Search

Silicon nitride (Si 3 N 4) ceramics, with different ratios of fine and coarse α-Si 3 N 4 powders, were prepared by spark plasma sintering (SPS) and heat treatment. Further, the influence of coarse α-Si 3 N 4 powder on densification, microstructure, mechanical properties, and thermal behavior of Si 3 N 4 ceramics was systematically investigated. Compared with fine particles, coarse particles exhibit a slower phase transition rate and remain intact until the end of SPS. The remaining large-sized grains of coarse α-Si 3 N 4 induce extensive growth of neighboring β-Si 3 N 4 grains and promote the development of large elongated grains. Noteworthy, an appropriate number of large elongated grains distributed among fine-grained matrix forms bimodal microstructural distribution, which is conducive to superior flexural strength. Herein, Si 3 N 4 ceramics with flexural strength of 861.34 MPa and thermal conductivity of 65.76 W m−1 K−1 were obtained after the addition of 40 wt% coarse α-Si 3 N 4 powder. [ABSTRACT FROM AUTHOR]

The effects of body force/external pressure gradient on the statistical behaviours of the reaction progress variable variance and the terms of its transport equation have been investigated for different turbulence intensities using DNS data of statistically planar flames. Since the extent of flame wrinkling increases with the strengthening of body force promoting unstable stratification, the scalar variance has been found to decrease under strong body force promoting stability. This trend is particularly strong for low turbulence intensities where the probability density function of the reaction progress variable cannot be approximated by a bimodal distribution. Therefore, an algebraic relation for the reaction progress variable variance, derived based on a presumed bimodal probability density function of reaction progress variable, cannot be used for general flow conditions. The contributions of chemical reaction and scalar dissipation rates in the scalar variance transport equation remain leading order source and sink, respectively for all cases irrespective of the strength and direction of the body force. The counter-gradient type transport is found to weaken with increasing body force magnitude when the body force is directed from the heavier unburned gas to the lighter burned gas side of the flame brush, and vice versa. Although a scalar dissipation rate-based reaction rate closure can be utilised to model the reaction rate contribution to the scalar variance transport accurately, the dissipation rate contribution due to the gradient of the Favre-averaged reaction progress variable cannot be ignored and it plays a key role for large magnitudes of body force promoting stable stratification. An algebraic closure of the scalar dissipation rate, originally proposed for high Damköhler number combustion, has been modified for the thin reaction zones regime combustion by incorporating the effects of Froude number. This model has been shown to predict the scalar dissipation rate accurately for all cases considered here. [ABSTRACT FROM AUTHOR]

Quantitative analysis of error sources in wave measurement intercomparison under real-world conditions remains challenging due to various factors such as spatial and temporal offsets in the field, diverse configurations of wave sensors and platforms, and distinct measurement algorithms. This study introduces a modified error analysis method based on sampling variability. Measurements from two co-deployed Datawell Waverider buoys at the National Marine Test Site (Weihai) in China offer an opportunity to assess the spatial variability error. The results reveal that for non-directional wave parameters, like significant wave height and mean zero-crossing period, the wave conditions in the field can be considered stationary, with random errors primarily arising from inherent sampling variability. Spatial offsets significantly impact directional wave parameters at peak frequencies, with large deviations (greater than 20°) in peak wave direction primarily attributed to bimodal distribution. For data with significant wave heights exceeding 0.5 m, random errors in the mean wave direction at the same frequency can be mainly attributed to sampling variability. The bulk directional wave parameters weighted by the energy spectrum demonstrate lower sensitivity to spatial offsets, and there is excellent agreement between the bulk mean directions when considering only the unimodal distribution data. • Wave intercomparison of two co-deployed Datawell Waverider buoys was analyzed. • Random error of non-directional parameters mainly arises from sampling variability. • The directional wave parameters at peak frequencies are sensitive to spatial offsets. • Excellent agreement between the bulk mean direction of unimodal distribution data. [ABSTRACT FROM AUTHOR]

Statistical analyses of the first pop-in stress data, obtained by spherical tip-nanoindentation experiments on different metallic glasses (MGs) with tip radius, R i , loading rate, P ˙ , and structural state of the glass as experimental variables, show that the 3-parameter bimodal Weibull distribution best captures the stochastic nature of the incipient plastic strengths. Significant bimodality in the strength distributions was observed only when a larger R i and P ˙ are employed. We hypothesize that the stress required for shear band nucleation has to exceed a critical value over a characteristic distance over which the stress gradients are minimum to rationalize the bimodality. Image, graphical abstract [ABSTRACT FROM AUTHOR]

