新型天气雷达发射脉冲包络检测集成系统设计与实现     

李力  陈宁  程昌玉  张福贵  甘少明 《气象科技》2017,45(6):1112-1115

实现一种新型天气雷达发射脉冲包络检测集成技术,高度集成数控衰减器、包络检波器、A/D转换器和FPGA(Field Programmable Gate Array)处理器;能快速准确的对发射机脉冲特性进行检测,无需其他仪器和工具辅助,全自动测试,自动生成测试报告并根据测试结果给出检修建议,能够有效解决台站天气雷达对发射脉冲包络传统测试和维护的单一测试仪器功能,有效降低人为测试误差,减少天气雷达故障诊断和日常维护带来的制约和影响,促进天气雷达测试、维护维修保障的标准化和自动化。  相似文献   

The hydrodynamic response of the York River estuary to Tropical Cyclone Isabel, 2003   总被引：3，自引：0，他引：3  

Wenping Gong  Jian Shen  William G. Reay 《Estuarine, Coastal and Shelf Science》2007,73(3-4):695-710

Hurricane Isabel made landfall along the North Carolina coast on September 18, 2003 (UTC 17:00) and the storm surge exceeded 2.0 m in many areas of the Chesapeake Bay and in the York River estuary. River flooding occurred subsequently, and the peak river discharge reached 317 and 104 m³ s⁻¹ in the Pamunkey and Mattaponi rivers, respectively. The York River estuary experienced both storm surge and river flooding during the event and the estuary dynamics changed dramatically. This study investigates the hydrodynamics of the York River estuary in response to the storm surge and high river inflows. A three-dimensional model was used to investigate the changes of estuarine stratification, longitudinal circulation, salt flux mechanisms, and the recovery time required for the estuary to return to its naturally evolved condition without the storm. Results show that the salt flux was mainly caused by advection, which was induced by the barotropic gradient during the storm event. The net salt flux increased by a factor of 30 during the rise of the storm surge. However, the large amount of salt transported into the estuary was quickly transported out of the estuary as the barotropic gradient reversed during the descent of the storm surge. Subsequent high freshwater inflow influenced the estuarine circulation substantially. The estuary changed from a partially mixed estuary to a very stratified estuary for a prolonged period. The model results show that it will take about 4 months for the estuary to recover to its naturally evolved salinity distribution after the impacts of the storm surge and freshwater pulse.  相似文献   

脉冲激励式多路传感器接口电路     

廉双喜  邹强 《海洋技术学报》2001,20(4):60-65,68

本文介绍的脉冲激励式多路传感器接口电路，在一个等幅脉冲源对多路传感器激励的同时，用一个由串行DAC和比较器组成的逐位逼近ADC。受控于87C51单片机，完成多路信道的数字化，作者已完成的12位ADC，由一个5V脉冲源激励C、T、D、pH、DO、Ref等传感器，每30s一次8路扫描。该电路简单、经济，特别适合于需要交流激励的水质传感器及水质检测。  相似文献   

水声传播中线性调频脉冲信号的检测方法研究     

刘贞文  杨燕明 《台湾海峡》2007,26(1):141-148

本文分析了线性调频脉冲信号的特点并用脉冲压缩方法来检测线性调频信号波形，特别是用脉冲压缩方法来检测会聚区信号，更能体现脉冲压缩具有降低噪声均值，获得较高信噪比增益，提高距离分辨率的优点．  相似文献   

Time-based signal characteristics as predictors of fish size and species for a side-looking hydroacoustic application in a river   总被引：1，自引：1，他引：1  

Burwen  Debby L; Fleischman  Steven J; Miller  James D; Jensen  Mark E 《ICES Journal of Marine Science》2003,60(3):662-668

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点火脉冲对GRACE加速度计校准的影响     

吴林冲  衷路萍  刘冰石 《大地测量与地球动力学》2018,38(4):399-401

GRACE卫星搭载的高精度SuperSTAR加速度计观测数据包含点火脉冲信号，本文分析点火脉冲数据特点，讨论点火脉冲对加速度计校准结果(尺度参数和偏差参数)的影响。2008-04一个月的加速度计实测数据分析表明，点火脉冲对尺度参数、比例参数的影响最大分别为0.02、10-7m·s-2，对加速度校准结果的影响在Y、Z方向上高达10-10m·s-2。  相似文献   

Allometric relations between fluvial impulse and morphometric parameters of floodplain lakes          下载免费PDF全文

