Cooperative non-orthogonal multiple access (CNOMA) has been recently adapted with energy harvesting (EH) to increase energy efficiency and extend the lifetime of energy-constrained wireless networks. In EH, two protocols are usually used for CNOMA, namely, power splitting (PS) and time switching (TS). In order to improve the existing EH protocols, this paper investigates a hybrid EH protocol-assisted CNOMA, which is a combination of the two aforementioned main existing EH protocols. The end-to-end bit error rate (BER) and outage probability (OP) expressions of users in our scheme are derived over Nakagami-m fading channels. For the sake of comparison and to highlight the achievable gains, the performance of the hybrid EH (HEH) protocol is compared with the benchmark schemes (i.e., existing EH protocols and no-EH). Based on extensive simulations, it is shown that the analytical results match perfectly with simulations which demonstrates the correctness of the derivations. Numerical results clearly indicate the superiority of the proposed scheme over all the considered benchmarks. In addition, we discuss the optimum value of EH factors to minimize the error and outage in the proposed scheme and show that an optimum value can be obtained according to channel parameters.

Here, a process for leaching vanadium from calcified roasting pellets (CPVC) of vanadium-titanium iron concentrate by a two-stage sulfuric acid cycle was proposed. When the silicon removal acid concentration of the pellet in the first stage was 1.5 mol/L, the solid-liquid ratio was 6: 1, the silicon removal acid concentration of the leaching solution was 3.0 mol/L, and the standing time was 48 h, the silica gel formation time was 23 h, the filtration time was 70 s, and the loss rates of vanadium and iron were 1.52% and 0.17%, respectively. When the acid concentration was 2 mol/L, at room temperature, using a leaching time of 28 days, and a solid-liquid ratio of 5: 1 in the second stage, the total leaching rates of vanadium and iron were 75.52% and 0.71%, respectively. The concentration of vanadium in the leaching solution reached 6.80 g/L, and vanadium was directly precipitated without extraction. After secondary roasting, the crushing strength of the pellets reached 2250 N, which met the requirement for blast furnace iron making. The Eh-pH diagrams of the V-Fe-H2O system at different temperatures were plotted. Thermodynamically, it was difficult to selectively leach vanadium and iron by changing the conventional acid leaching conditions. In addition, the pellets before and after leaching were analyzed. The grade of iron in the pellets increased slightly after leaching, and the main phases in the pellets remained as Fe2O3 and Fe9TiO15. The S in the sulfuric acid solution entered the leached pellets during the acid leaching reaction and was removed by the secondary roasting of the leached pellets.

Rare earths are classified as most important and critical material for US economy and defense by Congress and a mandate has been set to increase their in-house production, domestic resource utilization and decrease reliance on foreign resources and reserves. They are widely available in earth crust as ore (bastnaesite (La, Ce)FCO₃, monazite, (Ce, La, Y, Th)PO₄, and xenotime, YPO₄), but their so-called economic reserves are sparsely located geographically. They may be produced by various means such as beneficiation (physical, chemical, mechanical, or electrical), reduction (direct or indirect), electrolysis (of aqueous or molten / fused single or mixed salt systems) at high temperature or hydrometallurgy. Out of these, direct reduction also known as metallothermic reduction (La and Ca reduction) is mostly utilized. Its variant, high temperature electrowinning of fused salts is also practiced widely. These processes are material and application specific. In this study, author will employ thermodynamics (Ellingham diagrams, free energy of formation, reduction potential, Nernst equation, Pourbaix (E_h-pH) diagrams, E-pO^-2 diagrams), kinetics and energetic of a chemical reaction (chemical metallurgy) to reduce rare earth oxide / salt to rare earth metals (REO/RES – REM). It is shown that materials and energy requirement vary greatly depending on type of mineral ore, production facility, and beneficiation / mineral processing method selected. Aim is to reduce dependence on coal deposits. It is anticipated this route will be able to produce rare earths with > 35% yield and > 98% purity which be described in subsequent studies and patents.