Three-dimensional diffraction of elastic waves by a spherical cavity in an elastic half-space, I: Closed-form solutions     

Vincent W. Lee 《Soil Dynamics and Earthquake Engineering》1988,7(3)

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On the speciation of metals in the water column of a polluted estuary     

George W. Luther III  Zbigniew Wilk  Robert A. Ryans  A. Lee Meyerson 《Marine pollution bulletin》1986,17(12):535-542

The dissolved (<0.40 γm) fraction of water samples from Newark Bay, New Jersey was analysed for Zn, Cu and Pb content by differential pulse anodic stripping polarographic techniques. In the dissolved fraction, non-labile forms of Zn, Cu and Pb exist as shown by differential pulse anodic stripping voltammetry analysis on acidified samples and acidified-UV irradiated samples. The particulate fraction (>;0.40 μm) contains metals in the form of sulphides (Fe, Zn, Cu, Mn), oxides and oxyhydroxides (Si, Al, Fe, Cu, Ni, Sn), phosphate (Ca, Ce, La), clay minerals (Fe, Zn, Cu, Ti) and carbonaceous material (Fe, Cu, Zn) as demonstrated by X-ray microanalysis. The solid phases are likely present in colloidal form in the dissolved fraction of the water column as well. The forms of the metals in the water column are partially due to the resuspension of bottom sediments by dredging and natural processes, to sewage outfall and to natural geochemical processes.  相似文献   

The intermittent vertical heat flux over a spruce forest canopy     

Richard H. Grant  Gary E. Bertolin  Lee P. Herrington 《Boundary-Layer Meteorology》1986,35(4):317-330

Vertical heat and momentum fluxes were measured by the eddy correlation method under near-neutral conditions during both day and night above a spruce forest canopy. Results show that 50% of the heat transported to the spruce canopy during night and away from the canopy during the day occurs in extreme magnitude events, the majority of less than one second duration. Extreme-magnitude events were more frequent and lasted longer during the day than during the night. The distributions of the duration of extreme events in the same direction as the net heat flux and the turbulence intensity for both day and night were similar.During the night, the mean horizontal windspeed was about 1 m s^-1 and the measured coincident transport of momentum and heat accounted for 36% of the total heat flux. The predominant mechanism of forced convection during the extreme nightime heat transport events was excess heat sweeps in which the duration of the event is usually less than 1 s. During the day, the mean horizontal windspeed was about 2 m s ^-1 and the measured coincident transport of momentum and heat accounted for only 16% of the total heat flux. Local free convection was suggested to account for 27% of the total heat flux. The predominant mechanism of mixed convection during the extreme daytime heat transport events is deficit heat inward interactions. During both night and day, about 10% of the total heat transport occurred in extreme events working against the thermal gradient.Now atPurdue University, West Lafayette, IN, U.S.A.  相似文献   

Occurrence,chemistry, and origin of immiscible silicate glasses in a tholeiitic basalt: A TEM/AEM study     

Lung -Chuan Kuo  Jung H. Lee  Eric J. Essene  Donald R. Peacor 《Contributions to Mineralogy and Petrology》1986,94(1):90-98

The occurrence and chemistry of immiscible silicate glasses in a tholeiite mesostasis from the Umtanum formation, Washington, were investigated with transmission electron microscopy and analytical electron microscopy (TEM/AEM). TEM observation reveals isolated, dark globules (2.1 micron or less in diameter) randomly distributed in a transparent matrix glass interstitial to plagioclase laths. The globules less than 0.3 micron and larger than 0.8 micron fall beyond the linear relationship defined by the 0.3–0.8 micron globules in a plot of the logarithm of number versus size. Large globules (0.7 micron or larger in diameter) range from homogeneous to heterogeneous in optical properties and chemistry. Homogeneous globules are completely glassy, whereas heterogeneous globules contain crystalline domains. AEM analyses show that the globules have high Si, Fe, Ca, and Ti with subordinate Mg, Al, P, S, Cl, K, and Mn, which gives high normative fa, px, il, and ap. The matrix glass consists dominantly of Si with low Al and minor Na and K, yielding a high normative qz, or, ab, and an.It is proposed that the silicate liquid immiscibility occurs by reaction of network-modifying cations (NMCs) with dominantly chain-like anionic units in the parental melt to form less polymerized, NMC-bearing units and highly polymerized, Si-rich units. The globules nucleated metastably under supercooled conditions, and medium-size globules become either larger or smaller at lower temperatures. Internal nucleation of NMC-rich phases occurred in some larger globules upon cooling.  相似文献   

Phytoplankton dynamics within Gulf Stream intrusions on the southeastern United States continental shelf during summer 1981     

James A. Yoder  Larry P. Atkinson  S. Stephen Bishop  Jackson O. Blanton  Thomas N. Lee  Leonard J. Pietrafesa 《Continental Shelf Research》1985,4(6):611-635

During July and August 1981 subsurface intrusion of upwelled nutrient-rich Gulf Stream water was the dominant process affecting temporal and spatial changes in phytoplankton biomass and productivity of the southeastern United States continental shelf between 29 and 32°N latitude. Intruded waters in the study area covered as much as 10¹ km including virtually all of the middle and outer shelf and approximately 50% of the inner shelf area.Within 2 weeks following a large intrusion event in late July, middle shelf primary production and Chl a reached 3 to 4 gC m⁻ d⁻¹ and 75 mg m⁻, respectively. At the peak of the bloom 80% of the water column primary production occurred below the surface mixed-layer, and new primary production (i.e., NO₃-supported) exceeded 90% of the total. Chl a-normalized photosynthetic rates were very high as evidenced by high mean assimilation number (15.5 mg C mg Chl a⁻¹ h⁻¹), high mean α (14 mg C mg Chl a⁻¹ Ein⁻¹ m), and no photoinhibition. As a result of the high photosynthetic rates, mean light-utilization index (Ψ) was 2 to 3 times higher than reported for temperature sub-arctic and arctic waters.The results imply a seasonal (June to August) middle shelf production of 150 g C m⁻¹, about 15% higher than previous estimates of annual production on the middle shelf. Intrusions of the scale we observed in 1981 may not occur every summer. However, when such events do occur, they are by far the most important processes controlling summer phytoplankton dynamics of the middle and outer shelf and of the inner shelf in the southern half of the study area.  相似文献   

