Ks Processes Research Articles

Factors controlling saturated hydraulic conductivity along a typical black soil slope

Saturated hydraulic conductivity (Ks) is controlled by a suite of soil processes operating at various scales. Little is known about the spatial variability of Ks along a slope and how it is changed through the planting operation process and the specific scales at which the controlling factors function. The objective was to characterize the scale-dependent relationships between Ks and various soil processes and thereby to identify the primary controlling factors of Ks. On a typical slope transect of 900 m in the black soil region of Northeast China, Ks and six soil properties of bulk density (BD), wet-aggregate stability (WAS), surface roughness (SR), soil organic carbon content, sand and clay contents were investigated in an interval of 20 m before and after mechanical sowing in the spring. Statistical correlation analysis, its combination with noise-assisted multivariate empirical mode decomposition (NA-MEMD) and wavelet coherence were employed to examine the interactions between Ks and each factor at different spatial scales. The BD was admittedly the dominant factor controlling Ks, followed by WAS and SR before and after sowing, respectively. The statistical correlation analysis only detected the significant interactions between Ks and BD, whereas the essential influence of WAS and SR were revealed upon frequency component decompositions by NA-MEMD and biwavelet coherency. Applying multiple wavelet coherence, BD was believed adequate in explaining Ks variability before sowing, whereas the combination of BD and SR was suggested in the case after sowing. These findings hold important implications for precise Ks estimations in the black soil region of Northeast China as well as other similar regions, and also demonstrate the effectiveness of NA-MEMD and wavelet coherence in untangling complex scale-dependent relationships among soil processes.

Noise‐Assisted Multivariate Empirical Mode Decomposition of Saturated Hydraulic Conductivity along a South‐North Transect across the Loess Plateau of China

Core Ideas Ks and eight associated factors were decomposed into different scales using NA‐MEMD. Small‐scale variations of Ks were dominated by soil properties, especially bulk density. Large‐scale Ks variations were mainly controlled by topographic and climatic factors. Summing up MLR estimates of Ks scale components surpassed MLR estimation of Ks before NA‐MEMD. Saturated hydraulic conductivity (Ks) usually varies at multiple scales in space, as affected by different soil and environmental processes operating at diverse scales. Identifying spatial process relationships can be challenging due to overlapping of underlying processes at different scales. The objective of this study was to evaluate noise‐assisted multivariate empirical mode decomposition (NA‐MEMD) for characterizing Ks variability and depicting its scale‐dependent relationships with different soil properties and environmental factors. At an interval of 10 km along an 860‐km south‐north transect across the Loess Plateau of China, Ks, bulk density, soil organic carbon content, sand and clay contents at three depths of 0 to 10, 10 to 20 and 20 to 40 cm were investigated as well as four environmental factors of elevation, slope gradient, annual precipitation and temperature. Decomposed into different intrinsic mode functions (IMFs) and residues by NA‐MEMD, Ks at all depths were found to vary at the smallest scale of 29 km mainly, corresponding to IMF1s, which manifested 33.0 to 48.1% of the total Ks variance. The small‐scale variations of Ks reflected not only in IMF1s but also in IMF2s and IMF3s were dominated by soil properties especially bulk density, and the large‐scale variations corresponding to IMF4s and IMF5s were controlled by environmental factors in general. For each depth, Ks at the scale of investigation was estimated by adding all the IMFs and residue derived from the factor components at equivalent scales using multiple linear regression (MLR). Such Ks estimations after NA‐MEMD evidently outperformed the MLR before NA‐MEMD by explaining additional 9.4 to 18.7% of the total Ks variance, but underperformed the artificial neural network and state‐space approach also implemented on undecomposed spatial series of Ks and its underlying factors. NA‐MEMD serves as a useful tool for Ks characterization and its incorporation with nonlinear functions or spatial interactions with impact factors is suggested for the estimation of Ks and other soil processes.

Effect of gas flow rate on deposition behavior of Fe-based amorphous alloys in vacuum kinetic spray process

Amorphous Fe-based coatings were fabricated on soda–lime glass substrates by the vacuum kinetic spray (VKS) method. The effects of gas flow rate on the deposition behavior, the coating microstructure, and properties were investigated. The deposition mechanism of bulk metallic glass (BMG) material was also analyzed. The as-fabricated film microstructure was studied by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and high resolution transmission electron microscopy (TEM). Moreover, atomic force microscopy (AFM) and a scratch tester were used to measure the surface roughness and cohesive/adhesive bonding strength, respectively. The deposition rate was drastically increased as the gas flow rate increased, and the film was significantly thicker than that of ceramics. Also, the particles underwent more severe deformation and fragmentation as the particle velocity increased, similar to a ceramic material. However, interestingly, a porous film was fabricated in contrast to a ceramic film, and the porosity increased with increasing gas flow rate. It is thought that the cohesive bonding strength was constant regardless of gas flow because of the porous coating layer, while adhesive strength significantly increased by an anchoring layer as the gas flow increased. Based on the fact that no crystalline phases except for ZrO2 were found in the coating layer, fragmentation is still an important process for successful deposition in a VKS system compared to the KS process. As a result, it can be concluded that the plasticity-accompanied fragmentation process of BMG particles resulted in a porous coating layer in contrast to the dense ceramic coating formed by the fragmentation-dominant deposition process.

