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391.
392.
This paper proposes a numerical method to simulate oil spill trajectories, which are affected by the combination of advection, turbulent diffusion and mechanical spreading process, based on a particle tracking algorithm. Recent studies have shown that the trajectories of drifters on the ocean surface have a fractal structure that is far from being described using ordinary Brownian motion. Thus, in modeling the diffusion process, a discrete method has been employed for the generation of fractional Brownian motion (fBm) to illustrate superdiffusive transport. The algorithm is implemented to predict oil slick trajectories following the “Arteaga” oil spill accident that occurred near the Dalian coastal region in 2005. When compared with the observed data and the results of traditional diffusion modeling, the numerical results based on the fBm model are encouraging. 相似文献
393.
The success of transient storage (TS) modeling for natural streams depends, in part, on the ability to describe the dispersion process accurately. Evidence based on stream tracer data shows that solute transport processes often do not follow the classical second-order dispersion model (e.g., early breakthrough and faster than Fickian travel times were observed). While models based on space-fractional dispersion are a promising alternative, different definitions of fractional derivatives exist in the literature. Unlike integer-order derivatives, fractional derivatives represent convolutions of concentration with long-range spatial correlation and numerical approximations can produce dense matrices. Therefore issues of both accuracy and computational efficiency need to be examined to successfully identify model parameters for natural streams. In this paper, we first compare the performance of several numerical approaches for solving the space-fractional dispersion equation. We examine three different numerical approaches to approximate the space-fractional derivatives including: (a) a fully-implicit scheme based on the shifted Grünwald–Letnikov (GL) approximation (b) a three-point implicit representation based on the GL formula and (c) a three-point implicit scheme based on mass conservation and the Caputo definition of the fractional derivative. We then use an operator-splitting technique to evaluate a TS model based on space-fractional dispersion (the FSTS model) and test the model against analytical solutions and stream tracer data. A sequence acceleration method (Richardson extrapolation) significantly improves the performance of all schemes examined. Results indicate that the fully-implicit GL method with Richardson extrapolation produces the most accurate solutions while the three-point implicit GL scheme has a stringent time-step restriction to produce acceptable solutions. The three-point implicit scheme based on the Caputo derivative produces accurate solutions in a fraction of the time taken by the fully-implicit GL method and represents the best trade-off between accuracy and computational efficiency for practical applications. The scheme is suitable for parameter estimation and is used to successfully describe tracer data in a natural stream. 相似文献
394.
395.
分别以粉煤灰、煤矸石、红柱石千枚岩、油页岩渣等富硅铝矿石为原料,经过除杂、煅烧活化后,利用水热晶化法制备出纳米莫来石复相粉体。采用X射线粉末衍射(XRD)、透射电子显微镜(TEM)、能量色散X射线荧光光谱分析(EDX)和选区电子衍射(SAED)等手段研究了复相粉体的物相组成与显微结构,并用魔角旋转核磁(MAS~NMR)分析水热晶化反应机理。结果表明:经过一定温度煅烧活化后,当NaOH溶液浓度为2~3 mol/L、搅拌温度80~90℃、恒温3 h、液固比为10 mL/g时,上述四种原料均可制得以莫来石为主晶相的纳米复相粉体,其中以煤矸石、红柱石千枚岩、油页岩渣为原料制备的晶体均为结晶良好的柱状晶,平均长度分别为50、300和150 nm,平均长径比分别为4、3.5和3.75;以粉煤灰为原料制备的晶体主要呈现棒状、针状和纤维状,其棒状晶长度约30~80 nm、直径约4.5~30 nm。 相似文献
396.
LI Xuejun LUO Zhaohu LI Xiaowei WANG Yu YANG Zongfeng LI Jie LIU Xiao 《《地质学报》英文版》2020,94(5):1428-1439
The Panzhihua layered intrusions is generated closely related to the Emeishan LIPs. This paper analyzes the spatial distribution of plagioclase and pyroxene. The quantitative texture analysis of 2209 plagioclase shows that the characteristic length of plagioclase is 0.54 to 0.96 mm, the intercept variation range is large, from ?0.67 to 0.96, and the slope is ?1.85 to ?1.04, the Aspect Ratio shows from 1.84 to 2.59 and fractal dimension D is 1.908–1.933. The quantitative texture analysis of 2342 pyroxene shows that the characteristic length of pyroxene is 0.38–0.64 mm, the intercept shows from 0.46 to 2.26, The slope ranges from ?2.6 to ?1.47, the Aspect Ratio value varies from 1.53 to 1.71, the fractal dimension D is 0.93 to 1.13. All the CSDs results of the Panzhihua intrusions indicate that plagioclase and pyroxene form in an open magma system and undergo four replenishment of magma injection. The plagioclase crystals do not grow as the lathlike shape, and the fractal growth leads to complex crystal surface. The plagioclase undergoes deformation compaction during the crystal process, and then is oriented. The pyroxene crystals grow along an approximately triaxial ratio and undergo texture adjustment and small crystal dissolution reabsorption. When all crystals in magma system grows up to 2 mm, the pyroxene undergoes cumulation in the Panzhihua layered intrusions. The plagioclase crystallization time scale is 171.23–304.41 years, representing that the crystallization is the more uniform in central part of the melt. The nucleation density continuously increases during the crystallization process of the magma system. The time scale to reach the final maximum crystal nucleation density is 15.28–58.98 years. 相似文献
397.
