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The overall objective of the Small Business Research Program is to develop a reliable high quality Bi-2212 powder suitable for demonstration scale (> 1km lengths) multifilamentary round wires for magnets with fields above 15 T. For heat treating long length of wires, cables and magnets (or coils), the processing window needs to be increased. In an attempt to increase J_E and the processing heat treatment window of multifilamentary Bi-2212/Ag wires the impact of secondary phase (AEC) is investigated. During Phase I, the primary emphasis was given to produce powders with well dispersed (14,24)AEC particles. Two approaches were investigated. Optimization of processing parameter during Phase I resulted in a Bi-2212 with well dispersed AEC particles. DTA studies reveal that the solidification behavior changes with increasing amount of AEC phase. Two powder made with composition (~Bi2212 with 1 wt% AEC) was down selected and shipped to B-OST for wire fabrication. Multifilamentary Bi-2212/Ag with configuration 55 x18 are fabricated to diameter 0.8 mm-1.2 mm. The filaments are found to be uniform with no significant filament merging showing good powder homogeneity. The performance of the wires is comparable to the Nexan Benchmark used at B-OST. Wires are also OP processed at NHMFL. A JE (4.2 K,5 T) of 853 A/mm² and 1022 A/mm² was observed in the wires PMM190422 and PMM190518 wires respectively. The wires are treated with standard processing parameters used in OP processing. Further heat treatment optimization work is in progress. The Phase I results demonstrate the potential of the approach; however, further refinement is needed to realize the overall goal of the program which will be done in Phase II. During Phase II, the composition (amount of secondary phases) required to improve processing (heat treatment) window and JE at high magnetic fields in Bi-2212/Ag multifilamentary wires will be optimized. The heat treatment conditions to further refined to reduce size (primary particle size) of the AEC particles used as seeds in processing approach 1. The heat treatment equipment, including the mantle structure to minimize any possibility of contamination of powder in the furnace during heat treating will also be developed. Heat treatment conditions of the Bi-2212/Ag wires will be optimized to maximize the potential of the approach

This paper proposes a sequential convex optimization method to solve broader classes of optimal power flow (OPF) problems over radial networks. The non-convex branch power flow equation is decomposed as a second-order cone inequality and a non-convex constraint involving the difference of two convex functions. Provided with an initial solution offered by an inexact second-order cone programming relaxation model, this approach solves a sequence of convexified penalization problems, where concave terms are approximated by linear functions and updated in each iteration. It could recover a feasible power flow solution, which usually appears to be very close, if not equal, to the global optimal one. Two variations of the OPF problem, in which non-cost related objectives are optimized subject to power flow constraints and the convex relaxation is generally inexact, are elaborated in detail. One is the maximum loadability problem, which is formulated as a special OPF problem that seeks the maximal distance to the boundary of power flow insolvability. The proposed method is shown to outperform commercial nonlinear solvers in terms of robustness and efficiency. The other is the bi-objective OPF problem. A non-parametric scalarization model is suggested, and is further reformulated as an extended OPF problem by convexifying the objective function. It provides a single trade-off solution without any subjective preference. The proposed computation framework also helps retrieve the Pareto front of the bi-objective OPF via the e-constraint method or the normal boundary intersection method. This paper also discusses extensions for OPF problems over meshed networks based on the semidefinite programming relaxation method.

We report the optimized performance of two advanced CO₂ capture processes is compared to that of a monoethanolamine (MEA) baseline for a gas-powered CO₂ capture retrofit of an existing coal-fired facility. The advanced temperature-swing processes utilize piperazine and mixed-salt solvents. The mixed-salt treatment involves the use of ammonia for CO₂ absorption and potassium carbonate primarily to control ammonia slip. The processes are represented in terms of energy duty requirements within a modular heat integration code developed for CO₂ capture modeling and optimization. The model includes a baseload coal plant, a gas-fired subsystem containing gas turbines and a heat recovery steam generator (HRSG), and a CO₂ capture facility. A formal bi-objective optimization procedure is applied to determine the design (e.g., detailed HRSG components and pressure levels, gas turbine capacity, CO₂ capture capacity) and time-varying operations of the facility to simultaneously maximize net present value (NPV) and minimize total capital requirement (TCR), while meeting a maximum CO₂ emission intensity constraint. For a realistic scenario constructed using historical data, optimization results indicate that both advanced processes outperform MEA in both objectives, and the mixed-salt process in turn outperforms the piperazine process. Specifically, for the scenario considered, the base case mixed-salt process achieves 16% greater NPV and 14% lower TCR than the MEA process, and 10% greater NPV and 5% lower TCR than the piperazine process. A five-case sensitivity study of the mixed-salt process indicates that it is competitive with the piperazine process and consistently outperforms the MEA process.