Lack of the neighboring group rate effect in solvolytic reactions that proceed via participation

AbstractIn order to investigate the influence of solvent polarity on the rate effect of double bonds in reactions that proceed via an extended π‐participation mechanism, the solvolysis rates (kU) of the benzyl chloride derivative 1 and tertiary chloride 2 that have doubly unsaturated side chains were measured in absolute ethanol, 80% v/v. aq. ethanol and 97% wt. aq. trifluoroethanol. The rates of the corresponding saturated analogs 1S and 2S (kS) were measured in 80% aq. ethanol and 97% wt. aq. trifluoroethanol, while those in pure ethanol were calculated according to LFER equation log k = sf (Ef + Nf). In solvents with moderate ionizing power (ethanol and 80% aq. ethanol) the expected rate effects were obtained (kU/kS>1), while in solvent with high ionizing power (2,2,2‐trifluoroethanol) absence of the rate effect was observed (kU/kS≈1), indicating that in the kS process the solvation of the transition state is very important, while in kΔ process the breaking of the CCl bond is not appreciably developed in the transition state and the solvent effect is marginal. Copyright © 2007 John Wiley & Sons, Ltd.

SUPERSYMMETRIC CONTRIBUTIONS TO THE CP ASYMMETRY OF THE B→ϕKS AND B→η'KS

We analyse the CP asymmetry of the B→ϕKS and B→η'KS processes in general supersymmetric models. We consider both gluino and chargino exchanges in a model-independent way by using the mass insertion approximation method. We adopt the QCD factorization method for evaluating the corresponding hadronic matrix elements. We show that chromomagnetic type of operator may play an important role in accounting for the deviation of the mixing CP asymmetry between B→ϕKS and B→J/ψKS processes observed by Belle and BaBar experiments. We also show that due to the different parity in the final states of these processes, their supersymmetric contributions from the R-sector have an opposite sign, which naturally explain the large deviation between their asymmetries.

Substituent Effects. XVI. Acetolysis of 2-Phenylethyl Tosylates

Abstract The acetolysis rates of 2-arylethyl tosylates were determined for a series of aryl substituents. The non-linear substituent effect was reasonably accounted for on the basis of two linear LArSR relationships; one for the aryl-assisted (FkΔ) and one for the unassisted (ks) processes, respectively. A precise dissection of the apparent substituent effect into individual effects for both processes was achieved in this manner. The substituent effect on the ks process can be described as a linear function of σ° with a small ρs of −0.19, and that on the FkΔ process in terms of the LArSR Eq., with ρΔ=−3.87 and an rΔ=0.631. The use of σ+ for the FkΔ process failed to give any reasonable dissection. The r value for this FkΔ process is essentially identical to that for the neophyl solvolysis. The unique r value of 0.6 is concluded to be characteristic of β-arylassisted ionization processes in general.

ChemInform Abstract: POLAR SUBSTITUENT EFFECTS IN THE SOLVOLYSIS OF PRIMARY AND TERTIARY ALKYL HALIDES. POLAR EFFECT. IX

When the Hammett-Taft equation log (k/ko)=ρq · σ is applied to the solvolysis of the 3-substituted propyl bromides 6a-6i in ethanol/water 4:1 (v/v) log k correlates linearly with σ except in cases where R exerts an anchimeric effect. The reaction constant ρq for 6 is − 0.12 and is typical for a nucleophilic solvent-assisted ks process at a primary C-atom. The tertiary halides 1 and 3, however, which react with little or no nucleophilic solvent assistance, i.e. by kc processes, lead to larger ρq values of −0.71 and −1.14, respectively. The reaction constant pq is therefore a sensitive gauge for charge development in the transition state for solvolysis of saturated compounds.

Polar Substituent Effects in the Solvolysis of Primary and Tertiary Alkyl Halides. Polar Effect IX

AbstractWhen the Hammett‐Taft equation log (k/ko)=ρq · σ is applied to the solvolysis of the 3‐substituted propyl bromides 6a‐6i in ethanol/water 4:1 (v/v) log k correlates linearly with σ except in cases where R exerts an anchimeric effect. The reaction constant ρq for 6 is − 0.12 and is typical for a nucleophilic solvent‐assisted ks process at a primary C‐atom. The tertiary halides 1 and 3, however, which react with little or no nucleophilic solvent assistance, i.e. by kc processes, lead to larger ρq values of −0.71 and −1.14, respectively. The reaction constant pq is therefore a sensitive gauge for charge development in the transition state for solvolysis of saturated compounds.

