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2019年长江口南北槽水域表层沉积物特征分析
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作者 刘启雄 陈家祺 +1 位作者 刘海江 张东来 《海洋工程》 CSCD 北大核心 2020年第4期100-108,共9页
为探究长江口区域最新的泥沙运动特征,于2019年枯季(1月,21个样本)和洪季(8月,58个样本)在长江口南北槽及周边区域现场取样河床表层泥沙样本,测量了样本的中值粒径和级配分布。采用Folk-Ward公式计算了泥沙样本的粒度参数(分选系数、偏... 为探究长江口区域最新的泥沙运动特征,于2019年枯季(1月,21个样本)和洪季(8月,58个样本)在长江口南北槽及周边区域现场取样河床表层泥沙样本,测量了样本的中值粒径和级配分布。采用Folk-Ward公式计算了泥沙样本的粒度参数(分选系数、偏度和峰度),并分析了沙样本内磁性物质含量。基于上述泥沙物理参数,进一步对比分析洪枯季研究区域河床表层泥沙的时空分布变化特征。分析结果表明北槽内洪枯季泥沙样本中值粒径空间分布特征一致,南槽中段洪季泥沙样本中值粒径远小于枯季泥沙样本中值粒径,南槽其他区域洪枯季泥沙样本中值粒径空间分布特征一致。同一中值粒径下,不同沙样本(中值粒径大于63μm)各粒度参数之间差异显著,而泥样本(中值粒径小于63μm)粒度参数间差异相对较小。此外,磁性物质含量测量结果表明枯季沙样本磁性物质组成的空间分布存在一定的差异,而洪季沙样本磁性物质的空间分布相对均一。 展开更多
关键词 长江口南北槽 深水航道 洪枯季 泥沙样本 中值粒径空间分布特征 粒度参数 磁性物质含量
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基于改进神经网络的图像边缘分割技术 被引量:3
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作者 卫洪春 《现代电子技术》 北大核心 2018年第16期112-115,共4页
采用梯度下降法进行图像边缘分割时受到噪声的干扰,训练过程中存在局部最佳解,从而导致图像边缘分割效果和泛化性能差。为此,提出基于改进神经网络的图像边缘分割方法,采集样本图像的中值特征量、基于梯度的特征量、Krisch算子方向特征... 采用梯度下降法进行图像边缘分割时受到噪声的干扰,训练过程中存在局部最佳解,从而导致图像边缘分割效果和泛化性能差。为此,提出基于改进神经网络的图像边缘分割方法,采集样本图像的中值特征量、基于梯度的特征量、Krisch算子方向特征量,融合三个特征向量塑造具备较强抗噪性能的样本图像特征向量,通过基于特征向量和BP神经网络的边缘检测算法,将样本图像特征向量输入四层BP神经网络,采用改进BP算法训练四层BP神经网络,采用训练后的改进神经网络完成图像边缘分割。实验结果表明,所提图像边缘分割方法细节保有性能强,分割精度和泛化能力强。 展开更多
关键词 改进神经网络 图像边缘 图像分割 梯度特征 中值特征 改进BP算法
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Capacity evaluation of the backhaul link in the outdoor relay system at 2.35GHz
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作者 张建华 Zhang Fenghua +1 位作者 Nie Xin Huang Chengxiang 《High Technology Letters》 EI CAS 2012年第4期401-405,共5页
A measurement campaign has been conducted at 2.35 GHz with a bandwidth of 50 MHz to ob- tain the statistics and evaluate the capacity of the backhaul link. Based on the measured channel im- pulse response, the channel... A measurement campaign has been conducted at 2.35 GHz with a bandwidth of 50 MHz to ob- tain the statistics and evaluate the capacity of the backhaul link. Based on the measured channel im- pulse response, the channel gain, the eigenvalue statistics and the capacity are investigated. The distribution and corresponding parameters for describing the eigenvalue dispersion, the maximum and minimum eigenvalues are given. It is found that the backhaul link is relatively stable, which shows small variance of the channel gain. In spite of the fact that there are not many scatterers in the backhaul link, the channel rank can be enhanced by using dual-polarized antennas. Thus, the backhaul link can provide enough capacity. 展开更多
关键词 relay channel measurement wideband MIMO channel channel gain eigenvaluestatistics capacity
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Zircon SHRIMP U-Pb geochronology,geochemistry and petrogenesis of the upper Eocene Shuangmaidi peraluminous granite in Baoshan Block,Western Yunnan Terrain,southwestern China 被引量:9
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作者 HUANG JingNing CHEN YongQing +3 位作者 ZHAI XiaoMing LU YingXiang XIE YongFu CHENG ZhiZhong 《Science China Earth Sciences》 SCIE EI CAS 2011年第7期982-997,共16页
