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71.
Soumitra Sengupta 《Pramana》1999,53(6):1115-1119
In a space-time with torsion, the action for the gravitational field can be extended with a parity-violating piece. We show
how to obtain such a piece from geometry itself, by suitably modifying the affine connection so as to include a pseudo-tensorial
part. A consistent method is thus suggested for incorporating parity-violation in the Lagrangians of all matter fields with
spin in a space-time background with torsion. 相似文献
72.
Alleviating hysteresis and improving device stability of perovskite solar cells via alternate voltage sweeps 下载免费PDF全文
The anomalous hysteresis in a perovskite solar cell induced by an asymmetric field is confirmed by a capacitance–voltage measurement. By applying several cycles of alternating reverse and forward scans, this hysteresis phenomenon is obviously alleviated, resulting in a hysteresis-less state in the perovskite solar cell. Meanwhile, the open-circuit voltage and power conversion efficiency of the perovskite solar cell are enhanced by 55.74% and 61.30%, respectively, while the current density and fill factor keep almost invariable. The operation of alleviating hysteresis is essential for further research and is likely to bring in performance gains. 相似文献
73.
The degradation of transconductance (G) of gate-modulated generation current IGD in LDD nMOSFET is investigated. The G curve shifts rightward under the single electron-injection-stress (EIS). The trapped electrons located in the gate oxide over the LDD region (QL) makes the effective drain voltage minish. Accordingly, the G peak in depletion (GMD) and that in weak inversion (GMW) decrease. It is found that Δ GMD and Δ GMW each have a linear relationship with the n-th power of stress time (tn) in dual-log coordinate: Δ GMD ∝ tn, Δ GMD ∝ tn (n=0.25). During the alternate stress, the injected holes neutralize QL induced by the previous EIS. This neutralization makes the effective VD restore to the initial value and then the IGD peak recovers completely. Yet the threshold voltage recovery is incomplete due to the trapped electron located over the channel (QC). As a result, GMW only recovers to the circa 50% of the initial value after the hole-injection-stress (HIS). Instead, GMD is almost recovered. The relevant mechanisms are given in detail. 相似文献
74.
开发实践表明,聚合物驱采用单一段塞注入方式,暴露出了易发生剖面返转的问题。鉴于此,研究了通过交替注入方式改善吸液剖面的新型驱油方法。应用渗流力学基本定律,结合实验数据,论证了单一段塞注入剖面返转及交替注入抑制剖面返转的力学机制。结果表明,注聚合物过程中高、低渗层阻力系数表现规律不同,而交替注入方式能够使高、低渗层阻力系数表现规律趋同,是单一段塞注入方式发生剖面返转、交替注入方式抑制剖面返转的根本原因。本文建立了用低、高渗层累积阻力系数的比值作为吸液剖面改善效果的评价方法,该比值越小,低渗层吸液比例越高,吸液剖面改善效果越好。 相似文献
75.
Alternate oscillations of self-terminating and recombination lasers in univalent calcium and strontium ions 下载免费PDF全文
The univalent calcium and strontium ions have been confirmed as ideal lasing substances both for self-terminating laser and recombination laser by theoretically analysing their energy level structures and lasing mechanisms. With the optimization of the excitation circuit and the improvement of the laser cavity as well as the laser discharge tube, thealternate laser oscillatlons of the two laser mechanisms were suceessfully realized by longitudinal pulsed discharge in mixture vapours of helium and univalent ions of calcium or strontium, respectively. The dependences of laser performance on working parameters, together with the characteristics of the photoelectric pulse waveforms were elementally studied and analysed. 相似文献