Dispersion Ratio Research Articles

Land use impact on clay dispersion/flocculation in irrigated and flooded vertisols from Northern Cameroon

Clay dispersion by water is important for soil and water conservation as well as for irrigation scheduling. In the present study, clay dispersion/flocculation of irrigated and flooded vertisols in North Cameroon was investigated using clay dispersion/stability indices. Nine vertisols topsoils (0–20 cm) samples were collected on different land use and their clay dispersion indices were assessed. Vertisols were acidic to slightly basic, with smectites as dominant clay mineral. The water dispersible clay (160–340 g kg−1), the dispersion ratio (0.55–0.79) and the clay dispersion ratio (0.48–0.83) were high in the studied vertisols while the clay flocculation index (0.17–0.54) and the clay aggregation (70–230 g kg−1) were low to moderate, indicating their high dispersion. Cropped vertisols displayed the higher amount of water dispersible clay while not cropped recorded the smaller amount. Concerning the cropped soils, irrigated vertisols displayed the highest clay dispersion indices suggesting that agricultural practices (irrigation) enhance clay dispersion. Globally, the clay dispersibility trend was: irrigated paddy ˃ rainy sorghum ˃ rainfed paddy ˃ dry-season sorghum ˃ not cropped. Statistical analyses revealed that amorphous Al, Na+ and electrical conductivity enhance clay dispersion while organic matter, nitrogen and Ca++ promote clay flocculation/aggregation. The overall findings emphasized that practices such as heavy tillage and irrigation induce clay dispersion. Minimum tillage, electrolytes concentration monitoring in irrigation water, irrigation scheduling based on soil moisture control, organic matter inputs and implementation of adapted dams are measures susceptible to limit their degradation through clay dispersion.

Effects of intermode nonlinearity and intramode nonlinearity on modulation instability in randomly birefringent two-mode optical fibers

We analyze in detail the effects of the intermode nonlinearity (IEMN) and intramode nonlinearity (IRMN) on modulation instability (MI) in randomly birefringent two-mode optical fibers (RB-TMFs). In the anomalous dispersion regime, the MI gain enhances significantly as the IEMN and IRMN coefficients increases. In the normal dispersion regime, MI can be generated without the differential mode group delay (DMGD) effect, as long as the IEMN coefficient between two distinct modes is above a critical value, or the IRMN coefficient inside a mode is below a critical value. This critical IEMN (IRMN) coefficient depends strongly on the given IRMN (IEMN) coefficient and DMGD for a given nonlinear RB-TMF structure, and is independent on the input total power, the power ratio distribution and the group velocity dispersion (GVD) ratio between the two modes. On the other hand, in contrast to the MI band arising from the pure effect of DMGD in the normal dispersion regime, where MI vanishes after a critical total power, the generated MI band under the combined effects of IEMN and IRMN without DMGD exists for any total power and enhances with the total power. The MI analysis is verified numerically by launching perturbed continuous waves (CWs) with wave propagation method.

Female dispersion and sex ratios interact in the evolution of mating behavior: a computational model

The evolution of mating strategies is not well understood. Several hypotheses have been proposed to explain the variation in mating strategies, with varying levels of support. Specifically, female dispersion, adult sex ratio and mate guarding have been proposed as drivers of the evolution of monogamous strategies. In this study, we used an agent-based model (ABM) to examine how different mating behaviors evolve in a population under different conditions related to these putative drivers, looking to understand the interaction between them. We found an interaction among different factors in the evolution of social monogamy, and their impact is in this order: adult sex ratio (ASR), female dispersion and extra-pair copulation. Thus, when the adult sex ratio is male-biased, monogamous strategies are strongly favored. However, this is only the case if mate guarding is fully efficient, i.e., if there is no extra-pair copulation. On the other hand, in scenarios where the population is female-biased, or mate guarding is not efficient, we find that polygamous strategies are favored but proportionally to the dispersion of females. These results confirm previous findings regarding mate guarding and sex ratios, while also showing how female dispersion enters the dynamics.

