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Hard carbon (HC) materials have demonstrated great potential in sodium-ion storage; however, their application for lithium-ion storage continues to pose a challenge due to difficulties in managing carbon porosity. Most HCs exhibit completely capacitive responses when storing lithium ions, significantly hindering the nominal cell voltage of configured lithium-ion batteries. Herein, this study provides feasible solutions by introducing phenolic-formaldehyde resin-derived HCs with tunable microporous structures. The carbon porosity is well manipulated by tailoring chemically cross-linked environments via microwave-induced polymerization. A highly closed microporous HC (closed pore volume: 0.336 cm3 g−1), verified by multiple gas (N2, O2, and CO2) adsorptions, is successfully prepared by reducing the cross-linking degree. Combining in situ X-ray diffraction and ion-diffusion kinetic explorations, the linchpin has been clearly identified. Closed ultramicropores of <0.7 nm, which play the same role as the graphitic interlayer spacing in graphite, are termed as "active closed pores", because they can facilitate the insertion of lithium ions and mitigate substantial initial irreversible capacity by blocking the penetration of solvents. The HC with abundant active closed pores can deliver a reversible capacity of 550 mAh g−1 at 50 mA g−1 in 0.001–1.5 V, with an ultrahigh low-voltage plateau capacity of 230 mAh g−1 contributed by the lithium-ion insertion in active closed pores. The excellent rate capability (210 mAh g−1 at 2 A g−1) and cycling stability (90% capacity retention after 200 cycles at 0.1 A g−1) of this closed pore-rich HC are also confirmed, which is thus recognized as an ideal material for negative electrodes in lithium-ion batteries. This breakthrough discovery has enlightened the full potential of hard carbon materials for next-generation batteries. [ABSTRACT FROM AUTHOR]

This paper presents the design of a harmonic source detection system with a cascade correlation network (CCN). Current-injection-based harmonic power flow was used to calculate bus voltages and total harmonic distortion (THD). THD of voltages is used as indices for meter placement in the power network. At metering buses, it shows that the harmonic components of voltages under various loads would form particular patterns in the frequency domain, and can be used to create training examples for CCN. Good meter planning is helpful to reduce the number of meters and training examples. With an IEEE 14-bus power system, computer simulations were conducted to show the effectiveness of the proposed system. Index Terms--Cascade correlation network (CCN), harmonic source detection, total harmonic distortion (THD).