• Formations of heart-shaped film and fountain are attributed to two films merging. • Evolution of fountain and size characteristics of splashes are revealed. • Splashes volume concentration shows a bimodal distribution after fountain breakup. The technology of liquid film by jet impingement is widely applied in aerospace, electronics and cleaning. In this paper, the spreading and evolution of the liquid films formed by two continuous jets impinging obliquely on a vertical wall are experimentally studied. The effects of the jet Weber number, jet inclination angle, nozzles spacing and angle between two jets on the films are examined. Results show that three flow patterns are observed as the experimental conditions vary, including two separated liquid films, a heart-shaped liquid film and a heart-shaped film with the fountain sheet breakup. The formation of a heart-shaped liquid film is attributed to the merging of two films and results in the spreading area and length of the film increasing suddenly. The fountain sheet forms when two liquid films merge, and develops with the increase of the jet Weber number. When the balance between the surface tension on the fountain sheet and the inertial force as well as gravity that form the fountain is disrupted, the fountain sheet breaks up, and causes the splashing rate to increase suddenly. The volume concentration of the splashing droplet size displays the bimodal distribution after the occurrence of the fountain sheet breakup, which indicates the existence of two splashing droplet formation mechanisms in the systems, the surface wave and fountain sheet breakup. The height variation of the left and right peaks of the bimodal distribution reflects the competition between the two splashing generation mechanisms. [ABSTRACT FROM AUTHOR]

To reveal the inhibitory effect of stoichiometric methane/air explosions, NaHCO 3 with a bimodal distribution were selected as inhibitors. A 5 L vertical transparent duct was used. All the results revealed that Blend 82 , whose mass fraction contained 80% OP 500 – 600 and 20% OP 200 – 220 NaHCO 3 , exhibited the optimal inhibitory effect. For the bimodal distribution of NaHCO 3 , assessing the inhibitory effect solely on the basis of a single particle size parameter is unreliable. Synergistic effects between particles of different sizes should be considered when the interaction index I S < 1. Multiple size classes of bimodal NaHCO 3 were proposed for use in response surface methodology to predict the inhibitory effect of methane/air flames. Furthermore, we employed a detailed chemical kinetic model to quantify the endothermic and chemical effects of NaHCO 3 on the laminar burning velocity of methane/air flames and established a good relationship between the explosion parameters and laminar flame properties. [Display omitted] • An optimal mass ratio exists between OP 500 – 600 and OP 200 – 220 in NaHCO 3 blends. • Synergistic effects between two inhibitors with different sizes are quantified. • Drop ratios in overpressure can be predicted via response surface methodology. • The endothermic effect of NaHCO 3 is considered in the kinetic calculations. • A correlation between explosion parameters and laminar flame properties is found. [ABSTRACT FROM AUTHOR]

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal). This article has been retracted at the request of the authors as it contains erroneous experimental results, pictures, discussions and conclusions related to IL-1β and TNF-α. The authors were unable to repeat the experimental results of IL-1β and TNF-α in the subsequent 2 repeated experiments. We apologise and inform the readers of the journal that the conclusions of the manuscript are invalid. [ABSTRACT FROM AUTHOR]

• Coincident ACE-FTS and SAGE III/ISS data combined to study sulfate aerosols. • Investigated volcanically enhanced (Raikoke and Tonga) plus background conditions. • Bimodal size distributions gave better results than monomodal. • Assuming monomodal size distribution underestimates impact on climate. Combining infrared aerosol transmittance spectra from the Atmospheric Chemistry Experiment Fourier transform spectrometer (ACE-FTS) and visible/near infrared extinction information from coincident SAGE III/ISS measurements, the properties of stratospheric sulfate aerosols are derived under various conditions. Assuming a bimodal size log-normal distribution (rather than a monomodal one) is required to properly characterize the spectra. Analysis is performed for enhanced sulfate conditions following two recent volcanic eruptions, the Raikoke eruption in 2019 and the Hunga Tonga-Hunga Ha'apai eruption in 2022, as well as for measurements under background sulfate conditions. The traditional analysis approach of assuming a monomodal distribution likely contributes to the large uncertainties for the impact of sulfate aerosols on climate. [ABSTRACT FROM AUTHOR]

