使用改进型破裂时间法对南加州做中期地震预测     

Brehm  DJ 杨国栋 《世界地震译丛》1999,(6):16-35

根据由南加州地震目录回顾性地震建模及已发表的对新马德里震带的估算结果,改进型破裂时间法可以作为一种中期地震预测技术用来确定未来主震的地点并预测其大小和时间。提出假设并对先前主震的建模表明本方法预测的离震震级精度达到了约±０．５个震级单位。假设已有兆序列中最后的事件,则破裂时间误差约是±１．１年。当不知识序列中最后的事件时,预测震级保持桢,但随着时间的推移,往序列中追加事件时,预测时间将需要更新。本  相似文献   

Patterns of inorganic phosphate uptake in Cassiopea xamachana: a bioindicator species     

Todd BD  Thornhill DJ  Fitt WK 《Marine pollution bulletin》2006,52(5):515-521

Nutrient levels in the nearshore waters of the Florida Keys have increased over the past few decades concomitant with a decline in the health of Florida's reef system. Phosphorus is a particular concern in the Florida Keys as it may be the limiting nutrient in nearshore waters. We demonstrate that the upside-down jellyfish, Cassiopea xamachana, decreases its rate of phosphate uptake following exposure to elevated levels of dissolved inorganic phosphate. We also show that this subsequent suppression of uptake rates persists for some time following exposure to elevated phosphates. Using these attributes, we experimentally investigated the use of C. xamachana as a bioindicator for dissolved inorganic phosphates in seawater. Our results show that these animals reveal comparative differences in environmental phosphates despite traditional testing methods yielding no detectable phosphates. We propose that C. xamachana is a bioindicator useful for integrating relevant information about phosphate availability in low nutrient environments.  相似文献   

关于“洋脊俯冲作用运动学及其对地幔上涌作用性质指示意义”的讨论     

Thor.  DJ 张春福 《地质科学译丛》1995,12(3):21-23

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瑞士阿尔卑斯山金矿化的新类型：迪森蒂斯金矿化     

Knopf  DJ 《地质地球化学》1991,(2):7-11,38

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二维地震波折射层析成象     

Whit.  DJ 梁惠云 《世界地震译丛》1993,(6):41-52

给出了一种用地震折射波初至走时确定二维速度的迭代层析成象反演法。该反演法适用于源－接收器间距比常规剖面法密的折射剖面，它是以线性化问题的迭代解为依据，不仅能用于近水平界面的几何形态，而且也能用于连续速度变化的情况。每次迭代中用射击法进行两点间的射线追踪，来建立线性系统。速度场用速度梯度为常数的三角形单元定义，这样射线路径可解析计算。根据正问题的不同线性化公式对两种不同的反演方法作了研究。用线性化走时－速度雅可比行列式反演得出的结果比用更近似于一般级数展开法的慢度公式的结果好。分辨率的例子不仅揭示了源－接收器组合方式及速度结构对分辨率的影响，而且也揭示了射线的几何形态造成的水平向模糊不清和分辨率随深度降低。反演例子表明，使用较好的初始模型时，整体范数产生的解比用最小扰动法计算的解更接近真实模型。对不均匀射线覆盖产生的条纹作用及其排除作了实例说明。  相似文献   

韩国的地球物理工作     

Jin.  DJ  史晓兰 《国土资源信息化》1994,(1):16-18

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Optical properties of benthic photosynthetic communities: fiber-optic studies of cyanobacterial mats     

Jorgensen BB  Des Marais DJ 《Limnology and oceanography》1988,33(1):99-113

A fiber-optic microphobe was used to analyze the spectral light gradients in benthic cyanobacterial mats with 50-micrometer depth resolution and 10-nm spectral resolution. Microcoleus chthononplastes mats were collected from hypersaline, coastal ponds at Guerrero Negro, Baja California. Gradients of spectral radiance, L, were measured at different angles through the mats and the spherically integrated scalar irradiance, Eo, was calculated. Maximal spectral light attenuation was found at the absorption peaks for the dominant photosynthetic pigments: chlorophyll a at 430 and 670 nm, carotenoids at 450-500 nm, phycocyanin at 620 nm, and bacteriochlorophyll a at 800-900 nm. Scattered light had a marked spectral effect on the scalar irradiance which near the mat surface reached up to 190% of the incident irradiance. The spherically integrated irradiance thus differed strongly from the incident irradiance both in total intensity and in spectral composition. These basic optical properties are important for the understanding of photosynthesis and light harvesting in benthic and epiphytic communities.  相似文献   

沉积作用简单方程在层序地层学中的应用     

Cant.  DJ 何登发 《国外地质与勘测》1991,(2):6-13

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A reanalysis of the HCO+/HOC+ abundance ratio in dense interstellar clouds     

Jarrold MF  Bowers MT  DeFrees DJ  McLean AD  Herbst E 《The Astrophysical journal》1986,303(1):392-400

New theoretical and experimental results have prompted a reinvestigation of the HCO+/HOC+ abundance ratio in dense interstellar clouds. These results pertain principally but not exclusively to the reaction between HOC+ and H2, which was previously calculated by DeFrees, McLean, and Herbst to possess a large activation energy barrier. New calculations, reported here, indicate that this activation energy barrier is quite small and may well be zero. In addition, experimental results at higher energy and temperature indicate strongly that the reaction proceeds efficiently at interstellar temperatures. If HOC+ does indeed react efficiently with H2 in interstellar clouds, the calculated HCO+/HOC+ abundance ratio rises to substantially greater value under standard dense cloud conditions than in deduced via the tentative observation of HOC+ in Sgr B2.  相似文献   

Ab initio molecular orbital studies of low-energy, metastable isomers of the ubiquitous cyclopropenylidene     

DeFrees DJ  McLean AD 《The Astrophysical journal》1986,308(1):L31-L35

The discovery of cyclopropenylidene in space suggests that other C3H2 isomers may be present and a tentative detection of one such isomer, propargylene (HCCCH), has been reported. Ab initio molecular orbital theory has been used to characterize five low-lying, metastable isomers of cyclopropenylidene. Four are found to be stable minima and their vibrational frequencies are reported, although the stable form of triplet propargylene is not firmly established. Extended calculations including the electron correlation energy, show that the lowest in energy is singlet propadienylidene, followed by propargylene; the singlet and triplet of the latter are too close in energy to allow an assignment of the ground state; triplet propadienylidene is at a significantly higher energy. Rotational frequencies computed to an expected accuracy of +/- 1%-2% do not confirm the tentative detection of propargylene in space, although the discrepancy between theory and the observation is not so great as to unequivocally rule out this possibility.  相似文献