Triggered-lightning properties inferred from measured currents and very close electric fields

Triggered-lightning properties, including dart-leader charge density, return-stroke propagation speed, dart-leader electric potential, dart-leader propagation speed, and dart-leader current, inferred from return-stroke current and very close electric field measurements, are presented. Although most of the estimates are based on relatively crude models, they are all generally in good agreement with independent measurements and/or theoretical considerations found in the literature. The results are likely to be applicable to subsequent strokes in natural lightning.     

多回击负地闪先导通道的辐射和光学特征

利用闪电VHF窄带干涉仪辐射源定位系统和高速摄像系统,对青海大通地区一次有5次回击的负地闪放电过程进行了同步观测,对比分析了通道传输过程的辐射和光学特征.结果表明,光学通道亮度能补充VHF干涉仪定位先导通道的电流特征,VHF干涉仪定位弥补了光学设备拍摄弱放电和云内流光通道的不足;在通道分枝结构上,干涉仪定位的通道和光学通道呈现出很好对应.干涉仪定位分枝通道的辐射源点较明显,但分枝光学通道的出现明显落后于干涉仪定位辐射源通道.对用两种不同观测手段探测的先导通道进行速度计算,发现两者计算的直窜先导和直窜梯级先导速度量级一致,均为106m·s-1,但干涉仪在时间的获取及精确量化上有优势,干涉仪定位计算先导速度的精确度高于光学通道定位.     

Observation and study on the whole process of cloud-to-ground lightning using narrowband radio interferometer

A narrowband radio interferometer has been developed and used to locate the entire sources of VHF radiations from a negative cloud-to-ground (CG) lightning discharge which contains 19 strokes. This system uses five antennas to form an array consisting of short- and long-baselines along two or- thogonal directions. The system error which comes from frequency conversion is reduced by phase detection through direct high frequency amplifying. An interactive graphic analysis procedure is used to remove the fringe ambiguities which exist inherently in interferometry and to determine the direction of lightning radiation sources in two dimensions (azimuth and elevation) as a function of time at a time resolution of microsecond orders. With the developed system, the whole progression process in time and space of a lightning flash can be reconstructed. In this paper, combining the synchronous data of electric filed change and VHF radiation, the whole processes of an example negative CG flash have been studied in detail. It is found that the preliminary breakdown event of the CG flash started from negative charge region and exhibited firstly a downward pregression and then an upward propagation. There were very intense and continuous radiations during stepped leaders which became much stronger when the first return stroke began. In contrast, there were less and only discrete radiations during dart leaders. Stepped leader and dart leader may transform to each other depending on the state of the ionization of the path. The progression speed of initial stepped leaders was about 105 ms?1, while that was about 4.1×106 and 6.0×106 ms?1 for dart leaders and dart-stepped leaders, respectively. M events produced hook-shaped field changes accompanied by active burst of radiations at their begin- nings. Followed these active radiation processes, M events appeared to contact finally into conducting main discharge channels. The mean progression speed of M events was about 7×107 ms?1, greater than that of the dart leaders and dart-step leaders. K events and attempted leaders were essentially the same as dart leaders except that they could not reach the ground and initiate return strokes.     

Simultaneous optical and electrical observations on the initial processes of altitude-triggered negative lightning

Using a high-speed camera system and two electric field antenna systems, we have documented the initial processes of an altitude-triggered negative lightning (ATNL). The optical records clearly show that ATNL begins with the inception and propagation of an upward positive leader (UPL) and then a simultaneous propagation of UPL and downward negative leader (DNL), known as the bidirectional leader process, follows. Based on the optical records, it is inferred that (1) the triggering height is about 371 m; (2) the two-dimensional (2D) propagation speed of the UPL in its inception phase is about 3.8–5.5 × 10⁴ m s^− 1 during its propagation from about 393 to 452 m above the ground; (3) the grey levels of the DNL are about one order of magnitude higher than that of the UPL in their inception phase; (4) a discharge phenomenon propagating along the elevated triggering wire part of the lightning channel occurs after the mini-return stroke (MRS), with a 2D propagation speed of about 1.6–2.0 × 10⁵ m s^− 1. Combined with the simultaneous electric field change records, it is further inferred that (1) the UPL incepts about 932 μs earlier than the unstable DNL and about 4.1 ms earlier than the stable DNL; (2) the unstable DNL propagates downward intermittently three times with a time interval of about 1 ms, and each propagation contains a different number of steps with an average step length of about 7 m; (3) the stable DNL incepts at the tip of the unstable one, with a 2D propagation speed of about 1.9 × 10⁵ m s^− 1, an average step length of about 3 m, and a stepping time interval varying from 6 to 31 µs with a mean value of 15 µs.     