藏南羊卓雍错流域水化学主离子特征及其控制因素 总被引:14,自引:1,他引:13
水化学主离子特征是流域湖泊的一个重要特征,对气候以及河流所经地区的环境具有指示作用.本文对藏南羊卓雍错流域水化学主离子组成特征及其控制因素进行分析,结果显示流域内不同水体(湖水、河水、地下水)之间的主离子组成以及水化学类型差异显著.其中,羊卓雍错的水化学类型为SO24--HCO3--Mg2+-Na+,巴纠错为SO24--Mg2+-Na+,沉错为SO24--Na+-Mg2+-Ca2+,普莫雍错为HCO3--SO24--Mg2+-Ca2+,空姆错为HCO3--SO24--Ca2+;流域河水中主要阴离子为HCO3-和SO24-,Ca2+为绝对优势阳离子;流域地下水化学类型则为HCO3--Ca2+.究其原因,流域水体化学组成主要受岩石风化作用控制;除此,羊卓雍错、巴纠错和沉错水化学组成亦受自身蒸发-结晶作用的影响.就入湖河水而言,羊卓雍错入湖河水整体受碳酸盐岩石风化的影响较大,蒸发岩溶解的影响次之;沉错和空姆错入湖河流(卡鲁雄曲)的蒸发岩来源则略大于碳酸盐岩来源;而硅酸盐对流域内河水的水化学性质影响较小.与入湖河水相比,羊卓雍错和沉错湖水的Mg2+、Na+和SO24-含量较高,而Ca2+和HCO3-含量较低.这应该与湖水蒸发强烈使得湖水中Ca2+和HCO3-析出并沉积到湖底有关.而空姆错由于湖泊面积小、入湖河水流量大,致使其湖水与入湖河水的主离子组成差异不显著. 相似文献
398.
Surface Acidity of Amorphous Aluminum Hydroxide 总被引:3,自引:0,他引:3
K. FUKUSHI K. TSUKIMURA H. YAMADA 《《地质学报》英文版》2006,80(2):206-211
The surface acidity of synthetic amorphous AI hydroxide was determined by acid/base titration with several complementary methods including solution analyses of the reacted solutions and XRD characterization of the reacted solids. The synthetic specimen was characterized to be the amorphous material showing four broad peaks in XRD pattern. XRD analyses of reacted solids after the titration experiments showed that amorphous AI hydroxide rapidly transformed to crystalline bayerite at the alkaline condition (pH〉10). The solution analyses after and during the titration Ksp=^aAl^3+/aH^+^3 ,was 10^10.3. The amount of consumption of added acid or base during the titration experiment was attributed to both the protonation/deprotonation of dissolved AI species and surface hydroxyl group. The surface acidity constants, surface hydroxyl density and specific surface area were estimated by FITEQL 4.0. 相似文献
399.
Random noise has a negative impact on seismic-prospecting record processing. An important step to improve the methods aimed at the attenuation of random noise is to scientifically characterize the properties of the noise. Numerical modeling is useful to understand the nature of the random noise. In this study, we present a Brownian-motion-based parametric modeling algorithm for the simulation of seismic-prospecting random noise in the desert. The optimal Hurst exponent required to implement the method can be determined by comparing the spectral properties related to the noise data and the simulated results. The data used to analyze the properties of the noise were acquired in the Tarim Basin (Northwest of China). We verify the performance of the modeling algorithm by comparing the results obtained after the simulation with the real noise data in both the time domain and the spatio-temporal domain. The experimental results thus obtained prove the accuracy and efficiency of the proposed modeling algorithm. This study can be used as a basis to investigate the seismic-prospecting random noise characteristics and thus contribute to its mitigation. 相似文献
400.
Geochemical and Sr–Nd isotopic constraints on the petrogenesis of the Goesan monzodiorite pluton in the central Okcheon belt,Korea
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The Permian–Triassic high pressure metamorphism and potassic magmatism in central Korea attest to the extension of the Dabie‐Sulu collision belt in central‐eastern China towards the Korean Peninsula and possibly the Japanese Islands. We present major and trace element and Sr–Nd isotope data for a ca. 230 Ma monzodiorite pluton emplaced in the Goesan area, central Okcheon belt, Korea. This pluton shows geochemical features comparable with those of the coeval monzonite–syenite–gabbro–mangerite suite documented recently in the Gyeonggi massif. The metaluminous and alkali–calcic signatures of the Goesan intrusives correspond to the Caledonian‐type post‐orogenic granitoids. The K2O/Na2O ratios of all analyzed samples are greater than 1, and are not correlative with their SiO2 contents. The enrichment of both large‐ion‐lithophile elements and highly compatible elements in the Goesan pluton is probably indicative of metasomatized mantle origin. The elemental fractionation in the source region must have occurred in the distant past, possibly the Paleoproterozoic, to generate significantly negative εNd(t) values (< –16). Chondrite‐normalized rare earth element patterns as well as Rb/Sr and Ba/Rb ranges suggest that the source consists of amphibole‐bearing rocks. Progressive decreases in negative Eu anomaly and Ba, Sr, Ni, Cr and V contents with increasing SiO2 contents reflect an important role of plagioclase, biotite and hornblende for the fractionation process. Zr is undersaturated in the potassic, metaluminous melt. The initial Sr–Nd isotopic compositions of the samples are correlated with their SiO2 contents, substantiating a role of crustal assimilation during the magmatic differentiation. The Sr–Nd elemental and isotopic modeling suggests that the Goesan pluton was initially slightly heterogeneous in its isotopic composition, and underwent concurrent assimilation and fractional crystallization. The occurrence of the Goesan pluton provides further evidence corroborating the amalgamation of allochthonous terranes within the Okcheon belt during the Permian–Triassic collisional orogeny. 相似文献