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阐述了在GPS精度鉴定系统中,针对短基线快速检核GPS接收机内部噪声水平测试方法进行研究,并结合试验验证了方法的可靠性. 相似文献
174.
甚宽频带地震计频域标定的噪声数据处理方法 总被引:2,自引:3,他引:2
周云耀 《大地测量与地球动力学》2004,24(1):121-126
分析了频域标定中的噪声及传统数据处理方法,提出数据处理的本质是噪声处理的观点,探讨了不同噪声的不同处理方法,详细研究了长周期非线性漂移的噪声处理方法,有效地提高了频域标定精度。 相似文献
175.
An improved quantum secure direct communication (QSDC) protocol is proposed in this paper. Blocks of entangled photon pairs are transmitted in two steps in which secret messages are transmitted directly. The single logical qubits and unitary operations under decoherence free subspaces are presented and the generalized Bell states are constructed which are immune to the collective noise. Two steps of qubit transmission are used in this protocol to guarantee the security of communication. The security of the protocol against various attacks are discussed. 相似文献
176.
Hanne H. Christiansen Ole Bennike Jens Bcher Bo Elberling Ole Humlum Bjarne H. Jakobsen 《第四纪科学杂志》2002,17(2):145-160
Terraces of different age in the Zackenberg delta, located at 74°N in northeast Greenland, have provided the opportunity for an interdisciplinary approach to the investigation of Holocene glacial, periglacial, pedological, biological and archaeological conditions that existed during and after delta deposition. The raised Zackenberg delta accumulated mainly during the Holocene Climatic Optimum, starting slightly prior to 9500 cal. yr BP (30 m a.s.l.) and continued until at least 6300 cal. yr BP (0.5 m a.s.l.). Evidence of sea‐level change is based on conventional 14C dates of shells from the marine delta bottomsets, 14C AMS dating of macroscopic plant material from the foresets and of fluvial deposits. Arthropod and plant remains from 7960 cal. yr BP in the delta foresets include the oldest evidence of the arctic hare in Greenland and evidence of a rich herb flora slightly different from the modern flora. Empetrum nigrum and Salix herbacea remains indicate a summer temperature at least as high as today during delta deposition. Post‐depositional nivation activity, dated by luminescence, lichenometry and Schmidt Hammer measurements indicate mainly late Holocene activity, at least since 2900 yr BP, including Little Ice Age (LIA) avalanche activity. Pedological analyses of fossil podsols in the Zackenberg delta, including 14C AMS dating of selected organic rich B‐horizons, show continued podsol development during the Holocene Climatic Optimum and into the subsequent colder period of the late Holocene, until 3000–2400 yr BP. A Neo‐Eskimo house ruin found on the lower part of the delta, presently being eroded by the sea, is dated to AD 1800. It presumably was abandoned prior to AD 1869, and suggests that some of the last Eskimos that lived in northeast Greenland might have occupied the Zackenberg delta. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
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E. Castellano S. Becagli J. Jouzel A. Migliori M. Severi J. P. Steffensen R. Traversi R. Udisti 《Global and Planetary Change》2004,42(1-4):195
The sulphate glacio-chemical profiles constitute a reliable proxy marker for reconstruction of past volcanic history, assuming a reliable method to distinguish sulphate spikes and to evaluate the flux of individual events is set up. The resulting volcanic event profile is used to reconstruct past event frequencies, and to investigate possible links between volcanism and climatic changes. Volcanic event signatures are useful also in comparing time scales from ice cores drilled at different locations. In this paper, a new method to pick out volcanic signals is proposed. It improves on methods based on the calculation of a threshold using a general mean value plus a multiple of the standard deviation by adding: (1) quantification of nonvolcanic sulphate contributions; (2) sulphate fluxes, instead of concentrations, accounting for accumulation rate changes; (3) data treatment using a log-normal statistic, instead of a Gaussian-type distribution, to take into account the real sulphate distribution; (4) a smoothed curve (weighted fitting) to better understand the residual variability of the sulphate background.This method is used to detect volcanic events throughout the 45 ky time span of the EDC96 ice core, drilled at Dome C on the East Antarctic plateau. A total of 283 volcanic signatures are recovered, with a mean of 6.3 events per millennium. The temporal event frequencies indicate that the last 2000 years were probably characterized by the highest volcanic activity in the period covered by the core and that there is no clear link between number of events recorded and climatic changes. 相似文献
179.
基于深度学习的地震数据噪声压制方法是当前地震数据去噪处理的重要方向。深度学习方法突破了传统滤波处理的局限,在对常规地震数据的噪声压制中表现出效率高、信噪分离效果好的特点。但针对深部弱有效反射数据,当前的深度学习方法特征提取能力有限,难以取得较好的去噪效果。笔者等结合深反射地震数据特点,针对当前深度学习噪声压制方法在特征提取及对数据集依赖上的局限,提出了基于注意力循环生成对抗网络(Attention Cycle- Consistent Generative Adversarial Networks,A- CGAN)的深反射地震数据随机噪声压制方法。借助循环一致生成对抗网络(Cycle- Consistent Generative Adversarial Networks,Cycle- GAN)的域映射思想,降低对数据集的要求。为了构建适用于深反射地震数据的去噪网络,从3个方面对Cycle- GAN进行改进:在Cycle- GAN的生成器(去噪器)中加入残差结构和注意力机制,用于加深网络深度和提高其特征提取能力;在Cycle- GAN的鉴别器中使用块判决,提高鉴别精度和准确度;在损失函数部分加入感知一致性损失函数,提升网络模型恢复纹理细节信息的能力。通过合成地震数据和实际深反射地震数据测试,验证了优化算法的有效性,体现了良好的应用价值。 相似文献
180.
六盘山盆地被巨厚的黄土所覆盖,是表层和深层双复杂区域。巨厚的黄土和复杂的地形条件使该区干扰波非常发育,严重影响了地震资料的信噪比。为了有效调查该区干扰波发育特征,并进行针对性地压制,通过盒子波调查技术在该区的应用分析,提出了和生产结合进行盒子波调查的有效方式,克服了静校正问题对盒子波调查数据的影响。针对两种地形条件下的盒子波资料,分析了在不同地形和表层条件下干扰波场的变化,认为影响浅层和中深层信噪比的干扰波特征存在差异;并通过组合压噪效果分析,提出对不同深度勘探目标进行针对性压噪的组合接收方式,提高了六盘山地区巨厚黄土塬勘探区目标层采集资料的信噪比。 相似文献