Electromagnetic interference has been a major concern, especially in health-related matters, industrial pollution, and military functions. In this study, our main purpose is to develop a flexible, lightweight, and high-performance material with high effectiveness for electromagnetic interference (EMI) shielding. We have developed thin films of pure Mxene, as well as heterogeneous layered structures of MWCNTs@MoS2/Mxene. The EMI shielding effectiveness of 1mg MWCNTs@MoS2 and 3mg of MWCNTs@MoS2 are determined as 50 to 60 dB in X band (8.2 to 12.4 GHz), which is better than the pure Mxene. Although by increasing the composition of CNT@MoS2 more, the EMI shielding performance decreases, the heterogeneous films exhibit unprecedented flexibility and durability, thus rendering them with the potential application.
In this preliminary study, polyamide (PA12) based nanocomposites reinforced with different concentrations of multi-walled carbon nanotubes (MWCNTs) were synthesized by using SLS. Initially, printing parameters of SLS were optimized to print the pure and nanocomposites samples. Then printed samples were examined for mechanical and piezoresistive response to evaluate the effect of addition of MWCNTs in the polymer matrix. The nanocomposites samples showed reduction in mechanical properties which might be attributed to change in the interfacial bonding between filler and the matrix as compared to pure PA samples. Microscopic and thermal characterization are required to figure out the cause of reduction in the mechanical properties which is a future work. In terms of piezoresistivity, the sample with lowest concentration of MWCNTs showed highest gauge factor/ sensitivity. The final aim of this study is to fabricate the nanocomposites that can be used in self-sensing applications in the form of strain sensing devices.
As Gulf Cooperating Council countries integrate more renewables into their energy mix, energy system planning becomes increasingly important for technology selection and evaluation. This paper presents a preliminary modeling investigation of the impact of increasing shares of solar power in future electricity sectors on primary energy consumption, environmental emissions and production-demand matching. The results indicate significant seasonal overproduction, which will require to be addressed using appropriate measures.
The relation of the fastest explosive time scale τ e(0) that characterizes the initiation of a homogenous, isochoric autoignition process with the ignition delay time t ign is explored. This investigation is carried-out for six fuels at 0.5 ≤ φ ≤ 4.0, p(0)=2, 10, 20 atm and T (0)= 900, 1100, and 1350 K. It is shown that the variation of τ e(0)/t ign is small in the cases of hydrogen and methanol, in all cases considered. However, the variation of this ratio is significant for methane and n-heptane for most of the cases considered. For iso-butanol, the variation is relatively small, except the cases when T (0) = 1350 K. Finally, for DME, the variation of τ e(0)/t ign is relatively small.
Heated and unheated flows with forced convection over two fixed circular cylinders in tandem are studied numerically for 80≤Re≤250 and 1≤T^*≤2.3. Three different spacing ratios (L/D)=[2,4,8] are considered under three heating conditions. The scenarios considered are (1) heated upstream and unheated downstream cylinders, (2) unheated upstream and heated downstream cylinders and (3) heated upstream and downstream cylinders. These scenarios represent the limiting case for a cross-flow heat exchanger, where the downstream tubes are at increasingly lower or higher temperature for cooling or heating, respectively. The global aerodynamic forces on the cylinder as vortices shed was investigated. The flow is visualized by plotting the streamlines, temperature fields, and velocity magnitude contours for the different spacing ratios and compared to the flow regimes in literature namely, Extended-body, Reattachment, and Co-shedding regimes. The surface heat transfer coefficients are analyzed for different scenarios.
The influence of streamwise oscillations on the lift and drag coefficients over isothermal and non-isothermal circular cylinder is numerically studied in this work. Temperature difference of 300, 600, and 900 K is used between the cylinder wall and the incoming fluid flow at Reynolds number of 100. Air is used as the fluid and the temperature dependent properties of air are used for the analysis. Numerical simulation is done on Ansys/fluent with O-type structured mesh. The vibration of the circular cylinder is induced via user defined function at a frequency ratio of 0.5, 1, and 2, with the natural frequency of the cylinder being 2.5 Hz marking its Strouhal number of 0.167.
Large Break Loss-of-Coolant-Accident (LBLOCA) in a Zion-like plant was simulated using the MAAP code. The plant responses during the accident were investigated for conventional Zr cladding and two ATF cladding materials, SiC and FeCrAl. The maximum cladding temperature increase was delayed by replacing Zr with SiC or FeCrAl, which is considered to be due to smaller oxidation energies of the two ATF cladding materials. The gap pressure causing tube burst was increased at slower rates with SiC and FeCrAl, indicating that tube burst can be delayed as well. The tube burst behavior of the materials will be studied at the next stage.
As technological advancements occur in the field of manufacturing, 3D printing has been increasingly growing and becoming more attractive to manufacturers. Additive manufacturing (AM) has enabled the manufacturing of intricate shapes and geometries which cant be done using traditional fabrication processes [1]-[7]. Using this technology, rapid prototyping has received more interest as it has become more accessible and feasible. AM technologies has enabled the manufacturing of parts in plastics, ceramics, and metals which makes it a very versatile process. Despite having a lot of work done on the pros and cons of AM, there still is a need to further clarify. This study will focus on metal additive manufacturing technologies to compare advantages and disadvantages of different metal AM technologies. Comparing the advantages and disadvantages of these processes will enable the designer or operator pick the most suitable manufacturing process for the specific use.
Fossil fuels will continue to play an important role for the forthcoming decades, particularly in certain hard-to-abate transport and industrial sectors. Unconventional oil has emerged as a sizeable contributor to meeting the global energy demand in the energy transition period. However, unfavorable economic conditions compounded by the Covid-19 pandemic have intensified uncertainties regarding their future prospects. This paper explores prospects and challenges faced by unconventional oil resources in the post Covid-19 near- to long-term. Based on recent projections, unconventional oil resources, although significantly affected by the pandemic in the short term, could however reach approximately 30% share of oil production by the early to the mid 2030's.
The influence of topology hybridization on the compressive properties of the mathematically-known triply periodic minimal surface (TPMS) lattice was studied in this paper. The diamond (D) and F-Rhombic Dodecahedral (FRD) lattice structures comprising each of 8 cells were considered. The sandwiched geometries were numerically subjected to a quasi-static compressive force until densification was reached. The energy absorbed and the metamaterial's ultimate strength was estimated. The results revealed that by hybridizing the D lattice with the FRD structure, the specific energy absorbed and ultimate strength of the D lattice were improved.
