157,987 research outputs found

    Kinetic kd-Trees and Longest-Side kd-Trees

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    We propose a simple variant of kd-trees, called rank-based kd-trees, for sets of points in~RealsdReals^d. We show that a rank-based kd-tree, like an ordinary kd-tree, supports range search que-ries in~O(n11/d+k)O(n^{1-1/d}+k) time, where~kk is the output size. The main advantage of rank-based kd-trees is that they can be efficiently kinetized: the KDS processes~O(n2)O(n^2) events in the worst case, assuming that the points follow constant-degree algebraic trajectories, each event can be handled in~O(logn)O(log n) time, and each point is involved in~O(1)O(1) certificates. We also propose a variant of longest-side kd-trees, called rank-based longest-side kd-trees (RBLS kd-trees, for short), for sets of points in~Reals2Reals^2. RBLS kd-trees can be kinetized efficiently as well and like longest-side kd-trees, RBLS kd-trees support nearest-neighbor, farthest-neighbor, and approximate range search queries in~O((1/epsilon)log2n)O((1/epsilon)log^2 n) time. The KDS processes~O(n3logn)O(n^3log n) events in the worst case, assuming that the points follow constant-degree algebraic trajectories; each event can be handled in~O(log2n)O(log^2 n) time, and each point is involved in~O(logn)O(log n) certificates

    Adsorption of 2,4-Dichlorophenoxyacetic Acid onto Volcanic Ash Soils:

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    The quantification of the linear adsorption coefficient (Kd) for soils plays a vital role to predict fate and transport of pesticides in the soil-water environment. In this study, we measured Kd values for 2,4-Dichlorophenoxyacetic acid (2,4-D) adsorption onto Japanese volcanic ash soils with different amount of soil organic matter (SOM) in batch experiments under different pH conditions. All measurements followed well both linear and Freundlich adsorption isotherms. Strong correlations were found between measured Kd values and pH as well as SOM. The 2,4-D adsorption increased with decreasing pH and with increasing SOM. Based on the data, a predictive Kd equation for volcanic ash soils, log (Kd) = 2.04 - 0.37 pH + 0.91 log (SOM), was obtained by the multiple regression analysis. The predictive Kd equation was tested against measured 2,4-D sorption data for other volcanic ash soils and normal mineral soils from literature. The proposed Kd equation well predicted Kd values for other volcanic ash soils and slightly over- or under-predicted Kd values for normal mineral soils. The proposed Kd equation performed well against volcanic ash soils from different sites and countries, and is therefore recommended for predicting Kd values at different pH and SOM conditions for volcanic ash soils when calculating and predicting 2,4-D mobility and fate in soil and groundwater

    Kinetic kd-trees

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    We propose a simple variant of kd-trees, called rankbased kd-trees, for sets of points in Rd. We show that a rank-based kd-tree, like an ordinary kd-tree, supports range search queries in O(n1-1/d + k) time, where k is the output size. The main advantage of rank-based kd-trees is that they can be efficiently kinetized: the KDS processes O(n2) events in the worst case, assuming that the points follow constantdegree algebraic trajectories, each event can be handled in O(log n) time, and each point is involved in O(1) certificates

    Distribution coefficients for chemical components of a coal-oil/water system

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    Distribution coefficients (KDS) were measured by equilibrating a coal oil comparative reference material (CRM-1) with water and then separating the oil and water phases. Aqueous phase concentrations were determined by direct analysis of this phase, while organic phase concentrations were determined from the original oil composition by difference. The log KD values obtained for acidic and basic components were generally KD and log Sw (water solubility), and between log KD and log KD and log Kow (octanol/water partition coefficient). Alkylated benzenes had significantly higher KDS than did unsubstituted aromatics of similar molecular weight. Examination of homologs revealed an increase of 0.307 log KD units per additional carbon atom for polynuclear aromatic hydrocarbons having from 10 to 16 carbons. Alkyl substituent effects determined for various sets of homologs ranged from 0.391 to 0.466 log Kd units per--CH2--group added.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/27171/1/0000168.pd