Isolation of diagenetic overgrowths on quartz sand grains for oxygen isotopic analysis     

Mingchou Lee  Samuel M. Savin 《Geochimica et cosmochimica acta》1985,49(2):497-501

Diagenetic overgrowths on detrital quartz sand grains in sandstones can be isolated for direct measurement of their oxygen isotope ratios. Interfacial materials between detrital cores and diagenetic overgrowths are dissolved by etching with dilute HF. The weakened interface breaks when grains are agitated ultrasonically. Subsequent particle size separation is an effective means of concentrating the diagenetic component.  相似文献   

Dynamic response of twin circular tunnels due to incident SH-waves     

Thambirajah Balendra  David P. Thambiratnam  Chan Ghee Koh  Seng-Lip Lee 《地震工程与结构动力学》1984,12(2):181-201

The steady-state solution for two parallel under ground tunnels of circular cross-section subjected to incident plane harmonic SH-waves is obtained in closed form, by using the method of wave function expansion. The image technique is employed to account for the reflection of waves at the ground surface. Numerical studies are carried out to determine the influence of spacing between the tunnels on the shear stresses in concrete and steel linings.  相似文献   

Prediction of surface potential temperature over complex terrain     

H. N. Lee  W. S. Kau 《Boundary-Layer Meteorology》1984,28(1-2):79-87

Based on a statistical approach, the surface potential temperature at seven observing stations in complex terrain has been examined. It is shown that the surface potential temperature depends primarily on the rate of change of slope wind and on the geostrophic-level potential temperature.  相似文献   

Neutron and electromagnetic emissions during the 1990 May 24 solar flare     

L. G. Kocharov  Jeongwoo W. Lee  H. Zirin  G. A. Kovaltsov  I. G. Usoskin  K. R. Pyle  M. A. Shea  D. F. Smart 《Solar physics》1994,155(1):149-170

In this paper, we are primarily concerned with the solar neutron emission during the 1990 May 24 flare, utilizing the counting rate of the Climax neutron monitor and the time profiles of hard X-rays and γ-rays obtained with the GRANAT satellite (Pelaezet al., 1992; Talonet al., 1993; Terekhovet al., 1993). We compare the derived neutron injection function with macroscopic parameters of the flare region as obtained from theHα and microwave observations made at the Big Bear Solar Observatory and the Owens Valley Radio Observatory, respectively. Our results are summarized as follows: (1) to explain the neutron monitor counting rate and 57.5–110 MeV and 2.2 MeV γ-ray time profiles, we consider a two-component neutron injection function,Q(E, t), with the form $$Q(E,t) = N_f {\text{ exp[}} - E/E_f - t/T_f ] + N_s {\text{ exp[}} - E/E_s - t/T_s ],$$ whereN _f(s),E _f(s), andT _f(s) denote number, energy, and decay time of the fast (slow) injection component, respectively. By comparing the calculated neutron counting rate with the observations from the Climax neutron monitor we derive the best-fit parameters asT _f ≈ 20 s,E _f ≈ 310 MeV,T _s ≈ 260 s,E _s ≈ 80 MeV, andN _f (E > 100 MeV)/N _s (E > 100 MeV) ≈ 0.2. (2) From the Hα observations, we find a relatively small loop of length ≈ 2 × 10⁴ km, which may be regarded as the source for the fast-decaying component of γ-rays (57.5–110 MeV) and for the fast component of neutron emission. From microwave visibility and the microwave total power spectrum we postulate the presence of a rather big loop (≈ 2 × 10⁵ km), which we regard as being responsible for the slow-decaying component of the high-energy emission. We show how the neutron and γ-ray emission data can be explained in terms of the macroscopic parameters derived from the Hα and microwave observations. (3) The Hα observations also reveal the presence of a fast mode MHD shock (the Moreton wave) which precedes the microwave peak by 20–30 s and the peak of γ-ray intensity by 40–50 s. From this relative timing and the single-pulsed time profiles of both radiations, we can attribute the whole event as due to a prompt acceleration of both electrons and protons by the shock and subsequent deceleration of the trapped particles while they propagate inside the magnetic loops.  相似文献   

Geostatistical integration of MT and borehole data for RMR evaluation     

Seokhoon Oh  Hojoon Chung  Duk Kee Lee 《Environmental Geology》2004,46(8):1070-1078

The geostatistical approach was applied to integrate MT (Magneto-telluric) resistivity data and borehole information for the spatial RMR (Rock Mass Rating) evaluation. Generally, resistivity of the subsurface is believed to be positively related to the RMR, thus the resistivity and borehole RMR information was combined in a geostatistical approach. To relate the two different sets of data, the MT resistivity data were used as secondary information and the RMR mean values were estimated at unsampled points by identification of the resistivity to the borehole data. Two types of approach are performed for the estimation of RMR mean values. Then the residuals of the RMR values around the borehole sites are geostatistically modeled to infer the spatial structure of difference between real RMR values and estimated mean values. Finally, this geostatistical estimation is added to the previous means. The result applied to a real situation shows prominent improvements to reflect the subsurface structure and spatial resolution of RMR information.  相似文献