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11.
PEI Xiandeng KONG Lingwang ZHU Yuanhong HUANG Hao 《地球空间信息科学学报》2005,8(4):306-310
IntroductionIn color reproduction and communication, met-amer exists inherently when the conventionalcondition matching used. Therefore , the colordifference introduced makes the accuracy of colorrepresentation be lowered.In order to eli minatemetamer CIE developed the scheme so-calledspectra matching in Publication 15 .2 and speci-fied that using band-pass filters with 5 nminter-val to sample and then reconstruct the originalcolor signal ,thus the color difference will disap-pear[1].Spectra… 相似文献
12.
Graça Cabeçadas M. José Brogueira M. Gelena Cavaco Célia Gonçalves 《Journal of Oceanography》2010,66(2):201-210
Although the circulation of intermediate water masses in the eastern North Atlantic remains poorly defined, the presence of
fresher intermediate waters, the Sub-Artic (SAIW) and the Antarctic Intermediate Water (AAIW), as well the saline intermediate
Mediterranean Water (MW), has been tracked using biogeochemical properties. Here we assess the hydrographic and chemical structures
of intermediate waters along the western Portuguese margin by examining the vertical distributions and property-property plots
of chemical tracers (oxygen and nutrients). AAIW was traced by low oxygen and high nutrients, while SAIW was recognized by
low nutrients. The Mediterranean Water (MW) undercurrent is shown to spread towards the eastern flank of Gorringe bank. Concurrently,
the fresher waters gained salt by direct incorporation of MW, while this water was enriched in nutrients on its way northward
and westward owing, to a great extent, to the entrainment of an AAIW branch. The distributions of nutrients and apparent oxygen
utilization are discussed in terms of regional ocean circulation. Our analysis suggests a circulation pattern of the various
intermediate waters along the western Portuguese margin: MW extends all over the area, but its presence is more pronounced
around cape St. Vincent; SAIW apparently moves southward, reaching the Gorringe bank region, and AAIW flows northward along
the coast and around the bank. 相似文献
13.
Subsidence of organic soils in the Sacramento-San Joaquin Delta threatens sustainability of the California (USA) water supply system and agriculture. Land-surface elevation data were collected to assess present-day subsidence rates and evaluate rice as a land use for subsidence mitigation. To depict Delta-wide present-day rates of subsidence, the previously developed SUBCALC model was refined and calibrated using recent data for CO2 emissions and land-surface elevation changes measured at extensometers. Land-surface elevation change data were evaluated relative to indirect estimates of subsidence and accretion using carbon and nitrogen flux data for rice cultivation. Extensometer and leveling data demonstrate seasonal variations in land-surface elevations associated with groundwater-level fluctuations and inelastic subsidence rates of 0.5–0.8 cm yr–1. Calibration of the SUBCALC model indicated accuracy of ±0.10 cm yr–1 where depth to groundwater, soil organic matter content and temperature are known. Regional estimates of subsidence range from <0.3 to >1.8 cm yr–1. The primary uncertainty is the distribution of soil organic matter content which results in spatial averaging in the mapping of subsidence rates. Analysis of leveling and extensometer data in rice fields resulted in an estimated accretion rate of 0.02–0.8 cm yr–1. These values generally agreed with indirect estimates based on carbon fluxes and nitrogen mineralization, thus preliminarily demonstrating that rice will stop or greatly reduce subsidence. Areas below elevations of –2 m are candidate areas for implementation of mitigation measures such as rice because there is active subsidence occurring at rates greater than 0.4 cm yr–1. 相似文献
14.
Kieran P. Donaghy 《Journal of Geographical Systems》2011,13(1):17-30
In the literatures of regional science, urban economics, and urban development planning, a working assumption is that individuals
respond to incentives and regulations, given their preferences. Models for planning and policy analyses are used to consider
what might occur if the incentives or regulations were different. In these models, however, preferences are usually assumed
to be given and stable, and agents are usually assumed to be homogeneous. This paper focuses on the implications of making
preferences in models of policy implementation endogenously determined and time varying heterogeneous agents. We consider
first the recent literature on intertemporal choice and preference change, which cuts across many disciplines, and more briefly
the literature on norm-regarding behavior. We then elaborate a simple model of transportation demand—from a static to a dynamic
orientation, from fixed and exogenously given preferences of strictly self-regarding agents to endogenously determined and
policy-induced preferences of heterogeneous agents—and illustrate its characteristics with simple numerical examples. 相似文献
15.