NİĞDE AKKAYA BARAJI HAVZASINDA ARAZİ KULLANIMI/ARAZİ ÖRTÜSÜ DEĞİŞİMİNİN BAZI TOPRAK ÖZELLİKLERİ ÜZERİNE ETKİLERİ

Bu çalışma arazi kullanımı/arazi örtüsündeki (ürün deseni) farklılaşmanın toprakların bazı hidro-fiziksel ve kimyasal özellikleri üzerindeki etkilerini belirlemek amacıyla yapılmıştır. Çalışma alanı olarak Niğde-Akkaya Barajı havzası içerisindeki araziler seçilmiştir. Araştırma amacına ulaşmak için, ekolojik koşulları benzer olan ve çeşitli ürünlerin (fasulye, patates, yonca, elma) yetiştirildiği tarım alanı, 2 yıldır nadasa bırakılmış tarım alanı ve mera alanından toprak örnekleri alınmıştır. Örnekler her bir arazi kullanımı/arazi örtüsünün olduğu arazilerden alanı temsil ettiği düşünülen 20 m x 20 m’lik 2 örnekleme alanından 3’er noktadan usulüne uygun şekilde 0-20 cm derinlikten doğal yapısı bozulmuş ve doğal yapısı bozulmamış olarak alınmıştır. Toprak örneklerinin tane boyut dağılımı (Tekstür), tane yoğunluğu, pH, elektriksel iletkenlik, organik madde, dispersiyon oranı, hacim ağırlığı, porozite, maksimum su tutma kapasitesi, hidrolik geçirgenlik (permeabilite) özellikleri belirlenmiştir. Araştırma sonuçlarına göre genel olarak araştırma alanı toprakları erozyona duyarlıdır. Genel olarak araştırma alanlarından alınan örnekler üzerinde yapılan analiz sonuçlarında arazi kullanımı/arazi örtüsü değişimlerinden hacim ağırlığı, porozite, pH, organik madde, permeabilite, kil, kum, silt, dispersiyon oranı özellikleri etkilenmektedir.

Wormlike Acid-Doped Polyaniline: Controllable Electrical Properties and Theoretical Investigation

Polyaniline doped with hydrochloride acid was prepared via a chemical oxidative polymerization between APS oxidant and aniline monomer in hydrochloric acid solution with different concentrations. The diameter of each PANI wormlike nanorod is fairly uniform, and the diameter of PANI nanorod decreases with increase in concentration of HCl. For the degradation stage of the polymeric backbone, the rate of degradation increases with decrease in the HCl concentration, which means the samples synthesized in higher HCl concentration possess the more stable structures. The highest conductivity of 1.04 S/cm is achieved when HCl concentration is 1.0 mol/L, which generated uniformly branched knobbles with good dispersion and higher aspect ratio. The variation tendency of complex permittivity keeps coordinate with the conductivity. First-principles calculations verified that N(E) of PANIs in the protonated states are larger than that of the unprotonated PANI, which means that the conductivity is promoted by the intera...

Elastic preserving projections based on L1-norm maximization

Elastic preserving projections (EPP) is a classical manifold learning technique for dimensionality reduction, which has demonstrated good performance in pattern recognition. However, EPP is sensitive to the outliers because it makes use of the L2-norm for optimization. In this paper, we propose an effective and robust EPP version based on L1-norm maxmization (EPP-L1), which can learn the optimal projection vectors by maximizing the ratio of the global dispersion to the local dispersion using the L1-norm rather than L2-norm. The proposed method is proved to be feasible and also robust to outliers while overcoming the singular problem of the local scatter matrix for EPP. Experiments on five popular face image databases demonstrate the effectiveness of the proposed method.

