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Experimental Investigation of the Streamer Zone of Long-Spark Positive Leader Using High-Speed Photography and Microwave Probing 期刊论文
JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES, 2020, 125 (11)
作者:  Bogatov, N. A.;  Kostinskiy, A. Yu;  Syssoev, V. S.;  Andreev, M. G.;  Bulatov, M. U.;  Sukharevsky, D. I.;  Mareev, E. A.;  Rakov, V. A.
收藏  |  浏览/下载:21/0  |  提交时间:2020/08/18
long sparks  positive leader  streamer zone  microwave probing  high-speed photography  
Precipitation Trends Over Mainland China From 1961-2016 After Removal of Measurement Biases 期刊论文
JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES, 2020, 125 (11)
作者:  Zhang, Yingxian;  Ren, Yuyu;  Ren, Guoyu;  Wang, Guofu
收藏  |  浏览/下载:19/0  |  提交时间:2020/08/18
bias adjustment  precipitation trend  wind speed change  extreme precipitation change  
Greater flood risks in response to slowdown of tropical cyclones over the coast of China 期刊论文
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 2020, 117 (26) : 14751-14755
作者:  Lai, Yangchen;  Li, Jianfeng;  Gu, Xihui;  Chen, Yongqin David;  Kong, Dongdong;  Gan, Thian Yew;  Liu, Maofeng;  Li, Qingquan;  Wu, Guofeng
收藏  |  浏览/下载:40/0  |  提交时间:2020/06/22
tropical cyclones  translation speed  local rainfall totals  flood risks  
Toward a more effective hurricane hazard communication 期刊论文
ENVIRONMENTAL RESEARCH LETTERS, 2020, 15 (6)
作者:  Song, Jae Yeol;  Alipour, Atieh;  Moftakhari, Hamed R.;  Moradkhani, Hamid
收藏  |  浏览/下载:17/0  |  提交时间:2020/07/02
tropical cyclone  compound hazard  wind-speed  rainfall  copula  
Massively parallel coherent laser ranging using a soliton microcomb 期刊论文
NATURE, 2020, 581 (7807) : 164-+
作者:  Casanova, Emmanuelle;  Knowles, Timothy D. J.;  Bayliss, Alex;  Dunne, Julie;  Baranski, Marek Z.;  Denaire, Anthony;  Lefranc, Philippe;  di Lernia, Savino;  Roffet-Salque, Melanie;  Smyth, Jessica;  Barclay, Alistair;  Gillard, Toby;  Classen, Erich;  Coles, Bryony;  Ilett, Michael;  Jeunesse, Christian;  Krueger, Marta;  Marciniak, Arkadiusz;  Minnitt, Steve;  Rotunno, Rocco;  van de Velde, Pieter;  van Wijk, Ivo;  Cotton, Jonathan;  Daykin, Andy;  Evershed, Richard P.
收藏  |  浏览/下载:67/0  |  提交时间:2020/07/03

Coherent ranging, also known as frequency-modulated continuous-wave (FMCW) laser-based light detection and ranging (lidar)(1) is used for long-range three-dimensional distance and velocimetry in autonomous driving(2,3). FMCW lidar maps distance to frequency(4,5) using frequency-chirped waveforms and simultaneously measures the Doppler shift of the reflected laser light, similar to sonar or radar(6,7) and coherent detection prevents interference from sunlight and other lidar systems. However, coherent ranging has a lower acquisition speed and requires precisely chirped(8) and highly coherent(5) laser sources, hindering widespread use of the lidar system and impeding parallelization, compared to modern time-of-flight ranging systems that use arrays of individual lasers. Here we demonstrate a massively parallel coherent lidar scheme using an ultra-low-loss photonic chip-based soliton microcomb(9). By fast chirping of the pump laser in the soliton existence range(10) of a microcomb with amplitudes of up to several gigahertz and a sweep rate of up to ten megahertz, a rapid frequency change occurs in the underlying carrier waveform of the soliton pulse stream, but the pulse-to-pulse repetition rate of the soliton pulse stream is retained. As a result, the chirp from a single narrow-linewidth pump laser is transferred to all spectral comb teeth of the soliton at once, thus enabling parallelism in the FMCW lidar. Using this approach we generate 30 distinct channels, demonstrating both parallel distance and velocity measurements at an equivalent rate of three megapixels per second, with the potential to improve sampling rates beyond 150 megapixels per second and to increase the image refresh rate of the FMCW lidar by up to two orders of magnitude without deterioration of eye safety. This approach, when combined with photonic phase arrays(11) based on nanophotonic gratings(12), provides a technological basis for compact, massively parallel and ultrahigh-frame-rate coherent lidar systems.


