and edge current contributions around threshold in mesa-isolated SOI MOSFETs using 3D TCAD simulations. Applied to pMOS measurements, it reveals that the subthreshold regime is driven by the active edge, whatever the device width. It also explains why the threshold voltage modulation by the back-gate bias depends on the device width, as well as why these effects are worse for high channel doping values.

Experimental assessment of gate-induced drain leakage in SOI stacked nanowire and nanosheet nMOSFETs at high temperatures

This paper presents an experimental assessment of gate-induced drain leakage (GIDL) in stacked nanowire and nanosheet transistors for different temperatures of operation, in the temperature range between 300 K and 580 K. The temperature rise increases the GIDL current and its dependence on the device width due to the increase of band-to-band generation with temperature and weakening of electrostatic coupling.

Enhanced Mobility in Suspended Chemical Vapor-Deposited Graphene Field-Effect Devices in Ambient Conditions.

High-field-effect mobility and the two-dimensional nature of graphene films make it an interesting material for developing sensing applications with high sensitivity and low power consumption. The chemical vapor deposition process allows for producing high-quality graphene films in a scalable manner. Considering the significant impact of the underlying substrate on the graphene device performance, methods to enhance the field-effect mobility are highly desired. This work demonstrates a simplified fabrication process to develop suspended, two-terminal chemical vapor deposition (CVD) graphene devices with enhanced field-effect mobility operating at room temperature. Enhanced hole field-effect mobility of up to ∼4.8 × 104 cm2/Vs and average hole mobility >1 × 104 cm2/Vs across all of the devices is demonstrated. A gradual increase in the width of the graphene device resulted in the increase of the full width at half-maximum (FWHM) of field-effect characteristics and a decrease in the field-effect mobility. Our work presents a simplified fabrication approach to realize high-mobility suspended CVD graphene devices, beneficial for developing CVD graphene-related applications.

Temporal electron-spin splitter based on a novel semiconductor magnetic quantum microstructure with zero average magnetic fields

The dwell time is calculated for electron in a novel magnetic nanostructure with zero average magnetic fields, which is realized experimentally by constructing three nanosized ferromagnetic stripes on top and bottom of the InAs/AlxIn1-xAs heterostructure. Although structural magnetic fields are averagely equal to naught, the dwell time is still dependent on electron spins owing to the spin-field interaction. Due to the dependence of effective potential experienced by electron on structural parameters (such as magnetic strength and device width), spin-polarized dwell time can be conveniently modulated by reasonably fabricating ferromagnetic stripes. As a result, this novel magnetic microstructure can act as a temporal electron-spin splitter for spintronic device applications.

Probabilistic lateral stability and shear failure limit states of bridge natural rubber bearings

This study presents the results of a parametric analysis on a wide range of geometries of bridge natural rubber bearings for the definition of consistent limit states. This range, defined as a matrix depending on the shape factor, slenderness ratio, and device width, ensures maximum homogeneity of the studied population based on values typically found in practice for bridge applications. The effects of typical axial loads are also considered. Numerical analyses are performed on a finite element model previously developed by the authors that is capable of simulating shear failure and buckling limit states. Each specimen undergoes a numerical pushover analysis to obtain the critical shear strain and the type of ultimate limit state achieved. The results of the numerical analyses are first presented to show the influence of the investigated parameters on the type of limit state and the corresponding value of critical deformation. Design charts are constructed for practicing engineers. In addition, this work addresses the framework of performance-based design of bridges, with the objective of defining convenient damage states for the construction of bridge fragility curves. For this purpose, the statistical importance of each studied bearing pad or seismic isolator with respect to the whole population is taken into account to develop probabilistic capacity models. A slenderness threshold is validated for isolators to distinguish between potential limit states.

WEB shape modifications: angiography–histopathology correlations in rabbits

BackgroundWEB Shape Modification (WSM) over time is frequent after aneurysm treatment. In this study, we explored the relationship between histopathological changes and angiographic evolution over time in experimental aneurysms in...