Revisiting the stellar velocity ellipsoid–Hubble-type relation: observations versus simulations

The stellar velocity ellipsoid (SVE) in galaxies can provide important information on the processes that participate in the dynamical heating of their disc components (e.g. giant molecular clouds, mergers, spiral density waves, bars). Earlier findings suggested a strong relation between the shape of the disc SVE and Hubble type, with later-type galaxies displaying more anisotropic ellipsoids and early-types being more isotropic. In this paper, we revisit the strength of this relation using an exhaustive compilation of observational results from the literature on this issue. We find no clear correlation between the shape of the disc SVE and morphological type, and show that galaxies with the same Hubble type display a wide range of vertical-to-radial velocity dispersion ratios. The points are distributed around a mean value and scatter of $\sigma_z/\sigma_R=0.7\pm 0.2$. With the aid of numerical simulations, we argue that different mechanisms might influence the shape of the SVE in the same manner and that the same process (e.g. mergers) does not have the same impact in all the galaxies. The complexity of the observational picture is confirmed by these simulations, which suggest that the vertical-to-radial axis ratio of the SVE is not a good indicator of the main source of disc heating. Our analysis of those simulations also indicates that the observed shape of the disc SVE may be affected by several processes simultaneously and that the signatures of some of them (e.g. mergers) fade over time.

Laboratory Scale Investigation of Dispersion Effects on Saltwater Movement due to Cutoff Wall Installation

In the numerical investigation of saltwater transport in coastal aquifers, we need to correctly evaluate the hydrodynamic dispersion in the flow field. In this study, we focused on the role of dispersivity in the removal process of residual saltwater in a laboratory scale cutoff wall experiment. From a pulse-type fluorescent tracer injection experiment in a saturated porous media of glass beads with a mean diameter of 0.088 cm, the estimated longitudinal and transverse dispersivities were found to be 0.07 cm and 0.0025 cm, respectively. Numerical analysis of the saltwater intrusion and subsequent removal after cutoff wall installation using SEAWAT and the generated dispersivity ratio (αL/αT) of 28 reproduces well the measured salt concentration changes with time. Whereas, if a dispersivity ratio of 10 is used in the numerical simulation, transverse dispersion in the saltwater and freshwater mixing zone becomes large and the residual saltwater is removed faster than the laboratory experiment. Inversely, if 100 was used, the residual saltwater removal time took longer. The transverse dispersion is a key parameter in the mechanical dispersion of saltwater in the mixing zone after cutoff wall installation.

The use of the empirical mode decomposition method to clean and restavration acoustic emission signal

The results of the study of the possibility of using the empirical mode decomposition method for cleaning geoacoustic emission signals from various types of noise are presented. It is shown that the application of the method allows to increase the ratio of the signal noise 3-6 dB depending on the ratio of signal dispersion and noise in the input signal. The examples demonstrate the ability to remove trends and harmonic interference, as well as the ability to highlight a useful signal when masking its powerful noise. A comparative evaluation of the method in relation to the low-frequency filtration is carried out. The limitation of the method applicability in the case of processing of pulse signals asymmetric with respect to its average value is indicated.

An Active Feature Selection Strategy for DWT in Artificial Taste

A discrete wavelet transform (DWT) extracts meaningful information in a time-frequency domain and is a favorable feature extraction approach from pulse-like responses in large pulse voltammetry (LAPV) electronic tongues (e-tongue). A regular DWT generates lots of coefficients to describe signal details and approximations at different scales. Thus, coefficient selection is necessary to reduce the feature size. However, the common DWT-based feature selection follows a passive mode: manipulation through human experience or exhaustive trials. It is subjective, time consuming, and barely works in nonlaboratory conditions. In this paper, we present an active feature selection strategy consisting of a dispersion ratio computation and optimal searching search. To evaluate the performance of the proposed method, we prepared several beverage samples and performed experiments with a LAPV e-tongue. Meanwhile, the features of raw response, peak-inflection point, referenced DWT method, and our proposed method were presented to indicate the effects of the refined features of the proposed method. Furthermore, we utilized several classifiers such as the k-nearest neighbor (k-NN), support vector machine (SVM), and random forest (RF) to evaluate the improvement of recognition by the refined features. Compared with other regular feature extraction methods, the proposed method can automatically explore high-quality features with an acceptable feature size. Moreover, the highest average accuracy was achieved by the proposed method for each classifier. It is an alternative feature extraction approach for a LAPV e-tongue without any manipulation in real applications.