    On the logarithmic comparison theorem for integrable logarithmic connections

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    Let X be a complex analytic manifold, D ⊂ X a free divisor with jacobian ideal of linear type (e.g. a locally quasi-homogeneous free divisor), j : U = X − D ֒→ X the corresponding open inclusion, E an integrable logarithmic connection with respect to D and L the local system of the horizontal sections of E on U. In this paper we prove that the canonical morphisms Ω • X(log D)(E(kD)) −→ Rj∗L, j!L −→ Ω • X(log D)(E(−kD)) are isomorphisms in the derived category of sheaves of complex vector spaces for k ≫ 0 (locally on X).Ministerio de Educación y CienciaFondo Europeo de Desarrollo Regiona

    Spatial Variability of Radionuclide Distribution Coefficients at the Savannah River Site and the Sub-surface Transport Implications

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    Distribution coefficients, Kd, were measured for a suite of gamma-emitting radionuclides in uncontaminated soils from the E-Area burial grounds at the Savannah River Site. The objectives of the study were to (1) characterize the spatial variability of Kd, (2) evaluate the effect of spatial variability on vadose zone transport, and (3) develop statistical models for predicting Kd from physical or chemical characteristics. Equilibrium batch sorption tests were performed on 27 soil samples collected from depths ranging from 11 ft to 100 ft from the BGO-3A core with 241Am, 109Cd, 139Ce, 137Cs, 57Co, 60Co, 203Hg, 85Sr, and 88Y. Distribution coefficients were calculated from solid and aqueous phase concentrations measured by gamma spectroscopy. Graphical and statistical analyses were performed on Kd distributions for the entire data set and for three stratified samples: the upper vadose zone, the lower vadose zone, and the aquifer zone. The effect of Kd variability on vadose zone transport was assessed by comparing calculated transport times for three deterministic transport models to a stochastic calculation of vadose zone transport time. The impact of Kd variability on stochastic vadose zone transport was based on a Monte Carlo analysis utilizing the distributions of Kd for each isotope. Finally, SAS regression was utilized to develop statistical correlation models for predicting Kd from soil characterization parameters. The Kd values were generally ranked as follows: 88Y \u3e\u3e 57, 60Co \u3e 109Cd \u3e 203Hg \u3e 137Cs \u3e\u3e 85Sr. Insufficient data were generated for 241Am and 139Ce to be included in this trend analysis. Also, Kd values were generally greatest in the aquifer zone followed by the upper vadose zone with the lower vadose zone generally exhibiting the lowest Kd values. Variability in the Kd values generally followed this same trend. In terms of the distributions of Kd values, when the BGO-3A core was taken as a whole all of the examined isotopes were most closely log-normally distributed. When the core was stratified into the three zones described above, differences in the distributions were noted. In the upper vadose zone, the isotopes with higher Kd values (109Cd, 57,60Co, and 88Y) were most nearly normally distributed while those with lower Kd values were either log-normally distributed or could not be characterized. In the lower vadose zone all of the isotopes were most closely normally distributed. Finally, in the aquifer zone, cadmium and strontium were log-normally distributed while the distribution for yttrium was characterized as normal. The remaining isotopes could not be characterized in the aquifer zone. Based on the Monte Carlo analysis, it was noted that all of the travel time distributions were log-normal with truncated tails. Transport times for the relative concentration of C/C0 = 0.5 were about three times as long as those measured for the C/C0 = 0.01 level and about one-third the length of the C/C0 = 0.99 travel times for each of the isotopes. It was also observed that isotopes with higher Kd values (specifically americium, cerium, and yttrium) displayed much greater differences between the transportation times required to reach the C/C0 = 0.5 level and the times required to reach the 0.01 and 0.99 levels. These differences decreased in magnitude with decreasing Kd values. Viable prediction models were developed for 137Cs, 57Co, 60Co, and 85Sr that were capable of accounting for about 70% or more of the variability observed in Kd for those isotopes. Models which could explain only about 55% of Kd variability were developed for 109Cd and 203Hg. These models were more suited as a first approximation for Kd estimation. All of the developed models generally utilized the expected geochemical variables based on the literature. Aluminum, iron, and titanium content were significant factors in the final statistical model for 109Cd Kd values. For 137Cs Kd values, the primary factors affecting sorption were CEC and clay content. For cobalt sorption, aluminum, iron, and titanium content confirmed the dependence on complexing ions. Mercury sorption correlated with CEC, aluminum, and iron content. Finally, CEC was shown to be the most significant factor for modeling strontium sorption
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