新疆希勒库都克铜钼矿区岩浆混合作用: 来自锆石U-Pb年代学的证据   总被引：7，自引：6，他引：1  

龙灵利  王玉往  王京彬  王莉娟  李秋立  王书来  蒲克信  张会琼  廖震 《岩石学报》2010,26(2):449-456

新疆北部富蕴县内希勒库都克铜钼矿区的花岗闪长岩及其包体岩相学、矿物化学和岩石地球化学特征及野外地质特征显示其为岩浆混合作用的结果。本文获得花岗闪长岩及其中暗色微粒包体玄武安山玢岩、细粒辉长闪长岩锆石U-Pb年龄为326.8±2.1Ma、327.6±2.4Ma、329.3±2.3Ma,年龄值基本一致,这一结果从年代学角度为花岗闪长岩及其中暗色微粒包体的岩浆混合作用成因提供证据。偏酸性的花岗闪长质与偏基性玄武安山质岩浆混合作用形成了331.9±2.1Ma的安山玢岩脉。  相似文献   

A computationally efficient Doppler compensation system forunderwater acoustic communications     

Sharif  B.S. Neasham  J. Hinton  O.R. Adams  A.E. 《Oceanic Engineering, IEEE Journal of》2000,25(1):52-61

A Doppler compensation system is presented which is suitable for high-data-rate acoustic communication between rapidly moving platforms such as autonomous underwater vehicles. The proposed approach provides a generic preprocessor to conventional adaptive receiver structures with only a marginal increase in computational load and hardware cost. The preprocessor employs a novel Doppler estimation technique and efficient sample rate conversion to remove Doppler shift induced by platform velocity and acceleration. Performance predicted by simulation is compared to that of sea trials of a prototype communication system in the North Sea. Successful communication is demonstrated at 16 kbit/s with a transmitting platform moving at up to ±2.6 m/s  相似文献   

Performances of multi-element multi-user detection strategies in ashallow-water acoustic network (SWAN)     

Hong Kwang Yeo Sharif  B.S. Adams  A.E. Hinton  O.R. 《Oceanic Engineering, IEEE Journal of》2001,26(4):604-611

A multi-element receiver strategy is proposed in this paper for a multi-user shallow-water acoustic network (SWAN). The base station receiver, equipped with prior knowledge of the synchronization and training sequences of all intended users, has the task of demodulating the received signals of each user independent of the presence of other users. The adopted receiver strategy enables robust communications through the challenging underwater environment which is limited by both environmental and system factors. The channel is characterized by inter-symbol interference due to multipath propagation and multiple access interference. In this paper, we propose a number of multi-user detection receiver structures employing adaptive decision feedback equalization and spatial diversity to mitigate the effect of these two types of interference. Computer simulations and experimental sea trials conducted in the North Sea in 1999 were used to test the receiver strategies' performance for a two user near far scenario. Amongst a number of strategies tested, the structure based on recursive successive interference cancellation demonstrated improved performance overall  相似文献   

On the origin of red giant depletion through low-velocity collisions     

Tim Adams  Melvyn B. Davies  Alison Sills 《Monthly notices of the Royal Astronomical Society》2004,348(2):469-481

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The Southwest Indian Ridge: Remelting the Gondwanan Mantle     

JB Dick HENRY  Hole WOODS 《《地质学报》英文版》2015,89(Z2):27-27

<正>The Southwest Indian Ridge is an ultraslow spreading ridge(~14-mm/yr)that formed~150 Ma with the breakup of Gondwana.It extends 7700 km from the Bouvet to the Rodriguez Triple Junction,crossing over the flank of the large southern Geoid high centered over Marion and Crozet islands and the Conrad Rise.There is a  相似文献   

EVALUATION OF TWO FRACTAL METHODS FOR MAGNETOGRAM IMAGE ANALYSIS     

Stark  B.  Adams  M.  Hathaway  D. H.  Hagyard  M. J. 《Solar physics》1997,174(1-2):297-309

Fractal and multifractal techniques have been applied to various types of solar data to study the fractal properties of sunspots as well as the distribution of photospheric magnetic fields and the role of random motions on the solar surface in this distribution. Other research includes the investigation of changes in the fractal dimension as an indicator for solar flares. Here we evaluate the efficacy of two methods for determining the fractal dimension of an image data set: the Differential Box Counting scheme and a new method, the Jaenisch scheme. To determine the sensitivity of the techniques to changes in image complexity, various types of constructed images are analyzed. In addition, we apply this method to solar magnetogram data from Marshall Space Flight Center's vector magnetograph.  相似文献   

