共查询到20条相似文献,搜索用时 79 毫秒
1.
2.
3.
4.
5.
《Journal of The Franklin Institute》1987,324(1):27-42
A new algorithm to reconstruct a one-dimensional sequence from its Fourier transform magnitude and 1-bit phase information is presented. Since the minimum-phase and maximum-phase sequences are uniquely specified by the magnitude alone, the algorithm reconstructs these sequences from magnitude only but it requires additional sign information in the case of mixed-phase signals. A minimum or maximum-phase sequence is recursively obtained using the cepstrum of the given magnitude function. In the case of mixed-phase sequences the sequence calculated from the magnitude is the minimum-phase equivalent of the original sequence. This together with the 1-bit phase information permits us to obtain by interpolation an approximation of the original phase and therefore reconstruct the sequence. To reduce the computational effort, we propose a test to distinguish between the minimum (maximum) and mixed-phase sequences using the sign information. With this additional information, the procedure becomes very efficient. We compare the reconstruction of signals using our algorithm with that obtained by well known iterative methods. 相似文献
6.
自由文本信息抽取技术 总被引:13,自引:0,他引:13
信息抽取是从自由文本语料库构建数据库,实现情报自动收集的有效途径之一。近十多年来,信息抽取技术逐步走向成熟,已成为与信息检索相平行的技术之一。对信息抽取技术进行系统的归类、总结,已显得较为迫切。在对当前多种主要的信息抽取技术进行分析、比较的基础上,结合信息抽取所面临的挑战,分析了信息抽取的三个趋势。 相似文献
7.
8.
对难选镍钼多金属矿进行了湿法工艺浸出试验研究。对纯碱用量、片碱用量、浸出液固比、浸出时间、浸出温度等条件进行了试验研究,确定了各个因素最佳条件:在碱性条件下、液固比为3∶1、温度90℃条件下浸出时间3h后,钼的浸出率达96%。 相似文献
9.
基于MODIS时序NDVI特征值提取多作物播种面积的方法 总被引:35,自引:0,他引:35
MODIS数据的1、2波段是具有250m空间分辨率的红和近红外波段,并具有较高的时间分辨率,可对农作物进行动态跟踪监测.随着农作物的生长,NDVI值逐渐增大,并在一定生育期达到最大值后开始下降.由于不同作物具有不同的生育期,NDVI峰值的大小、出现的时间各不相同.通过对北京市主要农作物的种植结构调查和3月中旬到11月上旬的不同作物的NDVI值采样分析,得出:①冬小麦NDVI值3月下旬相对较高,5月上旬最大;②春玉米的NDVI峰值出现于8月上旬;③夏玉米的NDVI峰值出现于8月中旬;④大豆的NDVI峰值也出现在8月中上旬,可通过物候历与春玉米区分开来(春玉米是单季作物,大豆是双季作物),通过峰值大小与夏玉米区分开来.结合北京市1:10万土地利用数据,通过NDVI值时序变化规律从MODIS数据中提取了冬小麦、春玉米、夏玉米、大豆等作物的种植面积,总体精度达到95%以上. 相似文献
10.
以大量实例分析,归纳了ILASⅡ系统中数据著录95字段的内涵以及音序拼号法著者号提取的具体方法。 相似文献
11.
12.
13.
14.
15.
16.
The paper examines the formation of clique-spanning ties in intra-corporate co-invention networks, by focusing on the impact of R&D unit spinouts. Using data on thirty-one spinouts in eight large U.S. information and communication technology corporations, we show that the reorganization of R&D units through corporate spinouts is associated with an increase in the extent to which inventors employed in the unit collaborate with inventors located in other cliques within the corporate co-invention network. Interestingly, the spinout effect spills over to all members of the clique of spun-out inventors, also including those who remain with the parent firm. The interpretation of these empirical findings, grounded on existing theories and on the views of inventors and executives involved in the reorganization events, suggests that corporate spinouts generate a shock in intra-corporate research collaboration dynamics, which loosens clique lock-in effects and contributes to reset cliques’ boundaries in the intra-corporate research network. 相似文献
17.
18.
以地形粗糙度为主要研究内容,给出飞行器目标地形灰度图像的预处理算法和地形粗糙度提取算法,并完成了计算单元地形特征提取。分析了基于噪声特性和退化函数算法算法的灰度图像滤波的基本原理;研究了基于合适尺寸计算单元灰度算法的目标地形粗糙度提取算法,并建立了相应的数学模型;通过应用某数字地形灰度图像进行仿真验算,证明了基于灰度图像的地形粗糙度信息提取方法的可行性;为精确识别地外行星目标地形信息并对地形进行风险评估提出了一种新的研究思路。 相似文献
19.