  
Submicrosecond entangling gate between trapped ions via Rydberg interaction 期刊论文
NATURE, 2020, 580 (7803) : 345-+
作者:  Chatterjee, Sourav;  Guidi, Mara;  Seeberger, Peter H.;  Gilmore, Kerry
收藏  |  浏览/下载:33/0  |  提交时间:2020/07/03

Generating quantum entanglement in large systems on timescales much shorter than the coherence time is key to powerful quantum simulation and computation. Trapped ions are among the most accurately controlled and best isolated quantum systems(1) with low-error entanglement gates operated within tens of microseconds using the vibrational motion of few-ion crystals(2,3). To exceed the level of complexity tractable by classical computers the main challenge is to realize fast entanglement operations in crystals made up of many ions (large ion crystals)(4). The strong dipole-dipole interactions in polar molecule(5) and Rydberg atom(6,7) systems allow much faster entangling gates, yet stable state-independent confinement comparable with trapped ions needs to be demonstrated in these systems(8). Here we combine the benefits of these approaches: we report a two-ion entangling gate with 700-nanosecond gate time that uses the strong dipolar interaction between trapped Rydberg ions, which we use to produce a Bell state with 78 per cent fidelity. The sources of gate error are identified and a total error of less than 0.2 per cent is predicted for experimentally achievable parameters. Furthermore, we predict that residual coupling to motional modes contributes an approximate gate error of 10(-4) in a large ion crystal of 100 ions. This provides a way to speed up and scale up trapped-ion quantum computers and simulators substantially.


  
Probing the core of the strong nuclear interaction 期刊论文
NATURE, 2020, 578 (7796) : 540-+
作者:  Bialas, Allison R.;  Presumey, Jessy;  Das, Abhishek;  van der Poel, Cees E.;  Lapchak, Peter H.;  Mesin, Luka;  Victora, Gabriel;  Tsokos, George C.;  Mawrin, Christian;  Herbst, Ronald;  Carroll, Michael C.
收藏  |  浏览/下载:32/0  |  提交时间:2020/07/03

High-energy electron scattering that can isolate pairs of nucleons in high-momentum configurations reveals a transition to spin-independent scalar forces at small separation distances, supporting the use of point-like nucleon models to describe dense nuclear systems.


The strong nuclear interaction between nucleons (protons and neutrons) is the effective force that holds the atomic nucleus together. This force stems from fundamental interactions between quarks and gluons (the constituents of nucleons) that are described by the equations of quantum chromodynamics. However, as these equations cannot be solved directly, nuclear interactions are described using simplified models, which are well constrained at typical inter-nucleon distances(1-5) but not at shorter distances. This limits our ability to describe high-density nuclear matter such as that in the cores of neutron stars(6). Here we use high-energy electron scattering measurements that isolate nucleon pairs in short-distance, high-momentum configurations(7-9), accessing a kinematical regime that has not been previously explored by experiments, corresponding to relative momenta between the pair above 400 megaelectronvolts per c (c, speed of light in vacuum). As the relative momentum between two nucleons increases and their separation thereby decreases, we observe a transition from a spin-dependent tensor force to a predominantly spin-independent scalar force. These results demonstrate the usefulness of using such measurements to study the nuclear interaction at short distances and also support the use of point-like nucleon models with two- and three-body effective interactions to describe nuclear systems up to densities several times higher than the central density of the nucleus.


  
Solar wind signal in the wintertime North Atlantic oscillation and Northern Hemispheric circulation 期刊论文
INTERNATIONAL JOURNAL OF CLIMATOLOGY, 2019
作者:  Zhu, Zhipeng;  Zhou, Limin;  Zheng, Xiangmin
收藏  |  浏览/下载:46/0  |  提交时间:2020/02/17
atmospheric circulation  EP flux  NAO  solar wind speed  surface climate  
Intermittent Propagation of Upward Positive Leader Connecting a Downward Negative Leader in a Negative Cloud-to-Ground Lightning 期刊论文
JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES, 2019, 124 (24) : 13763-13776
作者:  Srivastava, Abhay;  Jiang, Rubin;  Yuan, Shanfeng;  Qie, Xiushu;  Wang, Dongfang;  Zhang, Hongbo;  Sun, Zhuling;  Liu, Minyuan
收藏  |  浏览/下载:20/0  |  提交时间:2020/02/17
positive leader  negative leader  space stem  stepped propogation  high-speed camera  
Sound Velocities in Shock-Synthesized Stishovite to 72 GPa 期刊论文
GEOPHYSICAL RESEARCH LETTERS, 2019, 46 (23) : 13695-13703
作者:  Berryman, Eleanor J.;  Winey, J. M.;  Gupta, Yogendra M.;  Duffy, Thomas S.
收藏  |  浏览/下载:14/0  |  提交时间:2020/02/17
stishovite  fused silica  shock  sound speed  melting  plate impact