Matrix solid-phase dispersion method coupled with high-performance liquid chromatography for the simultaneous quantification of selected compounds from freeze dry pomegranate juice

In this research, a novel method was developed for the matrix solid phase dispersion (MSPD) followed by high-performance liquid chromatography (HPLC) quantification of four marker constituents (vitamin C, gallic acid, rutin, and ellagic acid) in the freeze-dried pomegranate fruit juice. Various MSPD parameters like type of dispersant, sample–dispersant ratio, solvents, its volume, and time of extraction have been optimized after many trials. Furthermore, HPLC method has been developed and optimized for the analysis of all four components. The HPLC separation was achieved using a 250 × 4.6 mm column, particle size of 5 μm, C18 reverse phase column, with a mobile phase consisting of acetonitrile and 0.05% H3PO4, in gradient elution mode with a mobile phase flow rate of 1 mL/min, using ultraviolet (UV)–visible detection at 254 nm. All calibration curves showed good linear regression (r2 ≥ 0.9925) within test ranges. The extraction recoveries of the marker constituents analyzed by MSPD methods were found as ranging from 97.5% to 103.5%. From comparing the chromatograms, validation data and other parameters like time, labor, and feasibility, we found that MSPD technique was most suitable for the analysis as compared to conventional liquid–liquid extraction technique.

Influence of natural regeneration on fractal features of residue microaggregates in bauxite residue disposal areas

AbstractBauxite residue is often physically degraded, which limits vegetation establishment on the disposal areas. Microaggregate stability is an important physical property due to its significant effect on erosion and surface runoff; however, this is rarely reported for bauxite residue. Native plant encroachment on a bauxite residue disposal area in Central China has revealed that natural regeneration may ameliorate the residue and help to support plant growth. Residue samples from 5 different disposal ages were collected to determine microaggregate stability and to identify their fractal features. Following natural regeneration, the aggregate fraction 250–50 μm increased significantly from 27.4% to 40.3%, whilst the silt + clay size aggregate fraction decreased from 58.4% to 30.7%. With increasing disposal age, the residue clay dispersion ratio (CDR) ranged from 7.7% to 22.5%, whilst aggregated silt and clay ranged from 15.3% to 19.0%, indicating a stable microaggregate structure. The single‐fractal dimension (D) of the residues for different disposal ages varied from 2.2 to 2.4. The high pH and salinity of bauxite residue indicated a high value of single‐fractal dimension. The multifractal parameters of residue microaggregates, including capacity dimension (D0), information dimension (D1), and information dimension/capacity dimension (D1/D0), decreased, which resulted in homogeneity following natural regeneration. Correlation analysis revealed that both single‐fractal and multifractal dimensions had significant correlations with residue microaggregate stability. Our results suggested that natural regeneration may improve microaggregate stability of bauxite residue, and fractal parameters of residue microaggregates may be used to describe residue microaggregate stability and the physical condition of bauxite residue.

Necessary and sufficient conditions for stochastic orders between (n − r + 1)-out-of-n systems in proportional hazard (reversed hazard) rates model

ABSTRACTConsider two (n − r + 1)-out-of-n systems, one with independent and non-identically distributed components and another with independent and identically distributed components. When the lifetimes of components follow the proportional hazard rates model, we establish a necessary and sufficient condition for the usual stochastic order to hold between the lifetimes of these two systems. For the special case of r = 2, some generalized forms of this result to the hazard rate, dispersive and likelihood ratio orders are also obtained. Moreover, for the case when the lifetimes of components follow the proportional reversed hazard rates model, we derive some similar results for comparing the lifetimes of two systems . Applications of the established results to different situations are finally illustrated.

