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191.
The detection of tonals embedded in noise is an important sonar function and the traditional power spectrum analysis method has been widely used for this purpose. Wagstaff et al. (1997) proposed the WISPR (Wagstaff's Integration Silencing PRocessor) family processors, which perform a nonlinear integration or combination of the power spectrum observations. In this paper, we analyze the statistical property of the power spectrum observations and develop novel tonal detectors by optimally integrating the spectrum observations. The optimal detectors are derived by using the method of maximum likelihood hypothesis test. The results from simulations and real sea trial data have shown that the proposed detectors are promising in detecting tonals 相似文献
192.
观察了双棘黄姑鱼卵巢发育的周年变化,结果表明,双棘黄姑鱼雌鱼性腺成熟系数(GSI)一年有两个峰值,分别出现在5月份(9.38%±0.32%)和10月份(7.56%±0.43%);HSI与GSI密切相关[R=0.76];卵巢发育水温在19~29℃范围,繁殖水温为24~28℃,在广东省饶平海区,双棘黄姑鱼繁殖时间在每年的5月和10月,属于春、秋二季产卵类型的鱼类。 相似文献
193.
Analyzing daily values of the total solar irradiance (TSI), the coronal index of solar activity (CI), and the Mg II 280-nm
core-to-wing ratio (Mg II index), we have found that the temporal variations of these indices are very similar to each other
during the period from 1978 to 2005. The correlation between CI and TSI, with the PSI correction lying within the interval
under study, has been found to be 0.699, which is very close to the value of 0.703 of the correlation between Mg II and TSI
for 27-day averages (the CI – Mg correlation is 0.824). The regression equation between CI and TSI is almost linear, except
for TSI depletions when a large number of sunspots are present on the visible disk. By employing CI, an extrapolation of TSI
back to 1947 is presented. 相似文献
194.
Using the Greenwich Photoheliographic Results for the years 1874–1976 the daily rotational velocities for 955 recurrent and
13169 non-recurrent sunspot groups from the first day of their appearance and during their evolution have been determined.
The rotational velocities were divided in six latitude strips with a width of five degrees and grouped according to the age
of the groups. It was established that the rotational velocities of recurrent and non-recurrent sunspot groups decrease with
time in all studied latitude strips. At their birth the recurrent spot groups rotate faster by about 0.15° day−1 than the non-recurrent ones and settle, within the errors of measurements, to an about 0.5° day−1 slower velocity value during the second disc passage. A comparison of our results with helioseismology measurements indicates
that in the frame of the anchoring hypothesis, the recurrent sunspot groups at their birth could be coupled to the fast rotating
layer at about r=0.93 R
⊙. 相似文献
195.
This study focuses mainly on observing urban development in Taiwan's Wu‐Tu watershed from the perspective of urban hydrological theory. An approach is proposed for developing a method for incorporating available meteorological data to define the degree of change in a runoff hydrograph for urbanizing basins. The mean rainfall was estimated using the Kriging method. For calibration, two methods of calculating the effective rainfall (the Φ‐index method and the non‐linear‐programming (NLP) method) were used as model inputs, and the optimal global parameters of the linear reservoir model were then obtained from the shuffled complex evolution (SCE) algorithm. Twenty‐six (1966–1991) and eight (1994–1997) rainfall–runoff events were used for calibration and verification, respectively. The NLP method yielded better results than the Φ‐index method, especially for multipeak rainfall–runoff events. The regression equation determined the relationship between the parameters of the model and impervious areas. A comparison based on the results of the instantaneous unit hydrograph of the study area revealed that three decades of urbanization had increased the peak flow by 27%, and the time to peak was decreased by 4 h. The study simply describes the results of the impact of imperviousness on hydrological modelling. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
196.
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198.
Yuyuan Li Ru Gao Rui Yang Hongan Wei Yong Li Heai Xiao Jinshui Wu 《洁净——土壤、空气、水》2013,41(11):1100-1107
The impacts of soil P leaching on water eutrophication have widely been concerned. However, there is no dependable method to quantitatively estimate the P leaching risk of soils. In this study, a simple soil column method was developed using two calcareous Fluvisols, silt loam and loam. The soil column was 20 cm in length and 5 cm in diameter, and distilled water was continuously supplied from the top. The volume and dissolved reactive P (DRP) concentrations of leachate were measured. Results showed that DRP concentrations in leachate increased slowly for the low soil Olsen‐P levels but rapidly for the high Olsen‐P levels. According to these two‐phase changes in the DRP versus soil Olsen‐P contents, the thresholds of P leaching risk were estimated to be 41.1 and 62.3 mg P kg?1 (Olsen‐P) for silt loam and loam, respectively. The P leaching intensity of soils increased by 3‐ to 540‐fold if the soil Olsen‐P contents accumulated from 6.6 to 155.5 mg P kg?1. The outcomes derived from this study regarding the determination of P leaching threshold and intensity by the soil column method also need a further verification on more soils with a wide range of physical and chemical properties. 相似文献
199.
200.
为探究多环芳烃(Polycyclic aromatic hydrocarbons,PAHs)污染对海洋桡足类的毒性效应,本研究以日本虎斑猛水蚤(Tigriopus japonicus)为受试生物,选取菲(Phenanthrene,Phe)作为PAHs的代表开展暴露试验.急性毒性试验测得Phe对日本虎斑猛水蚤的96 h半... 相似文献