基于经验模态分解的曲波阈值去噪方法     

董烈乾  李振春  刘磊  李志娜  桑运云 《吉林大学学报(地球科学版)》2012,42(3):838-844

针对曲波阈值去噪方法阈值选取单一造成的有效信号损失或随机噪声压制不完全的问题,笔者提出了一种基于经验模态分解的曲波阈值去噪方法。该方法首先对带噪信号进行经验模态分解得到一系列固有模态函数,根据每个固有模态函数所含噪声强弱的不同,选取不同的阈值分别对分解得到的含噪固有模态函数进行曲波阈值降噪处理;最后将去噪后的固有模态函数与不含噪声的固有模态函数进行信号重构得到最终压噪的结果。由于引入经验模态分解,对分解得到的不同含噪程度的固有模态函数,选取不同的阈值进行处理,这样能够有效减小直接曲波阈值方法阈值选取单一产生的问题。模型和实际数据试算表明,该方法在提高数据信噪比的同时,能够有效地保留有效信号,是一种相对保幅的去噪方法。  相似文献   

Pattern and origin of spherulites in a rhyolite dike swarm,northeastern Cheongsong, Korea     

Sang Koo Hwang Chang Oh Choo 《东北亚地学研究》2006,9(1):60-79

IntroductionThe northeastern Cheongsong area is underlainby a sequence of sedi mentary rocks together within-trusive and extrusive volcanic rocks all of late Creta-ceous age(Lee&Hong,1973;Ki m&Park,1970;Hwang,1998).Theintrusions,comprising astock,a plug and numerous dikes,are well exposedat the current surface due tothe enormous erosion ofany sedi mentary or volcanic covered rocks.Thedikes forma dike swarmand some are intruded intothe plug.The dikes swarm may represent the subsurfaceexpress…  相似文献   

Winter AO/NAO modifies summer ocean heat content and monsoonal circulation over the western Indian Ocean          下载免费PDF全文

Dao-Yi Gong  Dong Guo  Sang Li  Seong-Joong Kim 《Acta Meteorologica Sinica》2017,31(1):94-106

This paper analyzes the possible influence of boreal winter Arctic Oscillation/North Atlantic Oscillation (AO/ NAO) on the Indian Ocean upper ocean heat content in summer as well as the summer monsoonal circulation. The strong interannual co-variation between winter 1000-hPa geopotential height in the Northern Hemisphere and summer ocean heat content in the uppermost 120 m over the tropical Indian Ocean was investigated by a singular decomposition analysis for the period 1979–2014. The second paired-modes explain 23.8% of the squared covariance, and reveal an AO/NAO pattern over the North Atlantic and a warming upper ocean in the western tropical Indian Ocean. The positive upper ocean heat content enhances evaporation and convection, and results in an anomalous meridional circulation with ascending motion over 5°S–5°N and descending over 15°–25°N. Correspondingly, in the lower troposphere, significantly anomalous northerly winds appear over the western Indian Ocean north of the equator, implying a weaker summer monsoon circulation. The off-equator oceanic Rossby wave plays a key role in linking the AO/NAO and the summer heat content anomalies. In boreal winter, a positive AO/NAO triggers a down-welling Rossby wave in the central tropical Indian Ocean through the atmospheric teleconnection. As the Rossby wave arrives in the western Indian Ocean in summer, it results in anomalous upper ocean heating near the equator mainly through the meridional advection. The AO/NAO-forced Rossby wave and the resultant upper ocean warming are well reproduced by an ocean circulation model. The winter AO/NAO could be a potential season-lead driver of the summer atmospheric circulation over the northwestern Indian Ocean.  相似文献   

Spectral dependence on the correction factor of erythemal UV for cloud,aerosol, total ozone,and surface properties: A modeling study     

Sang Seo Park  Yeonjin Jung  Yun Gon Lee 《大气科学进展》2016,33(7):865-874

Radiative transfer model simulations were used to investigate the erythemal ultraviolet(EUV) correction factors by separating the UV-A and UV-B spectral ranges. The correction factor was defined as the ratio of EUV caused by changing the amounts and characteristics of the extinction and scattering materials. The EUV correction factors(CFEUV) for UV-A[CFEUV(A)] and UV-B [CFEUV(B)] were affected by changes in the total ozone, optical depths of aerosol and cloud, and the solar zenith angle. The differences between CFEUV(A) and CFEUV(B) were also estimated as a function of solar zenith angle, the optical depths of aerosol and cloud, and total ozone. The differences between CFEUV(A) and CFEUV(B) ranged from-5.0% to 25.0% for aerosols, and from-9.5% to 2.0% for clouds in all simulations for different solar zenith angles and optical depths of aerosol and cloud. The rate of decline of CFEUV per unit optical depth between UV-A and UV-B differed by up to 20% for the same aerosol and cloud conditions. For total ozone, the variation in CFEUV(A) was negligible compared with that in CFEUV(B) because of the effective spectral range of the ozone absorption band. In addition, the sensitivity of the CFEUVs due to changes in surface conditions(i.e., surface albedo and surface altitude) was also estimated by using the model in this study. For changes in surface albedo, the sensitivity of the CFEUVs was 2.9%–4.1% per 0.1 albedo change,depending on the amount of aerosols or clouds. For changes in surface altitude, the sensitivity of CFEUV(B) was twice that of CFEUV(A), because the Rayleigh optical depth increased significantly at shorter wavelengths.  相似文献   

Geostatistical techniques to evaluate groundwater contamination and its sources in Miryang City,Korea     

Senapathi Venkatramanan  Sang Yong Chung  Tae Hyung Kim  Byung-Woo Kim  Sekar Selvam 《Environmental Earth Sciences》2016,75(11):994