计算机I／O端口病毒的诊断与消除

计算机 I/O 端口病毒破坏并行口和 RS232串行口,致使打印机无法工作,双机通讯无法进行。本文据处理邯郸台网286微机 I/O 端口病毒的实践,剖析了该病毒的机理,提供了快速诊断和消除该病毒的方法,对于保障台网特别是华北遥测台网联网系统的正常运行具有实用意义。     

Observations on the leader-return stroke of cloud-to-ground lightning with the broadband interferometer

Radio frequency observations of cloud-to-ground lightning (CG) were made in 1999 in Guangdong Province with the broadband lightning interferometer. In this paper, radiation source locations and electric field waveforms are analyzed for different types of breakdown events, including the preliminary breakdown of in-cloud activities, the stepped leaders of initial strokes to ground and activities during and following return strokes. It is shown that the structure and development of lightning discharges and associated breakdown processes can be reconstructed by using this new type of lightning radiation source location system. The detectable radiation of lightning was primarily produced by the negative breakdown process. The channel was concentrated with few branches during the preliminary breakdown stage of CG lightning flashes. The radiation sources appeared generally at the tip of the channel. During the late period of the stepped leader, the radiation sources were dispersed with branches extended away from the main channel. The radiation sources were in a certain length segment of the channel and the altitude of the segment descended along with the propagation of the leader to the ground. During the preliminary breakdown and the stepped leader of initial strokes to the ground, a sequence of fast negative streamers were observed to start continually from or farther away the lightning-initiated region and propagate along the developed leader channel, which may supply negative charge that assisted the leader’s development. The progression speed of fast negative streamers was about ten times faster than the average speed of lightning channel.     

A review of ten years of triggered-lightning experiments at Camp Blanding, Florida

The principal results of triggered-lightning experiments conducted at the International Center for Lightning Research and Testing (ICLRT) at Camp Blanding, Florida, from 1993 through 2002 are reviewed. These results include (a) characterization of the close lightning electromagnetic environment, (b) first lightning return-stroke speed profiles within 400 m of ground, (c) new insights into the mechanism of the dart-stepped (and by inference stepped) leader, (d) identification of the M-component mode of charge transfer to ground, (e) first optical image of upward connecting leader in triggered-lightning strokes, (f) electric fields in the immediate vicinity of the lightning channel, (g) inferences on the interaction of lightning with ground and with grounding electrodes, (h) discovery of X-rays produced by triggered-lightning strokes, (i) new insights into the mechanism of cutoff and reestablishment of current in rocket-triggered lightning. Selected results are discussed.     

基于双幂次滑模的多机器人编队控制

本文研究了基于领航跟随法的多机器人系统编队控制问题.首先,基于队形约束,给出跟随者期望的轨迹,将编队问题转化为单个跟随者的轨迹跟踪问题.在此基础上,基于双幂次滑模趋近律,设计了跟随者的线速度和角速度控制器,保证了跟踪误差能够快速收敛到零,从而保证了编队队形的稳定.最后,通过仿真验证了所提方法的有效性.     

珠三角地区保健微博用户的空间特征及影响因素

选择以信息流通互动水平突出的新浪微博为样本获取平台,以珠三角地区保健微博用户为样本来源地,通过相关标签检索、筛选、编码获得保健资讯生产者与关注者样本。运用社会网络分析方法、空间自相关和逐步线性回归方法,对生产者之间的社会网络交互特征、关注者的空间分布格局及其影响因素进行分析。研究结论为：1）保健微博生产者之间能够构建本地社会网络,各类型间存在显著分异,但是地区差异特征较弱;2）通讯设施和地方医疗水平是保健微博关注者出现空间分异的主要因素;3）关注者的分布仍然受到地理要素的限制。     

电力工程项目管控系统之信息化——领导查询需求设计和实施

做领导查询需求难,领导也讲不清;领导查什么？表格和图表。这是本文要介绍的主要原因及内容,本人通过公司信息化建设近十年的经验,一般员工到领导的信息需求都经历过,对过程体会较深。通过下面内容的简单扼要介绍为领导查询的设计提供一些意见。