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991.
Weixing Wan M. L. Parkinson P. L. Dyson A. M. Breed R. J. Morris 《Journal of Atmospheric and Solar》1999,61(18):1353
The influence of the interplanetary magnetic field (IMF) on the occurrence of sporadic E (Es)-layers in the southern polar cap ionosphere has been investigated. We statistically analysed ionogram and Doppler velocity observations made using a HF digital ionosonde located at Casey, Antarctica (66.3°S, 110.5°E; 81°S magnetic latitude) during the two summer campaign intervals 1 January to 18 February, and 1 November to 31 December 1997. The ionogram and Doppler velocity measurements were used to determine the Es-occurrence and electric field vectors (assuming E×B/B2 drift), respectively. Concurrent IMF data were obtained from measurements made on board the Wind spacecraft. First, the gross properties of the IMF dependence of Es-formation were obtained: the occurrence rate was higher for negative By and/or positive Bz, and lower for positive By and/or negative Bz. To reconcile these gross properties with the electric field theory of Es-layer formation, the detailed diurnal variation of both Es-occurrence and the ionospheric electric field were obtained for different orientations of the IMF. The main statistical results are that: (1) the By component mainly controls the occurrence of the midnight Es-layers through its influence on the corresponding South West electric field; and (2) the Bz component mainly controls the occurrence of the evening Es-layers. However, the change in the occurrence rate for evening Es-layers was not related to the strength of the associated North West and North East electric fields. The total occurrence of Es-layers depended more on By than on Bz, owing to the dominance of By-controlled midnight Es-layers in the occurrence distribution. Nevertheless, the dependence of Es-occurrence on Bz was important. We suggest that the increase in Es-occurrence for positive Bz might be explained by the intermittent production of lower F-region ionisation by polar showers and squalls, which also increase in frequency and intensity for positive Bz. The importance of metallic ion transport within the ionosphere is also considered. 相似文献
992.
多线程技术在伽玛全谱仪软件系统中的应用 总被引:5,自引:2,他引:3
介绍了采用多线程实现的CD-10型野外伽玛全谱仪的软件系统,以串口这时通讯为例,说明多线程的使用方法及程步骤。 相似文献
993.
994.
湘西浅变质岩系中钨锑金矿床成矿系列 总被引:9,自引:1,他引:8
湖南西部钨锑金矿床主要集中分布于雪峰弧形构造带内,赋存于元古宇浅变质岩系中,严格受断裂构造控制。矿种组合为一组具有成因联系的W-Sb-Au,Sb-Au,W-Au和Au、Sb等矿床成矿系列。各矿床具有相似的区域构造-地球化学环境、形成规律及成因机制。在元古宇浅变质岩系中控矿构造系统发育的区(带)是金矿有利的远景区(带)。 相似文献
995.
996.
997.
城市空气质量周报及其进展 总被引:9,自引:0,他引:9
城市空气质量周报是国家环境保护总局深化空气污染防治工作的新举措, 它的公布有利于对政府的环保工作力度和成效以及生产激动经营者的环境行为实施公众监督;有利于调动公众参与污染防治工作的积极性; 有利于提高全民环境意识, 进而提高国家和民族的整体文明程度; 有利于推动我国环保工作与国际接轨, 树立我国在国际社会中的可持续发展形象。但周报仅仅是日报和预报的基础, 随着环境保护力度的加大和环境监测技术的发展, 空气质量日报和空气污染预测预报也将逐步向公众公布 相似文献
998.
不同地质雷达测量参数对数据采集效果的影响 总被引:4,自引:0,他引:4
地质雷达探测技术是近年来适应快速、准确、无损的探测地下障碍物及对地下工程质量评价而迅速发展的方法技术。而这门方法的一个根本环节就是数据采集。本文通过结合工程实例来探讨不同的地质雷达测量参数对数据采集效果的影响。 相似文献
999.
Shunguo Yan Changgui Wan Ronald E. Sosebee David B. Wester Ernest B. Fish Richard E. Zartman 《Journal of Arid Environments》2000,46(4):397
Responses of photosynthesis (Pn), stomatal conductance (gs), pre-dawn leaf water potential (Ψlp) and leaf water content (ωl) of creosote bush to 10 rainfall events in the Chihuahuan Desert were investigated. Infiltration of rainwater was manipulated by applying municipal biosolids. The responses of Pnand water relation parameters to rainfall (>10 mm) were mainly dependent upon drought severity: (1) following a moderate drought, Pn, gs, Ψlpand ωlrecovered to corresponding values of irrigated plants within 2 days after a 23-mm rainfall; (2) Ψlpand gsresponded to a 15-mm rainfall within 2 days, following a 25-day drought, whereas responses of Pnand ωlwere delayed for several days; (3) responses of Pn, gs, Ψlpand ωlto a 14·7-mm rainfall were all delayed for several weeks following a 110-day drought, but the delay was longer in Pn, gsand ωlthan in Ψlp. Creosote bush responded to small rainfall events (approximately 6 to 8 mm) with an increase in Ψlp, but without noticeable changes in gsand Pn, suggesting a strong stomatal control of water loss even though xylem embolism was reduced. Biosolids applied at high rates (3·4 and 9 kgm−2) decreased the soil water by 2 to 4 mm following rainfall events, and this in turn delayed and decreased the responses of Pnand water relation parameters to rainfall.Pnand gswere linearly related to ωland exponentially related to Ψlp. With the generally coincidental responses of Pnor gsand ωlto rainfall, we concluded that the responses of Pnand gsto rainfall were dependent on leaf rehydration which resulted from restored hydraulic conductance following drought. 相似文献
1000.
黄鳍刺(鱼叚)虎鱼(Acanthogobius flavimanu)前期幼鱼摄食习性和摄食率的初步研究 总被引:1,自引:0,他引:1
对 1997年 5月莱州湾潍河口采集的黄鳍刺虎鱼前期幼鱼进行消化道内含物分析。结果表明黄鳍刺虎鱼前期幼鱼为浮游动物食性 ,主要摄食镖蚤类、短尾类幼体、猛蚤类和甲壳类的六肢幼体。摄食有明显的节律 ,清晨消化道内含物最多 ,傍晚最少。摄食的种类随昼夜不同时间有一定的变化。摄食率 :C=9.2 52 8g/ (10 0 g· BW· d) ;日摄食量 :FD=0 .0 0 4 7g/ d。 相似文献