AISI 304 Steel Brazing Using A Flexible Brazing Foil Fabricated by Tape Casting Method

The authors report the fabrication of a flexible nickel brazing foil using powdered nickel alloy filler (BNi-2) mixed with an organic binder. The organic binder was composed of a polyacrylic acid polymer, glycol, carbon tetrachloride, and water as a dispersion medium for the powder. The brazing paste so formed was then tape-cast on a polymer foil with different polymer to paste (dispersant) ratios, of □ 9:1, 8:2 and 7:3 by weight, and was dried in a low-temperature oven. The filler pyrolysis temperature, paste spreading, permeability, and wettability were examined. The thermal analysis results showed that the filler paste decomposition temperature was in the range of 463-498 ℃, while the tape-cast brazing foil had a pyrolysis temperature of □334.36 ℃. The resulting flexible self-adhesive foil was used to braze steel foils. The AISI 304 steel joint microstructure and joint tensile shear tests were also performed. It was found that the brazing foil produced □1 wt% of residue after melting. The microstructural analysis showed a uniform distribution of a Cr-rich in Ni-rich matrix at a polymer to dispersant ratio of 8:2. It is suggested that the wettability of the brazing foil on AISI 304 steel will be maximum, and a higher joint strength can be obtained when the polymer to dispersant ratio is kept at 8:2. (Received May 29. 2017; Accepted September 14, 2017)

Stepwise joint inversion of surface wave dispersion, Rayleigh wave ZH ratio, and receiver function data for 1D crustal shear wave velocity structure

Accurate determination of seismic velocity of the crust is important for understanding regional tectonics and crustal evolution of the Earth. We propose a stepwise joint linearized inversion method using surface wave dispersion, Rayleigh wave ZH ratio (i.e., ellipticity), and receiver function data to better resolve 1D crustal shear wave velocity (vS) structure. Surface wave dispersion and Rayleigh wave ZH ratio data are more sensitive to absolute variations of shear wave speed at depths, but their sensitivity kernels to shear wave speeds are different and complimentary. However, receiver function data are more sensitive to sharp velocity contrast (e.g., due to the existence of crustal interfaces) and vP/vS ratios. The stepwise inversion method takes advantages of the complementary sensitivities of each dataset to better constrain the vS model in the crust. We firstly invert surface wave dispersion and ZH ratio data to obtain a 1D smooth absolute vS model and then incorporate receiver function data in the joint inversion to obtain a finer vS model with better constraints on interface structures. Through synthetic tests, Monte Carlo error analyses, and application to real data, we demonstrate that the proposed joint inversion method can resolve robust crustal vS structures and with little initial model dependency.

The KMOS Redshift One Spectroscopic Survey (KROSS): the origin of disc turbulence in z ≈ 1 star-forming galaxies

We analyse the velocity dispersion properties of 472 z~0.9 star-forming galaxies observed as part of the KMOS Redshift One Spectroscopic Survey (KROSS). The majority of this sample is rotationally dominated (83 +/- 5% with v_C/sigma_0 > 1) but also dynamically hot and highly turbulent. After correcting for beam smearing effects, the median intrinsic velocity dispersion for the final sample is sigma_0 = 43.2 +/- 0.8 km/s with a rotational velocity to dispersion ratio of v_C/sigma_0 = 2.6 +/- 0.1. To explore the relationship between velocity dispersion, stellar mass, star formation rate and redshift we combine KROSS with data from the SAMI survey (z~0.05) and an intermediate redshift MUSE sample (z~0.5). While there is, at most, a weak trend between velocity dispersion and stellar mass, at fixed mass there is a strong increase with redshift. At all redshifts, galaxies appear to follow the same weak trend of increasing velocity dispersion with star formation rate. Our results are consistent with an evolution of galaxy dynamics driven by disks that are more gas rich, and increasingly gravitationally unstable, as a function of increasing redshift. Finally, we test two analytic models that predict turbulence is driven by either gravitational instabilities or stellar feedback. Both provide an adequate description of the data, and further observations are required to rule out either model.

Improved dispersion of graphite derivatives by solution plasma

Solution plasma is applied to graphite and thermally reduced graphite oxide in ambient conditions in order to improve their dispersion. Changes in morphology, oxygen functional groups, defects, decomposition temperatures, oxygen to carbon atomic ratio, conductivity, stability, and degree of dispersion are systematically investigated by using scanning electron microscopy, Fourier-transform infrared spectroscopy, Raman spectroscopy, Thermogravimetric analysis, X-ray photoelectron spectroscopy, Zeta potential analyzers, and ultraviolet–visible spectrophotometry. Dramatic enhancement of the dispersion after the simple plasma treatment is introduced without evident change of conductivities. This simple, easy, economical, and eco-friendly plasma method could functionalize and reform material efficiently in many application fields.