Solvolysis in Carboxamides. V. Solvolytic Elimination of threo-1-Methyl-2-phenylpropyl Brosylate in N,N-Dimethylacetamide. Kinetic, Product, and Deuterium Tracer Studies

Abstract Solvolysis of a series of ring substituted threo-1-methyl-2-phenylpropyl brosylates has been carried out in N,N-dimethylacetamide (DMA) as solvent. Hammett treatment of the rate data indicated that the DMA solvolysis of the unsubstituted brosylate (1c) falls into the category of ks pathway (100%). In order to gain further information of the nature of the ks pathway, the DMA solvolysis of 1c or 1c-2-d (labeled at C(2)) has been conducted. The product distribution, effect of water content on it, the composition and deuterium distribution of recovered brosylate, kinetic isotope effect, and the deuterium distribution of product have been investigated. The products consisted of the olefins ((E)- and (Z)-2-pheny1-2-butenes, and 2- and 3-phenyl-1-butenes), and, in the presence of water in DMA, the carboxylates (erythro- and thero-1-methyl-2-phenylpropyl acetates) and the small amount of diastereomeric alcohols. The major product was (Z)-2-phenyl-2-butene, indicating the occurrence of anti-E1 process. The deuterium was substantially scrambled in each product. These findings suggest that the reaction proceeds through tight ion-pair and subsequent processes such as anti-E1, 2,1-phenyl and -hydride shifts, solvent capture, and threo-erythro interconversion take place competitively. In view of a substantial extent of intervention of such rearrangement, the involvement of nucleophilic solvent assistance is thought to be less probable in this ks process.

Structural effects in solvolytic reactions. 26. A critical study of the effect of solvent on the exo:endo rate ratio in the solvolysis of 2-norbornyl derivatives. Evidence that the exo:endo rate ratio is not the result of K.DELTA./Ks processes

The generally accepted position that the exo:endo rate ratio in the solvolysis of 2-norbornyl derivatives is the result of a k/sub ..delta../ process for exo and a k/sub s/ process for endo was subjected to critical examination by investigating the exo:endo rate ratio as a function of solvent. These mesylates were synthesized, along with several representative derivatives (isopropyl, cyclopentyl, and cyclohexyl), and solvolyzed in pure water and in 60 percent aqueous acetone. The tosylates were solvolyzed in methanol and in formic acid. These data, as well as other data, including those for solvolysis in trifluoroacetic acid and hexafluoroisopropyl alcohol, were then subjected to critical examination. Over the entire range of solvents, log k/sub exo/ plots linearly against log k/sub endo/. This is not consistent with the usual interpretation that the solvolysis of the exo isomer involves a k/sub ..delta../ process, insensitive to the nucleophilicity of the solvent, whereas the solvolysis of the endo isomer involves a k/sub s/ process, sensitive to the nucleophilicity of the solvent. The solvolysis of 2-adamantyl tosylate has been proposed as a representative k/sub c/ process. Both exo- and endo-norbornyl tosylates are nicely correlated with the rates of solvolysis of 2-adamantyl tosylates over the exceptionally widemore » range of solvents here examined. On the other hand, isopropyl, cyclopentyl, and cyclohexyl derivatives, postulated to involve k/sub s/ processes, are not so correlated. Clearly it is necessary to reconsider the previous interpretation of the solvolysis of endo-norbornyl derivatives as involving a k/sub s/ process and the exo:endo rate ratio as arising from the operation of k/sub ..delta..//k/sub s/ processes. The data are in better agreement with the solvolyses of both exo- and endo-norbornyl proceeding through processes that are essentially k/sub c/.« less

Parallelism in Artificial Intelligence Problem Solving: A Case Study of Hearsay II

The Hearsay II speech-understanding system (HSII) (Lesser et al [11], Fennell [9], and Erman and Lesser [6]) is an implementation of a knowledge-based multiprocessing artificial intelligence (AI) problem-solving organization. HSII is intended to represent a problem-solving organization which is applicable for implementation in a parallel hardware environment such as C.mmp (Bell et al [2]). The primary characteristics of this organization include: 1) multiple, diverse, independent and asynchronously executing knowledge sources (KS's), 2) cooperating (in terms of control) via a generalized form of the hypothesize-and-test paradigm involving the data-directed invocation of KS processes, and 3) communicating (in terms of data) via a shared blackboard-like data base in which the current data state is held in a homogeneous, multidimensional, directed-graph structure. The object of this paper is to explore several of the ramifications of such a problem-solving organization by examining the mechanisms and policies underlying HSII which are necessary for supporting its organization as a multiprocessing system. In addition, a multiprocessor simulation study is presented which details the effects of actually implementing such a parallel organization for use in a particular application area, that of speech understanding.

Effects of sodium azide on the solvolysis of secondary and primary .beta.-arylpropyl derivatives. Azide ion as a probe for ks processes

Effects of sodium azide on the solvolysis of secondary and primary .beta.-arylpropyl derivatives. Azide ion as a probe for ks processes