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A preliminary study on the offshore stratigraphy in Hong Kong and its hydrogeological implications     

Hiu Tung Kwong  Jiu Jimmy Jiao  Lung Sang Chan 《Environmental Earth Sciences》2016,75(11):975

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Time series analyses of hydrological parameter variations and their correlations at a coastal area in Busan,South Korea     

Sang Yong Chung  Venkatramanan Senapathi  Selvam Sekar  Tae Hyung Kim 《Hydrogeology Journal》2018,26(6):1875-1885

Monitoring and time-series analysis of the hydrological parameters electrical conductivity (EC), water pressure, precipitation and tide were carried out, to understand the characteristics of the parameter variations and their correlations at a coastal area in Busan, South Korea. The monitoring data were collected at a sharp interface between freshwater and saline water at the depth of 25 m below ground. Two well-logging profiles showed that seawater intrusion has largely expanded (progressed inland), and has greatly affected the groundwater quality in a coastal aquifer of tuffaceous sedimentary rock over a 9-year period. According to the time series analyses, the periodograms of the hydrological parameters present very similar trends to the power spectral densities (PSD) of the hydrological parameters. Autocorrelation functions (ACF) and partial autocorrelation functions (PACF) of the hydrological parameters were produced to evaluate their self-correlations. The ACFs of all hydrologic parameters showed very good correlation over the entire time lag, but the PACF revealed that the correlations were good only at time lag 1. Crosscorrelation functions (CCF) were used to evaluate the correlations between the hydrological parameters and the characteristics of seawater intrusion in the coastal aquifer system. The CCFs showed that EC had a close relationship with water pressure and precipitation rather than tide. The CCFs of water pressure with tide and precipitation were in inverse proportion, and the CCF of water pressure with precipitation was larger than that with tide.  相似文献   

铀矿勘查中地表探矿工程成果信息化研究与实践——放射性测量数据自动化成图     

邱日平  沈川  滕润球  肖磉  严家斌 《铀矿地质》2021,(1):112-119

铀矿勘查中,实施地表探矿工程来揭示区内地质及矿化现象是一个行之有效且常用的方法,其矿化成果信息主要由放射性测量成果图件展现,目前主要靠手工素描完成,但存在费时且图件不美观等问题。因此,笔者提出了自动化成图的构想,开发了一款辅助软件来对放射性测量数据进行数据处理,将多参数坐标转换为标准坐标格式,支持Surfer软件数据网格化处理和Mapgis软件输出成果图件,实现自动化成图。经大量地表工程验证,证实辅助软件输出数据准确、可靠,通过Surfer、Mapgis软件实现了放射性测量数据自动化成图。此方法可取代传统手工素描绘图和Mapgis软件矢量化成图等耗时的步骤,将为放射性编录工作带来极大便利,进一步提升成果图件的标准化,提高物探编录的工作效率。  相似文献   

粉土与粉质黏土互层中静压桩桩土界面孔隙水压力     

桑松魁  王永洪  张明义  孔亮  吴文兵  陈志雄  李兆龙  张启军 《吉林大学学报(地球科学版)》2021,51(5):1551-1559

为研究层状黏性土在静压桩沉桩过程中桩土界面孔隙水压力的分布规律,依托山东东营某桩基工程开展了现场足尺静压桩试验,分析了桩土界面孔隙水压力的变化规律,探讨了桩土界面超孔隙水压力的分布特征,明确了桩土界面孔隙水压力和超孔隙水压力的消散特性,并结合水力压裂理论和孔穴扩张理论,揭示了沉桩过程中桩土界面沿桩长方向超孔隙水压力的分布形式。试验结果表明：孔隙水压力、超孔隙水压力与土层性质密切相关,二者均在粉土层中增长较慢,在粉质黏土层中增长较快;在同一深度处,两者均存在明显的消散现象,在粉土中的消散程度明显大于粉质黏土中;采用水力压裂理论结合孔穴扩张理论计算的超孔隙水压力沿桩长方向的变化规律与试验值相吻合;桩身贯入深度越大,超孔隙水压力理论计算值与现场实测值越接近。  相似文献   

Estimation of submarine groundwater discharge in the Il‐Gwang watershed using water budget analysis and 222Rn mass balance          下载免费PDF全文

Yong‐Seok Gwak  Sang‐Hyun Kim  Yong‐Woo Lee  Boo‐Keun Khim  Se‐Yeong Hamm  Sung‐Wok Kim 《水文研究》2014,28(11):3761-3775

Submarine groundwater discharges (SGD) were investigated in a marine watershed in south‐eastern Korea using water budget analysis and a ²²²Rn mass balance model. Multi‐layered TOPMODEL added hydrological assumption was used to estimate groundwater components in the water budget analysis. Field observations of soil moisture, rainfall, runoff and groundwater fluctuations were used for calibration and validation of the hydrologic model. Based on observed hydrological data and terrain analyses, parameters for the hydrologic model were delineated and used to describe several hydrologic responses in the watershed. SGD estimations by ²²²Rn mass balance method were also performed at Il‐Gwang bay in July, 2010, and May, June, July and Nov. 2011. The estimated groundwater through hydrologic modeling and water balance analysis was 1.3x10⁶ m³/year, which rapidly increased during typhoon season due to heavy rainfall and permeable geologic structure. The estimated groundwater was approximately 3.7–27.1% of SGD as evaluated by ²²²Rn mass balance method ranges 3.44 and 17.45 m³m^?2year^?1. Even though SGD is predominantly influenced by tide fluctuation, the head gradient (difference) from hydrologic processes associated with heavy rainfalls can also have extra significant influences. Comprehensive understanding of SGD evaluation can be improved through a simultaneous application of both these approaches. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献