Beata Ferencz  Jarosław Dawidek 《水文研究》2016,30(4):534-542

The general role of river water input in shaping the basic morphometric parameters of floodplain lakes has been previously investigated. However, the process has not been quantitatively described in detail. This study is the first attempt in the literature to determine the allometric relation between fluvial impulse, expressed as Fluvial Connectivity Quotient, and morphometric parameters of six floodplain lakes of Bug River valley in the period 1952–2014. This relationship is given by Y = aX^b, from which the value of b exponent was analysed to determine the strength of the allometric relation. Extreme values of allometric compounds during the time period under study ranged from 5.99 to ?4.91. Volume was the morphometric parameter showing the highest variability in all the lakes. General similarity in allometric relations was observed in the lakes under study. During analysis, no long‐term trends were observed in the relationship between the Fluvial Connectivity Quotient and morphometric parameters. The results obtained show that fluvial impulse was the factor determining the variability of morphometric parameters of the lakes. Direct catchments topography of lake has periodically (during limnophase periods) played a significant role in shaping the morphometry of floodplain lakes. The most stable allometric relations occurred in a confluent lake, with a low limnological effective rise value and consequently, relatively long potamophase periods.Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Characterization of water quality variation in the Mekong River at Vientiane by frequent observations     

Toshiaki Iida  Somphone Inkhamseng  Koshi Yoshida  Hajime Tanji 《水文研究》2011,25(23):3590-3601

To better understand the variation of water quality in the Mekong River, sampling and measurement were scheduled twice a week for about 3 years at Vientiane, followed by basic statistical analysis of the observed data. The frequent measurement revealed detailed characteristics of the water quality variation, which had not been detected by monthly observation in the previous studies. The variation in total ionic content was considered to be governed by dilution of the amount of water. Increases in turbidity could be attributed to physical effects including surface soil erosion and bed material resuspension at the time of discharge increase. Nitrogen concentrations were stably low during the low flow period and abruptly increased in May. After the annual maximum in late May, the nitrate concentration steadily decreased regardless of the remarkable rise in the discharge from mid‐July, whereas the ammonium concentration remained at a similar level until October. It was considered that the first small discernable runoff after the long dry season flushed the accumulated nitrogen in the surface soil and mobilized the nitrogen in the riverbed. The variation in phosphorus concentrations was different from that in nitrogen concentrations. During the high flow period, continual dilutions at discharge peaks and occasional large additions of phosphorus by surface runoff were suggested. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Response of sediment dynamics in the York River Estuary,USA to tropical cyclone Isabel of 2003     

Wenping Gong  Jian Shen 《Estuarine, Coastal and Shelf Science》2009

Tropical Cyclone Isabel of 2003 generated large storm surge, strong waves, and subsequent river flooding in the York River Estuary, USA during its passage across the Chesapeake Bay region. A 3D model was used to investigate the changes of sediment concentration, sediment flux, and the recovery time of the York River Estuary to its naturally evolved condition without the storm. The results showed that two sediment concentration peaks appeared during the storm event. The first one was induced by the large upstream flow and waves during the storm surge rising period, and the later one was caused by the strong downstream flow during the descent of the storm surge. The advection, which was induced by the barotropic gradient, dominated the sediment flux during the storm event. The sediment fluxes increased by a factor of 100 during the rise and descent of the storm surge. A large amount of sediment that was transported into the estuary and eroded from the seabed during the rising of the storm surge was quickly transported out of the estuary during the descent of the storm surge. Waves played a key role in stirring the seabed and increasing the sediment concentration during the storm. Subsequent high freshwater inflow changed the sediment loading and hydrodynamics in the estuary, and thus, influenced the estuarine turbidity maximum (ETM) dynamics profoundly. The ETM moved downstream with the river flooding initially and returned upstream with the waning of river flooding and the re-establishment of gravitational circulation. The effect of river flooding on sediment concentration varied spatially and depended on the changes of ETM locations and vertical mixing. The model results suggest that a large amount of sediment was transported out of the estuary during the storm event and the subsequent river flooding had a larger impact on recovery time of the estuary.  相似文献   

Evaluating impacts of pulse fishing on the effectiveness of seasonal closure     

邢磊  陈勇  张崇良  李拜  Yunne-Jai Shin  任一平 《海洋学报(英文版)》2020,39(4):89-99

Seasonal fishing closures are often used in fisheries management to conserve overfished stocks.As one of the unintended consequences,fishermen often contend for maximizing catches immediately after reopening fisheries.The resultant large catch landings in a short time period(i.e.,pulse fishing)may undermine the benefit of closure.We implemented an end-to-end model OSMOSE-JZB(Object-oriented Simulator of Marine ec OSystem Exploitation OSMOSE)modelling ecosystem in the Jiaozhou Bay located in China to evaluate the impact of pulse fishing on the effectiveness of seasonal closure at levels of fish community,population,and individual.Our study demonstrated that the three-month closure was successful in conserving fish stocks.There were small variations on ecological indicators(i.e.,total biomass of the community,mean trophic level of the community,mean trophic level of the catch,and Shannon-Wiener biodiversity index)when pulse fishing occurred.Pulse fishing seemed not to result in a great shift in community structure.Compared to other species,the biomass of two large predatory fishes were more susceptible to pulse fishing.Pulse fishing could change the pressure of predators to fish stocks via food webs,especially for young individuals.Our simulations indicate that we can improve the effectiveness of seasonal closure by managing pulse fishing.Although the results derived in this study may be specific to the target ecosystem,the general approach is applicable to other ecosystems when evaluating fishing impacts.  相似文献