A generalized wave-activity density, which is defined as an absolute value of production of
three-dimensional vorticity vector perturbation and gradient of general potential temperature perturbation,
is introduced and its wave-activity law is derived in Cartesian coordinates. Constructed in an agoestrophic
and nonhydrostatic dynamical framework, the generalized wave-activity law may be applicable to diagnose
mesoscale weather systems leading to heavy rainfall. The generalized wave-activity density and
wave-activity flux divergence were calculated with the objective analysis data to investigate the character
of wave activity over heavy-rainfall regions. The primary dynamical processes responsible for disturbance
associated with heavy rainfall were also analyzed. It was shown that the generalized wave-activity density
was closely correlated to the observed 6-h accumulative rainfall. This indicated that the wave activity or
disturbance was evident over the frontal and landfall-typhoon heavy-rainfall regions in middle and lower
troposphere. For the landfall-typhoon rainband, the portion of generalized wave-activity flux divergence,
denoting the interaction between the basic-state cyclonic circulation of landfall typhoon and mesoscale
waves, was the primary dynamic process responsible for the evolution of generalized wave-activity density. 相似文献
We derive the cosmic energy equation for the non-point mass system of galaxies (galaxies with halos) by using the adiabatic
approximation for the growth of gravitational clustering of galaxies in the expanding Universe. The cosmic energy equation
so derived represents the general form of conservation of energy for the expanding volume. Using the derived form of cosmic
energy equation we try to study the evolution of correlation potential energy of the system. We also try to explore the condition
under which the approximation of extensivity may be applied to the infinite gravitating non-point mass system of galaxies. 相似文献
The present study aimed to quantify the water and sediment quality and growth and production parameters and to establish nutrient budgets for an average of five selected semi-intensive shrimp ponds in Bangladesh over a growing cycle. Physico-chemical parameters of water and sediments were measured and analyzed by standard methods. Gross yield (kg ha-1) of shrimp was calculated from the stocking and harvesting data. Finally, a partial nutrient mass budget for N and P was calculated. Most of the parameters of water and sediments correlated significantly with each other suggesting a high degree of interactions between different parameters in the system. Significantly higher concentrations of all species of nitrogenous nutrients were recorded in the effluent waters than that entering into the ponds. Therefore, a high loading and net output of nitrogenous nutrients in effluent waters was documented. The study also indicated a net discharge of solids and minerals through effluent loading. However, significantly lower concentrations of phosphorus in the effluent water indicated a net retention and trapping of phosphatic nutrients in the environment. Total production ranged between 532.0 and 697.0 kg ha-1 cycle-1 and P. monodon production between 484.0 and 562.0 kg ha-1 cycle-1. Ponds gained nitrogen primarily from intake water (55%) and fertilizers (29%), and nitrogen was lost primarily from water exchange (78%) and harvested shrimp (12%). Phosphorus gain occurred mostly from intake water (52%) and fertilizers (25%), and phosphorus was lost primarily from water exchange (52%) and harvested shrimp (3.3%). About 10% of input nitrogen and 44% of phosphorus were not accounted for in measured losses, and presumably were fixed or metabolized in the system. On average, 78 g N was discharged to and 25 g P was removed from the surrounding water by the system for each kilogram of shrimp produced. Mean conversion of feed nitrogen and phosphorus to shrimp flesh averaged 74% and 40%, respectively. It was concluded that semi-intensive systems serve as net supplier of N to and net remover of P from the surrounding water. 相似文献
The network-based approach to kinematic GPS positioning significantly increases the distance, over which carrier-phase ambiguity
resolution can be performed. This can be achieved either by introducing geometric conditions based on the fixed reference
locations, and/or through the use of reference network data to estimate the corrections to GPS observations that can be broadcast
to the users. The Multi Purpose GPS Processing Software (MPGPS) developed at The Ohio State University uses the multiple reference
station approach for wide area and regional differential kinematic GPS positioning. The primary processing algorithm uses
the weighted free-net (WFN) approach with the distance-dependent weighting scheme to derive optimal estimates of the user
coordinates and realistic accuracy measures. The WFN approach, combined with the single epoch (instantaneous) ambiguity resolution