Ion-ion mutual neutralization and ion-neutral switching reactions of some stratospheric ions     

D. Smith  N.G. Adams  E. Alge 《Planetary and Space Science》1981,29(4):449-454

Following the recent mass spectrometric observations of the ambient stratospheric positive and negative ions we have carried out co-ordinated laboratory experiments using a selected ion flow tube apparatus and a flowing afterglow apparatus for the following purposes: (i) to consider whether CH₃CN is a viable candidate molecule for the species X in the observed stratospheric ion series H⁺ (H₂O_n (X)_m and (ii) to determine the binary mutual neutralization rate coefficients α_i for the reactions ofH⁺ (H₂O₄ and H⁺(H₂O)(CH₃CN)₃ with several of the negative ion species observed in the stratosphere. We conclude from (i) that CH₃CN is indeed a viable candidate for X and from (ii) that the α_i for stratospheric ions are within the limited range (5–6) × 10^?8 cm³ s^?1.  相似文献   

Spectral reflectance of highland rock types at Apollo 17: Evidence from Boulder 1, Station 2     

John B. Adams  Michael P. Charette 《Earth, Moon, and Planets》1975,14(3-4):483-489

Many of the non-mare rock types at Apollo 17 can be identified uniquely by their spectral reflectance properties. Mineralogical and textural information is present in the spectral curves of samples from Boulder 1, Station 2. It should be possible to determine the regional extent of rocks similar to the boulder using reflectance spectra from a spacecraft in lunar orbit.  相似文献   

Rock physics analysis for time-lapse seismic at Schiehallion Field, North Sea   总被引：1，自引：0，他引：1  

Mark Meadows  Don Adams  Rich Wright †  Ali Tura  Steve Cole  David Lumley 《Geophysical Prospecting》2005,53(2):205-213

Rock physics analysis plays a vital role in time‐lapse seismic interpretation because it provides the link between changes in rock and fluid properties and the resulting seismic data response. In this case study of the Schiehallion Field, we discuss a number of issues that commonly arise in rock physics analyses for time‐lapse studies. We show that:

• 1 Logarithmic fits of dry bulk (K_dry) and shear (G_dry) moduli vs. effective pressure (P_eff) are superior to polynomial fits.
• 2 2D surface fits of K_dry and G_dry over porosity (φ) and effective pressure using all the core data simultaneously are more useful and accurate than separate 1D fits over φ and P_eff for each individual core.
• 3 One average set (facies) of K_dry(φ, P_eff) and G_dry(φ, P_eff) can be chosen to represent adequately the entire Schiehallion reservoir.
• 4 Saturated velocities and densities modelled by fluid substitution of K_dry(φ, P_eff), G_dry(φ, P_eff) and the dry bulk density ρ_dry(φ) compare favourably with well‐log velocities and densities.
• 5 P‐ and S‐wave impedance values resulting from fluid substitution of K_dry(φ, P_eff), G_dry(φ, P_eff) and ρ_dry(φ) show that the largest impedance changes occur for high porosities and low effective pressures.
• 6 Uncertainties in K_dry(φ, P_eff) and G_dry(φ, P_eff) derived for individual cores can be used to generate error surfaces for these moduli that represent bounds for quantifying uncertainties in seismic modelling or pressure–saturation inversion.

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Assessing cause and effect of multiple stressors on marine systems     

Adams SM 《Marine pollution bulletin》2005,51(8-12):649-657

An operational framework is developed to serve as a guideline for investigating causal relationships between environmental stressors and effects on marine biota. Because of the complexity and variability of many marine systems, multiple lines of evidence are needed to understand relationships between stressors and effects on marine resources. Within this framework, a weight of evidence approach based on multiple lines of evidence are developed and applied in a sequential manner by (1) characterizing the study system which involves determining if target biota are impaired, assessment of food and habitat availability, and measuring contaminant levels in the environment, (2) assessing direct effects of contaminant exposure on target biota using biomarkers and assessing indirect effects of exposure using suites of bioindicators, and (3) applying standard causal criteria based on epidemiological principles and diagnostic health profiling techniques to assess potential causes. Use of multiple lines of evidence should also reduce the risk of false positives (Type I error or falsely concluding that there is a causal relationship when there is none) and false negatives (Type II error or falsely concluding there is not a causal relationship when there actually is). Understanding causal relationships and the mechanistic processes between environmental stressors and effects on biota is important in the effective management and restoration of impaired marine ecosystems.  相似文献