长江河口径流与盐度的谱分析   总被引：10，自引：1，他引：9  

沈焕庭  王晓春  杨清书 《海洋学报》2000,22(4):17-23

根据大通水文站的流量和引水船站的盐度系列资料,应用谱分析方法研究长江口径流、盐度的变化规律及两者的相互关系.分析表明,长江口径流存在4～8a,2～3a,1.5a,1a,30～60d及20d的及化周期;盐度存在5～10a,2～3a,1.5a,1a,0.5a,40～50d,26～30d,14～15d7～8d及3.5d的变化周期.径流和盐度的谱结构在各水文年基本一致,均以1a周期变化占优势,但盐度谱结构在高频部分较径流的谱结构具有更大的振荡.盐度与流量的5～10a,2～3a,1.5a,1a的周期振动上存在高相关.径流对盐度变化的影响主要体现在低频部分.在低频变化中表现为盐度变化滞后于径流变化,在高频带呈同步变化.  相似文献   

太阳活动区磁重联过程中电场加速高能电子分布的演化特征     

吴桂平  许敖敖  唐玉华 《天文学报》2000,41(4):393-399

基于活动区暗条快速上升后其下方电流片重联过程中产生强电场加速电子这一物理过程,解包括库仑碰撞和离子声湍动散射的Fokker-Planck方程,获得电子分布函数的演化特征．计算结果表明(1)当电场强度为1-10V·cm-1时,在10-5-10-6s可将电子加速到(0．1-1)Mev量级;(2)被加速电子近似呈幂律谱分布,其谱指数与耀斑脉冲相微波和硬X射线推断的电子谱指数基本吻合．  相似文献   

The hyperluminous infrared quasar 3C 318 and its implications for interpreting submm detections of high-redshift radio galaxies     

Chris J. Willott  Steve Rawlings  Matt J. Jarvis 《Monthly notices of the Royal Astronomical Society》2000,313(2):237-246

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Extended line emission around seven radio-loud quasars at redshift z ∼ 2     

R. J. Wilman  R. M. Johnstone  C. S. Crawford 《Monthly notices of the Royal Astronomical Society》2000,317(1):9-22

We present near-infrared spectra of seven radio-loud quasars with a median redshift of 2.1, five of which were previously known to have Ly α nebulae. Extended [O  iii ] λ 5007 and H α emission are evident around six objects, at the level of a few times 10⁻¹⁶ erg cm⁻² arcsec⁻² s⁻¹ within ≃2 arcsec of the nucleus (≡16 kpc in the adopted cosmology). Nuclear [O  ii ] λ 3727 is detected in three of the five quasars studied at this wavelength and clearly extended in one of them.
The extended [O  iii ] tends to be brighter on the side of the nucleus with the stronger, jet-like radio emission, indicating at least that the extranuclear gas is distributed anisotropically. It is also typically redshifted by several hundred km s⁻¹ from the nuclear [O  iii ], perhaps because of the latter being blueshifted from the host galaxy's systemic velocity. Alternatively, the velocity shifts could be due to infall (which is suggested by linewidths ∼1000 km s⁻¹ FWHM) in combination with a suitable dust geometry. Ly α /H α ratios well below the case B value suggest that some dust is present.
Photoionization modelling of the [O  iii ]/[O  ii ] ratios in the extended gas suggests that its pressure is around or less than a few times 10⁷ cm⁻³ K; any confining intracluster medium is thus likely to host a strong cooling flow. A comparison with lower redshift work suggests that there has been little evolution in the nuclear emission-line properties of radio-loud quasars between redshifts 1 and 2.  相似文献   

海洋微藻多糖微波提取法研究   总被引：1，自引：0，他引：1  

刘四光  李文权  邓永智 《海洋通报》2007,26(4):105-110

选取自养小球藻(Chlorella autotrophica)为实验材料,采用微波法提取多糖,以温度、时间、pH以及微波功率4个因子建立正交实验,考察单因素影响情况。实验结果表明,在温度70℃、时间30min、pH为7、功率为600W条件下粗多糖的产率最高,为291.13mg/g(粗多糖/干重),远高于传统热水浸提法所得粗多糖产率(78.52mg/g,粗多糖/干重),且所得粗多糖与热水浸提法获得的粗多糖具有相似的红外光谱。说明,在一定的实验条件下,与热水浸提法相比,微波提取法不仅不会破坏多糖的结构,还有耗时短、有较高的多糖产率的优势。  相似文献   