The Baoshan Block is tectonically located in the middle segment of the Sibumasu plate. Granitic magmatism within the Baoshan Block has been considered weakly active due mainly to very limited exposures during the Hima... The Baoshan Block is tectonically located in the middle segment of the Sibumasu plate. Granitic magmatism within the Baoshan Block has been considered weakly active due mainly to very limited exposures during the Himalaya orogenic episode. The geochronological study on the buried Shuangmaidi granite has confirmed the existence of the Cenozoic granitoids in the Baoshan Block. The present study indicates that: (1) It is medium- to coarse-grained two mica phyric granite, characterized by high SiO2 (73.55%-77.16%) and low CaO (0.34%-1.38%) contents, with a total alkalis (K2O+Na2O) of 5.22%-8.03%, K2O/Na2O ratios of 0.24-1.79, and total rare earth elements (ZREE) of the granite between 85 and 125 ppb. All samples are enriched in light REE and exhibit medium negative Eu anomalies; and they show pronounced negative anomalies in Ba, Sr, Ti, and Nb but significant positive anomalies in K, Rb, U, Th, and Pb on mantle-normalized trace element patterns, indicating typi-cally peraluminous to strongly peraluminous S-type granite. (2) The zircon SHRIMP U-Pb ages of the granite are 36.27±0.48 Ma for the samples from ZK7-1 and 35.78±0.49 Ma for those from ZK0-1, respectively. The similar zircon ages from these two drill cores may suggest that the granite samples come from the same buried pluton. (3) 206pb/204pb values of the granite vary from 20.115 to 25.359, 207pb/204pb from 15.776 to 16.160, and 208pb/204pb from 39.236 to 41.285, showing the characteristics of radio- active lead anomaly of the upper crust. The (87Sr/86Sr)i values calculated on the average age of the two-mica orthoclase granite (36 Ma) range from 0.72524 to 0.77503 and eNd(t) values vary from -10.9 to -11.7. These data, along with the depleted-mantle Nd modal ages of 1.73-1.80 Ga, imply that the granites might have formed from partial melting of the Precambrian crystal basements. (4) On the Hf-Rb-Ta diagram, almost all the samples fall within the field of post-collision tectonic setting. The CaO/Na2O and A1203/TiO2 ratios suggest that the granitic magma may have formed from partial melting of clay-rich crustal materials with a pos- sible melting temperature of about 900℃ and a possible crystallization temperature of 775-795~C. (5) During the post-collision of the Himalaya orogen, with the southeastward extrusion of the Indochina continent resulting from the continuous northward indentation of the India continent into the Asia, the Gaoligong Fault, as the western boundary of the Indochina continent, moved in the dextral strike-slip on a large scale to trigger partial melting of the thickened crust, and the peraluminous granitic magma from which the Shuangmaidi two-mica orthoclase granite derived was formed. 展开更多
关键词 Upper Eocene peraluminous granite elements and Sr-Nd-Pb isotopic geochemistry Himalayan post-collision orogenic setting Baoshan Block southwestern China
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