Weidong Sun Jin-tuan Wang Li-peng Zhang Chan-chan Zhang He Li Ming-xing Ling Xing Ding Cong-ying Li Hua-ying Liang 《中国地球化学学报》2017,36(1):9-15
Copper is a moderately incompatible chalcophile element. Its behavior is strongly controlled by sulfides. The speciation of sulfur is controlled by oxygen fugacity. Therefore, porphyry Cu deposits are usually oxidized (with oxygen fugacities > ΔFMQ +2) (Mungall 2002; Sun et al. 2015). The problem is that while most of the magmas at convergent margins are highly oxidized, porphyry Cu deposits are very rare, suggesting that high oxygen fugacity alone is not sufficient. Partial melting of mantle peridotite even at very high oxygen fugacities forms arc magmas with initial Cu contents too low to form porphyry Cu deposits directly (Lee et al. 2012; Wilkinson 2013). Here we show that partial melting of subducted young oceanic slabs at high oxygen fugacity (>ΔFMQ +2) may form magmas with initial Cu contents up to >500 ppm, favorable for porphyry mineralization. Pre-enrichment of Cu through sulfide saturation and accumulation is not necessarily beneficial to porphyry Cu mineralization. In contrast, re-melting of porphyritic hydrothermal sulfide associated with iron oxides may have major contributions to porphyry deposits. Thick overriding continental crust reduces the “leakage” of hydrothermal fluids, thereby promoting porphyry mineralization. Nevertheless, it is also more difficult for ore forming fluids to penetrate the thick continental crust to reach the depths of 2–4 km where porphyry deposits form. 相似文献
16.
The application of the saddlepoint approximation to reliability analysis of dynamic systems is investigated. The failure event in reliability problems is formulated as the exceedance of a single performance variable over a prescribed threshold level. The saddlepoint approximation technique provides a choice to estimate the cumulative distribution function (CDF) of the performance variable. The failure probability is obtained as the value of the complement CDF at a specif ied threshold. The method requires computing the saddlepoint from a simple algebraic equation that depends on the cumulant generating function (CGF) of the performance variable. A method for calculating the saddlepoint using random samples of the performance variable is presented. The applicable region of the saddlepoint approximation is discussed in detail. A 10-story shear building model with white noise excitation illustrates the accuracy and effi ciency of the proposed methodology. 相似文献
17.
The Ocean Drilling Program (ODP) initiated drilling at Site 1256D in the Guatemala Basin, about 1,000 km off the East Pacific
Rise to penetrate plutonic rocks, anticipated to be relatively shallow in this region, formed at an ultra-fast spreading rate.
IODP Expedition E312 successfully drilled into gabbros at ~1,150 m in basement. Multi-channel seismic traces show weak laterally
coherent sub-basement reflections at borehole depths. Synthetic reflectivity seismograms were computed using a Ricker wavelet
and impedance profiles from borehole sonic logs. These seismograms show significant sub-basement amplitude peaks. A zero-offset
vertical seismic profile, shot on E312, was processed to investigate the authenticity of these reflections and their relationship
to borehole geology. A dual scheme of the median filtering and F–K dip filtering was used. Tests with synthetic seismograms
indicate the approach is effective at reasonable SNR levels. Downgoing energy is clearly identified but negligible upgoing
energy is visible over random noise. These results indicate that lava flows and igneous contacts in upper ocean crust have
significant topography on lateral scales less than the Fresnel Zone (~300 m) due to igneous and tectonic processes. 相似文献
18.
19.
Eugene Yee 《Boundary-Layer Meteorology》2001,98(3):517-527
A simple analytical model is developed for the meanupcrossing rate of plume concentration fluctuations assuming that thisprocess can be well approximated by a lognormal process. The resultingexpression requires only the specification of the in-plume fluctuationintensity and in-plume Taylor micro-time scale and, hence, does notexplicitly involve the joint probability density function of theconcentration and its derivative. The analytical model provides agood fit to some field measurements of the mean upcrossing rate ina dispersing plume. 相似文献
20.
This study analyzed the uncertainty of inversion and the resolution limit in the presence of noise by means of statistical experiments. The exhaustive method is adopted to obtain the global optimal solution in each experiment. We found that even with small level of noise, solutions fluctuate in a large range for the thin bed. The distribution of solutions in the presence of noise is closely related to the spread of the cost function in the absence of noise. As a result, the area of a certain neighborhood around the true solution on the spread of the cost function in the absence of noise is used to evaluate the uncertainty of inversion and the resolution limit in the presence of noise. In the case that the SNR (signal-to-noise ratio) is 5 in this study, solutions focus around the true solution with a very small uncertainty only when the bed thickness is greater than the reciprocal of the double predominant frequency of the convoluting wavelet. 相似文献