A method of determining dominant wave direction from multiparameter hydrological gauge measurements and its application     

WANG Sheng''an  LONG Xiaomin  ZHANG Keben  CHEN Junchang  ZHANG Wenjing  CAI Shuqun 《海洋学报(英文版)》2007,26(3):160-166

Multi-parameter hydrological gauge is an instrument developed by the South China Sea Institute of Oceanology,the Chinese Academy of Sciences to make simultaneous observation of current, wave, tide, water temperature and conductivity.By using the well-known "PUV method", the directional wave spectrum can be calculated and the dominant wave direction is then obtained.The comparison of the dominant wave directions derived from the measurements using both the multi-parameter hydrological gauge and the MARK Ⅱ "Wave-Rider" directional buoy shows that the dominant wave directions derived from the two kinds of measurements are in good agreement.  相似文献   

基于迭代重加权最小二乘法的雨滴谱函数拟合研究     

张宏群  陈思  周望  张晓宇  刘开辉 《气象科学》2022,42(2):235-243

传统的雨滴谱函数的拟合方法在不同的降水类型和不同分布函数下,可能存在拟合出来的雨滴谱函数与实际数据差异过大的情况,基于此问题,本文提出一种基于迭代重加权最小二乘法(Iterative Reweighed Least Square, IRLS)的雨滴谱函数拟合方法。利用Parsivel激光雨滴谱仪2019年7—10月在海南安定获得的225组层状云降水样本和110组对流云降水样本数据进行实验,通过不断更新权值,迭代计算,从而求出待估计参数。模拟结果表明了该方法应用在不同降水类型和不同分布函数下,对比阶矩法和最小二乘法得到的拟合优度都是最接近1的。  相似文献   

基于普通克里金外推的迭代维纳滤波法向下延拓     

朱文武  彭军还  罗三明  陈敏  申成锋  李永昆 《大地测量与地球动力学》2020,40(7):704-707

在利用普通克里金方法外推的基础上，通过频域径向平均功率谱估算噪声方差，采用迭代维纳滤波法获取较为稳定的重力场向下延拓结果，并分别利用模拟算例和实际数据进行实验。对于模拟算例，外推后的均方根误差由6.72 μGal下降到1.89 μGal，相对误差由9.26%下降到4.44%。对于实际数据，外推后延拓结果不仅可避免边缘失真现象，而且能更好地反映浅源高频异常特征信息。  相似文献   

脉冲星磁偶极辐射模型的修正     

贺龙松  吴鑫基  乔国俊  张承民 《中国天文和天体物理学报》1995,(3)

本文讨论了脉冲星磁偶极辐射模型所取得的成就和存在的困难，针对不足之处对磁偶极模型进行修正。从统计上得到修正因子与周期变率的幂律关系。由修正后的磁场强度得出其衰减时标大于１０８年，这与有关的理论研究结果一致。修正后的磁偶极模型给出周期变率和周期的新关系为р∝Ｐ－３，这恰好和р－Ｐ图中加速线以上的资料的统计拟合方程一致。  相似文献   

An upper limit to coronal X-rays from single,magnetic white dwarfs     

Rob Cavallo  Keith A. Arnaud  Virginia Trimble 《Journal of Astrophysics and Astronomy》1993,14(3-4):141-143

Pointed ROSAT PSPC exposures of 9277 and 6992 sec, directed toward the nearby, single, cool, magnetic white dwarfs GR 290 and EG 250 yielded no counts significantly above the expected background rate. The corresponding flux limits (for an assumed source temperature of l keV) are 1.0 and 1.7 × 10⁻¹⁴erg cm⁻² s⁻¹, within the 0.1–2.5 keV bandpass of the instrument (99% confidence limits). This is more than an order of magnitude below the tentative detection level (for GR 290) and limits (for four other similar stars) obtained from archival Einstein data in 1991. The corresponding limits on coronal electron density are comparable with those implied if cyclotron emission is not responsible for any of the features observed in the optical spectra of magnetic white dwarfs. X-ray data currently provide no evidence for the existence of coronae around these stars. A final long observation (25,000 sec of GD 356) is scheduled for later this year on ROSAT, along with coordinated EUVE observations.  相似文献