algorithm is presented here as one approach to real-time kinematic (RTK) GPS. Since for baselines exceeding ~100 km, the instantaneous
ambiguity resolution may not always be possible due to the increasing observation noise and insufficient number of observations
to verify the integer selection, an alternative approach, based on a single- (or multiple-) baseline solution, supported by
a double-difference (DD) ionospheric delay propagated from the previous epoch is also presented. In this approach, some data
accumulation, supported by the network-derived atmospheric corrections, is required at the beginning of the rover data processing
to obtain the integer ambiguities; after this initialization period, the processing switches to the instantaneous RTK positioning
mode. This paper presents a discussion on the effects of the network geometry, station separation and the data reduction technique
on the final quality and reliability of the rover positioning solution. A 24-h data set of August 31, 2003, collected by the
Ohio Continuously Operating Reference Station (CORS) network was processed by both techniques under different network geometry
and reference station separation. Various solutions, such as (1) single-baseline solution for varying base-rover separation,
(2) multi-baseline solution with medium-range base separation (over 100 km), and (3) multi-baseline solution with long-range
base separation (up to 377 km), were obtained and compared for accuracy and consistency. The horizontal positioning accuracy
achieved in these tests, expressed as the difference between the estimated coordinates and the known rover coordinates, is
at the sub-decimeter level for the first approach, and at the centimeter-level for the second method, for baselines over 100 km.
In the vertical coordinate, decimeter- and sub-decimeter levels were achieved for the two approaches, respectively. Even though
all the results presented here were obtained in post-processing, both algorithms are suitable for real-time applications. 相似文献
Seismic imaging is an important step for imaging the subsurface structures of the Earth. One of the attractive domains for seismic imaging is explicit frequency–space (f – x) prestack depth migration. So far, this domain focused on migrating seismic data in acoustic media, but very little work assumed visco‐acoustic media. In reality, seismic exploration data amplitudes suffer from attenuation. To tackle the problem of attenuation, new operators are required, which compensates for it. We propose the weighted L1 ‐error minimisation technique to design visco‐acoustic f – x wavefield extrapolators. The L1 ‐error wavenumber responses provide superior extrapolator designs as compared with the previously designed equiripple L4 ‐norm and L∞‐norm extrapolation wavenumber responses. To verify the new compensating designs, prestack depth migration is performed on the challenging Marmousi model dataset. A reference migrated section is obtained using non‐compensating f – x extrapolators on an acoustic dataset. Then, both compensating and non‐compensating extrapolators are applied to a visco‐acoustic dataset, and both migrated sections are then compared. The final images show that the proposed weighted L1 ‐error method enhances the resolution and results in practically stable images. 相似文献
Saindak is one of the typical porphyry Cu deposits (PCDs) in the Chagai magmatic arc in Pakistan. Ore-forming porphyries at Saindak PCD are mainly composed of tonalite. Here, we use geochemistry of apatite enclosed in plagioclase phenocrysts from the ore-forming tonalite to constrain the releasing and recharging processes of S and Cl in the underlying parental magma chamber during PCD mineralization. Although apatite inclusions have homogeneous intra-grain S and Cl compositions, there is significant inter-grain S and Cl variations in apatite inclusions located from core to rim in the hosting plagioclase. Such inter-grain S and Cl variation in apatites are coupled with the core-to-rim trends of An, FeO and Mg contents of the hosting plagioclase phenocryst. It indicates that the Saindak PCD likely formed by episodic injection of primitive magmas during the growth of an underlying magma chamber, rather than by one major injection or by addition of mafic melt derived from different source region. Each primitive melt injection introduced essential ore-forming materials such as S and Cl, which were rapidly and effectively released to the coexisting fluids, causing mineralization. Once primitive melt injection stops, signaling the end of growth of underlying magma chamber, mineralization will cease quickly although the hydrothermal system can still survive for a long time. However, the later released fluids are relatively depleted in ore-forming materials, and thus have lower capability to generate mineralization. Accordingly, predominant porphyry-type mineralizations occurred during the growth rather than waning stage of a magmatic system.