Flight of an aeroplane with solid-state propulsion
采用固体推进系统的飞机
▲ 作者：Haofeng Xu、Yiou He、Kieran L. Strobel、Christopher K. Gilmore、Steven R. H. Barrett，et al
▲ 链接：
https://www.nature.com/articles/s41586-018-0707-9
▲ 摘要：
本论文描述了一架采用固体推进系统的小型飞机的飞行，这使得制造更安静、机械更简单且不产生燃烧排放的飞机成为可能。
一直以来，飞行器的动力来自带有活动部件的发动机，例如推进器或涡轮机，并且通常依靠化石燃料燃烧。有人提出采用电空气动力学装置——通过电力加速流体中的离子以形成离子风产生推力，可作为推进飞行器的一种替代方法。
研究人员设计了一架带有电空气动力推进系统的小型固定翼飞机，并进行了试飞。该飞机重2.45千克，翼展5米，依靠定制系统提供动力。定制动力系统包含一个电池组和高压电源转换器，输出功率约500瓦。
在10次试飞中，飞机在室内空间成功飞行了60米，平均飞行高度为0.47米。尽管整体效率较低，但是其推功比与传统推进系统（如喷气发动机）相当。
这种特殊的飞机设计优先考虑的是小机型而不是高效率，但未来的设计可以提高效率。
▲ Abstract
Since the first aeroplane flight more than 100 years ago, aeroplanes have been propelled using moving surfaces such as propellers and turbines. Most have been powered by fossil-fuel combustion. Electroaerodynamics, in which electrical forcesaccelerate ions in a fluid, has been proposed as an alternative method of propellingaeroplanes—without moving parts, nearly silently and without combustionemissions. However, no aeroplane with such a solid-state propulsion system has yet flown. Here we demonstrate that a solid-state propulsion system can sustain powered flight, by designing and flying an electroaerodynamically propelledheavier-than-air aeroplane. We flew a fixed-wing aeroplane with a five-metrewingspan ten times and showed that it achieved steady-level flight. All batteries and power systems, including a specifically developed ultralight high-voltage (40-kilovolt) power converter, were carriedon-board. We show that conventionally accepted limitations in thrust-to-power ratio and thrust density, which were previously thought to make electroaerodynamics unfeasible as a method ofaeroplane propulsion, are surmountable. We provide a proof of concept forelectroaerodynamic aeroplane propulsion, opening up possibilities for aircraft and aerodynamic devices that are quieter, mechanically simpler and do not emit combustion emissions.
地球科学Geoscience
Twentieth-century contribution to sea-level rise from uncharted glaciers
20世纪海平面上升“贡献者”包括未知冰川
▲ 作者：David Parkes、Ben Marzeion
▲ 链接：
https://www.nature.com/articles/s41586-018-0687-9
▲ 摘要：
20世纪全球平均海平面上升（GMSLR）主要是由冰川和冰盖的质量损失、海水的热膨胀和陆地蓄水能力的变化引起的。
然而，无论是基于观测还是气候模型结果，这些贡献的估计总和往往低于观测到的GMSLR。
这里，研究人员发现从1901年到2015年，错漏和消失的冰川产生了大约16.7到48.0毫米的海平面当量（SLE）。
其中，缺失的冰川是那些人们期望今天仍存在的小冰川，但由于区域分析和理论比例关系，这些冰川并没有反映在冰川数据库中，而它们大约贡献了12.3到42.7毫米的历史SLE。
此外，消失的冰川（1901年存在，但到2015年已经融化的冰川，因此也不在数据库单中）估计贡献了4.4到5.3毫米。
▲ Abstract
Global-mean sea-level rise (GMSLR) during the twentieth century was primarily caused by glacier and ice-sheet mass loss, thermal expansion of ocean water and changes in terrestrial water storage. Whether based on observations or results of climate models, however, the sum of estimates of each of these contributions tends to fall short of the observed GMSLR. Current estimates of the glacier contribution to GMSLR rely on the analysis of glacier inventory data, which are known to undersample the smallest glacier size classes. Here we show that from 1901 to 2015, missing and disappeared glaciers produced a sea-level equivalent (SLE) of approximately16.7 to 48.0 millimetres. Missing glaciers are those small glaciers thatwe expect to exist today, owing to regional analyses and theoretical scaling relationships, but that are not represented in the inventories. These glaciers contributed approximately 12.3 to 42.7 millimetres to the historical SLE.Additionally, disappeared glaciers (those that existed in 1901 but had melted away by 2015, and that therefore cannot be included in modern global glacier inventories) made an estimated contribution of between 4.4 and 5.3 millimetres. Failure to consider these uncharted glaciers may be an important cause of difficulties in closing the GMSLR budget during the twentieth century: their contribution is on average between 0.17 and 0.53 millimetres of SLE per year, compared to a budget discrepancy of about 0.5millimetres of GMSLR per year between 1901 and 1990. Although the uncharted glaciers will have a minimal role in sea-level rise in the future, and are less important after 1990, these findings imply that undiscovered physical processes are not required to close the historical sea-level budget.
生物学Biology
Improved reference genome of Aedes aegypti informs arbovirus vector control
改良埃及伊蚊基因组助力虫媒控制研究
