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To obtain high energy and power densities of planar MSCs, a large number of nanostructured materials including activated carbon, [10,11] carbon nanotube, [12][13][14] graphene, [15][16][17] metal oxide, [18][19][20] conductive polymer, [21,22] and their composites [23,24] have been used to construct MSCs. Those with superior volumetric capacitance and power performance are desired.In recent years, electrode engineering approaches to improve the performance of MSCs have also been reported. [25][26][27][28][29][30] A narrow interspace between interdigital electrodes reduces the distance of ions diffusion and the equivalent series resistance of electrodes, leading to improved capacitance and power density of MSCs. [31] The interspace width is dependent on the preparation technologies. Specifically, for current screen printing [26] and inkjet printing, [32,33] the interspace width is over 40 µm. Photolithography technology has achieved an interspace width of 15 µm. [3,34,35] High-precision 3D printing [36,37] and electro-deposition [38,39] have attained an interspace width of 120 and 5 µm, respectively. Laser-based technology having advantages of flexible machining and precise patterning without additional assistance of templates or masks, [40] can accomplish the one-step fabrication of MSCs with interdigital electrodes. [41][42][43] The pioneering work was from Gogotsi group, which reported the preparation of MXene MSCs The capacitance of microsupercapacitors (MSCs) can double if both sides of substrates are used to construct MSCs. Nevertheless, achieving electric connections of MSCs through substrates is a challenge due to the difficulty in precisely positioning each MSC couple that has two of the same MSCs units on two sides. In this work, taking advantage of the synchronous etching on both sides of transparent polyethylene terephthalate substrates by femtosecond laser pulses, a double-sided configuration is attained with high precision in the alignment of back-to-back MSC couples and versatile doubleside MSCs are realized via arbitrary on-and through-substrate connections of MXene MSC units. The MXene double-side MSC fabricated by the series connection of 12 spiral pattern MXene MSC units with interdigital electrodes of 10 μm width interspace can output a large working voltage of 7.2 V. Additionally, femtosecond laser etching brings the transformation of MXene into titania near-etched edges with a lateral distance less than 1 µm. Such a small laser-affected area has little influence on the capacitive performance, which is one of advantages for femtosecond laser over conventional lasers. This research is valuable for one-step manufacturing of highly integrated MSCs in the field of miniaturized energy storage systems.

The time of arrival (ToA) and received signal strength (RSS) estimation errors are modelled based on channel measurements in a non-line-of-sight indoor environment. It is found interesting that their errors are largely independent. Suboptimal hybrid ToA/RSS ranging estimators are derived in closed form based on the obtained error models, and shown to achieve near-optimal performance. The performance of all the estimators improves as the bandwidth increases.Introduction: State-of-the-art ranging systems exploit the time of arrival (ToA) or the received signal strength (RSS) of wireless signals [1]. Owing to the weak direct path and rich scattering, it is a challenging task to design and evaluate the performance of indoor ranging systems under non-line-of-sight (NLoS) scenarios. To the best of our knowledge, ToA and RSS error models have been studied separately [2, 3], but never jointly, through real-world measurement under NLoS scenarios.In this Letter, we study the ToA-and/or RSS-based ranging performance in a typical NLoS indoor environment, under the OFDM system assumption. Our main contributions are: (i) a channel measurement campaign, taking both the ToA-and the RSS-based ranging into account, was carried out in the indoor environment; (ii) the ToA and the RSS estimation errors are modelled into functions of the bandwidth based on the measurement; (iii) suboptimal hybrid ToA/RSS ranging estimators are derived in closed form and shown to achieve near-optimal performance, especially when the bandwidth is large.

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Usually, the surface quality of components produced under turning of particle reinforced metal matrix composites (PRMMCs) is one of the most important factors influencing their practical performance. Keeping good surface quality needs additional manufacturing cost or loss of productivity. In this study, semi-finish turning tests were conducted using high-power diode laser and cemented carbide tools to evaluate the superiority of the laser-assisted machining of PRMMCs and better understand its governing mechanism. The Taguchi method is used to optimize the cutting parameters in laser-assisted machining (LAM) by seeking the smallest surface roughness and the best signal-to-noise ratio. The results of orthogonal experiment revealed that the most significant turning parameter for surface roughness was feed rate, followed by the rotational speed, the cutting temperature, and the depth of cut. LAM provides a larger material removal rates under the same surface roughness compared with conventional machining. The tool wear mechanism for coated and uncoated cemented carbide tools was evaluated, and the LAM provides a maximum 2.31 times improvement in cemented carbide tools over conventional machining. Additionally, an economic analysis reveals significant benefits of diode laserassisted machining of PRMMCs over conventional machining with conventional carbide tools.

The exploration of colossal dielectric permittivity (CP) materials with low dielectric loss in a wide range of frequencies/temperatures continues to attract considerable interest. In this paper, we report CP in (Al + Nb) co-doped rutile SnO2 ceramics with a low dielectric loss at room temperature. Al0.02Nb0.05Sn0.93O2 and Al0.03Nb0.05Sn0.92O2 ceramics exhibit high relative dielectric permittivities (above 103) and low dielectric losses (0.015 < tan δ < 0.1) in a wide range of frequencies and at temperatures from 140 to 400 K. Al doping can effectively modulate the dielectric behavior by increasing the grain and grain boundary resistances. The large differences in the resistance and conductive activation energy of the grains and grain boundaries suggest that the CP in co-doped SnO2 ceramics can be attributed to the internal barrier layer capacitor effect.