Extraction of acetanilides in rice using ionic liquid-based matrix solid phase dispersion-solvent flotation

Ionic liquid-based matrix solid phase dispersion-solvent flotation coupled with high performance liquid chromatography was developed for the determination of the acetanilide herbicides, including metazachlor, propanil, alachlor, propisochlor, pretilachlor, and butachlor in rice samples. Some experimental parameters, including the type of dispersant, the mass ratio of dispersant to sample, pH of sample solution, the type of extraction solvent, the type of ionic liquid, flotation time, and flow rate of N2 were optimized. The average recoveries of the acetanilide herbicides at spiked concentrations of 50, 125, and 250 µg/kg ranged from 89.4% to 108.7%, and relative standard deviations were equal to or lower than 7.1%, the limits of quantification were in the range of 38.0 to 84.7 µg/kg.

Evaluation of impacts of cooling tower design properties on the near-field environment

In a nuclear power plant, ultimate heat sink (UHS) and circulating water system (CWS) cooling towers both ultimately remove heat from the essential service water system, main condenser, and non-essential service water system during all operation modes including accident conditions. Since the visible plume from the cooling tower has an adverse effect on the environment, however, an environmental impact assessment of the cooling tower is required for the construction of a new nuclear power plant. In this study, the environmental impact of UHS and CWS cooling towers of an APR1400 standard design plant was assessed for the purpose of testing and demonstrating the recently-updated SACTI2 model. Because the site for the APR1400 standard design plant had not been decided, one-year meteorological data from the Spokane International Airport weather station, WA, USA, were used as hypothetical input data for the environmental impact assessment. The quantitative effect of cooling tower design changes on the environment was analyzed in terms of index-value dispersion area (AD) and dispersion ratio (δ) for nine environmental assessment indexes. Scenario test conditions were varied by changing cooling tower arrangement, distance between cooling towers, length of cooling tower, exit port height, exit port diameter, the number of exit ports, heat load per tower, and air flow rate per tower.

Gemini NIFS survey of feeding and feedback processes in nearby active galaxies – II. The sample and surface mass density profiles

We present and characterize a sample of 20 nearby Seyfert galaxies selected for having BAT 14--195keV luminosities $L_X \ge 10^{41.5}$ erg s$^{-1}$, redshift $z\le$0.015, being accessible for observations with the Gemini Near-Infrared Field Spectrograph (NIFS) and showing extended [OIII]$\lambda$5007 emission. Our goal is to study Active Galactic Nuclei (AGN) feeding and feedback processes from near-infrared integral-field spectra, that include both ionized (HII) and hot molecular (H$_2$) emission. This sample is complemented by other 9 Seyfert galaxies previously observed with NIFS. We show that the host galaxy properties (absolute magnitudes $M_B$, $M_H$, central stellar velocity dispersion and axial ratio) show a similar distribution to those of the 69 BAT AGN. For the 20 galaxies already observed, we present surface mass density ($\Sigma$) profiles for HII and H$_2$ in their inner $\sim$500 pc, showing that HII emission presents a steeper radial gradient than H$_2$. This can be attributed to the different excitation mechanisms: ionization by AGN radiation for HII and heating by X-rays for H$_2$. The mean surface mass densities are in the range ($0.2\le \Sigma_{HII} \le 35.9$)M$_\odot$pc$^{-2}$, and ($0.2\le \Sigma_{H2} \le 13.9$)$\times10^{-3}$M$_\odot$pc$^{-2}$, while the ratios between the HII and H$_2$ masses range between $\sim$200 to 8000. The sample presented here will be used in future papers to map AGN gas excitation and kinematics, providing a census of the mass inflow and outflow rates and power as well as their relation with the AGN luminosity.