Triply Periodic Minimal Surfaces (TPMS) are structures in three-dimensional space with a net zero curvature and a unique architecture that locally minimizes the area. The objective of this paper is to computationally evaluate the effective electrical and thermal conductivity of cubically symmetric TPMS solids ? namely Gyroid, IWP and Diamond over a range of relative densities using the Finite Element Method (FEM). It compares the skeletal-based cellular structures with each other and investigates the inter-relation between the skeletal and sheet networks. Results show the effective conductivity to vary linearly with increasing relative density for the three shapes, with the sheet networks demonstrating higher conductivities than the skeletal networks at all relative densities. The IWP and Gyroid exhibit similar trends while the Diamond shows a lower conductivity for the same values of relative density. Among all the structures, the IWP presented the highest value of 0.17 for the sheet network and 0.13 for the skeletal, both at a relative density of 25%.
In this paper, we experimentally investigate the compressive mechanical behavior of periodic sheet-based Gyroid graphene/PLA cellular nanocomposites at different relative densities. The Gyroid structure is a triply periodic minimal surface, in which the stress concentration is minimized. The structures are 3D printed using fused deposition modeling (FDM) technique based on graphene/PLA filaments. Scanning electron microscope (SEM) is used to assess the 3D printing quality of the fabricated samples. It is shown that the Gyroid structures have a mixed mode of deformation between stretching and bending dominated behavior making them ideal for both strong-lightweight structures and energy absorption applications.
This study investigates an extreme weather event that impacted the United Arab Emirates (UAE) in March 2016 using the Weather Research and Forecasting (WRF) model version 3.7.1 coupled with its hydrological modeling extension package (Hydro). Six-hourly forecasted forcing records at 0.5? spatial resolution, obtained from the NCEP Global Forecast System (GFS), are used to drive the three nested downscaling domains of both standalone WRF and coupled WRF/ WRF-Hydro configurations for the recent flood-triggering storm. Ground and satellite observations over the UAE are employed to validate the model results. The Pearson correlation coefficient (PCC), relative bias (rBIAS) and root-mean-square error (RMSE) are used as performance measures. Results show reductions of 24% and 13% in RMSE and rBIAS measures, respectively, in precipitation forecasts from the coupled WRF/WRF-Hydro model configuration, when compared to standalone WRF. The demonstrated improvement implies that WRF-Hydro coupling may enhance hydrologic forecasts and flash flood guidance systems in the region.
In efforts to mimic the resilience offered by natural systems, such as bone and wood, it has always been an engineering quest to create lightweight materials that exhibit high strengthto- weight ratios. In this paper, novel 3D-printed stretching-dominated micro-lattices based on mathematically-driven sheet-based triply periodic minimal surfaces (TPMS) are investigated for their mechanical properties. The TPMS-based structures allow for better efficiency dictated by topology rather than composition. The fabrication, characterization and testing of three different topologies are investigated herein; the CY, IWP and Primitive structures.
Since the World Economic Forum sets in 2004 the first Global Competitiveness Index that list countries according to several indicators, one of which is the infrastructure index, that consists of nine secondary axes, one of which is road quality index, and that the UAE is seeking to raise the standards of global competitiveness and ensure the highest levels of road safety. This research aligns with the objectives of the UAE in reducing the incidence of irrigated incidents on the network of federal roads associated with the level of lighting at night, Therefore This research examines lighting quality and its impact on car accidents at night by exploring the effects of lighting properties such as boom angle, pole height, number of luminaries, and pole arrangements on the number of night-time accidents. The case study subjects for research and analysis were selected based on a group of factors and examined using quantitative methods to enable the researcher to rank roadway improvements from most to least important. These improvements include changing the lighting systems on roadways from High-Pressure Sodium (HPS) to Light-Emitting Diodes (LEDs), a conclusion reached by studying lighting measurements and comparing them to British standards applied in infrastructure construction while considering economic and energy consumption factors. The research concludes with the optimum scenario for each proposed parameter and an advanced optimum model created after collecting all optimum scenarios of all phases.
This paper presents a novel hybrid Memristor-CMOS based flash Analog to Digital Converter (ADC). The proposed flash ADC is the first to use memristor (MR) to replace conventional resistor in order to generate different reference voltages. This is achieved by utilizing the multistate property exhibited by novel reduced Graphene oxide (rGo) MR devices fabricated and tested by our group. The electrical parameters of the devices have been extracted to develop a correlated mathematical model using the Voltage-Threshold Adaptive Model (VTEAM). Cadence circuit simulator is used to simulate the model and compare it with the experimental results. The proposed MR-based Flash ADC design solves the issue of resistor mismatch that results in encoding errors. The ability to tune the resistance value of MR post fabrication provides flexibility to modify the quantization step size. Moreover, being a nanoscale component, the usage of MR significantly improves the area efficiency of the target ADC.
Indium Selenide (InSe) has attracted significant attention due to large tunability in the band gap, high carrier mobility and unique anisotropic optical properties compared to other twodimensional (2D), graphene, based systems for chemical and gas sensing applications in the hostile environments. The expanded research requires integrating the chemical and gas sensing capability with optical sensing function. Therefore, in this work, we report the integration and characterization of this material as field-effect transistor (FET) device and as an optical sensor.
A 28GHz Doherty Power Amplifier (DPA) is implemented in 22nm FDSOI CMOS. The DPA adopts the asymmetrical topology utilizing two-stack FET amplifiers as the main and auxiliary. This allows a voltage of 2.5V aiding high output power. The integrated design implements the main and auxiliary amplifier, along with the matching and transmission line networks on chip. The simulated design exhibits a peak power gain of 9.5dB and a peak power-added efficiency 18%(PAE). Keywords?Power Amplifiers, mm-wave, Doherty, 5G.
The effectiveness of the SWJ actuator like the AFC device is the ability to provide a high oscillatory jet. For this reason, an experimental study is conducted in order to determine the jet oscillation frequency which is a crucial parameter for effective separation control. A measurement of the static pressure is made on the upper feedback channel using Kulite XTL-140 series pressure transducer for an eight different inlet mass flow rates (from 1g/s to 8 g/s). Additionally, the baseline geometry is scaled by half (2:1) and by double (1:2) and pressure measurements are also performed in these scaled geometries. The results reveal a linear trend of the oscillating frequency versus the inlet mass flow rate and the inlet Mach number for all of the geometries. Moreover, computational simulations Ansys Fluent v17.2 software have been performed for comparison and reveal a high correspondence with experimental results. The smaller geometry creates higher frequencies than the double sized geometry for the same mass flow rate.
Spacecraft?s structural integrity is the critical criteria of mission success. The majority of CubeSat?s structures are made of Aluminum alloy. It has excellent workability and availability, however; it has a low yield strength value. Nano-satellites structures must be efficiently lightweight, thermally stable and has a low rate of outgassing. Therefore, composite materials are growing exponentially in the aerospace industry. This paper proposes innovative; 3D printed composite structure. Optimized fibers orientation and material density can be precisely designed to minimize the maximum stresses experienced by the CubeSat during the rocket launch stages. Finite Element Analysis tool (ANSYS) was conducted to assess the quasi-static loads and determine the vulnerable structural areas. The detrimental critical areas were the secondary (interior rods) and tertiary (flanges and supports) parts of the satellite structure. These vulnerable areas will be precisely optimized to sustain the higher loads; hence, 3D printed. Subsequently, standardized environmental testing will be performed to validate the structural integrity and thermal compatibility to the space environment; thermal vacuum testing and vibration testing (Sine Sweep and Random vibrations).