The influence of interrupted ageing on the temporal evolution of γ′ distribution in alloy 718Plus has been examined. Various bimodal γ′ distributions were generated as a function of ageing duration, and the peak-aged distribution was identified through hardness tests. The volume fractions of the large and fine γ′ precipitates evolved into a near 50:50% uniform distribution. The γ″ precipitation succeeded the γ′ precipitation during low-temperature ageing. The nucleation of the γ″ on γ′ is explained on the basis of the Al + Ti to Nb ratio approaching the critical value in the matrix during the ageing treatment. The preferential nucleation site for the co-precipitation of γ″ is explained on the basis of lattice misfits of the γ, the large and the fine γ′, and the γ″ phases. [Display omitted] • A uniform bimodal distribution of γ′ precipitates with a near 50:50% by volume fraction of large and fine γ′ was generated. • Co-precipitation of γ″ was found to be independent of the critical size of γ′ and depends only on the Al + Ti to Nb ratio. • The γ″ precipitates preferentially nucleated on the γ′ because of a lower lattice misfit in comparison to the matrix. [ABSTRACT FROM AUTHOR]

Abstract We use pattern matching of experimental and dynamically simulated backscattered Kikuchi diffraction (BKD) patterns to increase the orientation precision of electron backscatter diffraction (EBSD) measurements. In order to quantify the improvement in orientation precision, we analyze the experimental distribution of the kernel average misorientation (KAM) angles. We find that for the same raw data, i.e. the same EBSD data acquisition time budget, the pattern matching approach improves the KAM resolution by an order of magnitude compared to orientation data delivered from the conventional Hough-transform based data analysis. This quantitative improvement enables us to interpret small orientation changes in plastically deformed materials which are hidden in noisy orientation data delivered from the reference EBSD system. As an application example, we analyze a ferritic-martensitic steel (P92) sample before and after low-cycle fatigue (LCF) loading (± 0.3 % strain) at 620 °C. Whereas the low precision of the EBSD orientation data from the manufacturer software does not allow a reliable discrimination of the gradually changing microstructure, we find very clear systematic differences of the local microstructure after the pattern matching orientation refinement of the initial, raw pattern data. For the investigated P92 sample, the KAM-angle histograms are well described by two log-normal distributions indicating the already tempered and the remaining and mostly untempered martensite. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Pacific bluefin tuna ( Thunnus orientalis ) has two spawning grounds, and each is used at different times: May–June in the Nansei Islands of western North Pacific Ocean and July–August in the Sea of Japan. Although previous studies developed body-length based methods to differentiate between individuals originating in each spawning ground, these methods are only applicable to the young-of-the-year (YOY). In this study, we evaluate a simple technique for discerning the natal grounds of Pacific bluefin tuna greater than one year in age by observing the first annulus on the vertebrae of fish caught around Japan. We found a significant linear relationship between fork length and vertebral radius, and determined that the first annulus forms in boreal winter. Both the back-calculated fork length at the time of first annulus formation and the measured fork length of YOY in February and March had a bimodal frequency distribution, and the peaks of the two frequency distributions had similar means. The larger fork length individuals appear to have originated near the Nansei Islands, whereas the smaller fork length individuals appear to have originated in the Sea of Japan. This is because PBF hatched around the Nansei Islands will have longer growth time for the YOY to develop the first annulus at longer distance from the vertebrae center. Similarly, we observed bimodal distributions for the vertebral first annulus radius of mature Pacific bluefin tuna (>120 cm) in both spawning grounds. Our technique offers improved sample treatment efficiency and lower costs. In addition, this method may help reveal the contribution rate of each spawning ground. [ABSTRACT FROM AUTHOR]

On the basis of small-particle waterborne polyurethane(WPU-S) and large-particle waterborne polyurethane(WPU-L) which were both narrow in particle size distribution, high solid content waterborne polyurethane(WPU-H) with particle bimodal distribution was prepared by the special physical blending method. Three kinds of waterborne polyurethane were characterized by FTIR, DSC and TEM and the particle size, viscosity and solid content of the emulsion samples were measured and compared. The result showed that the WPU-H contained two kinds of particles from WPU-L and WPU-S and showed a higher solid content than WPU-L or WPU-S. Different combinations led to different high solid content, especially WPU-H-4 reached a high solid content of 66.07% and a low viscosity of 285 mPa.s by mixing WPU-L-1 and WPU-S-4. [ABSTRACT FROM AUTHOR]

Several acoustic models, such as the poro-elastic model, visco-elastic model, and multiple scattering model, have been used for describing the dispersion relation in a porous granular medium. However, these models are based on continuum or scattering theory, and therefore cannot explain the broadband measurements in cases where scattering and non-scattering losses co-exist. Additionally, since the models assume that the porous granular medium consists of grains of identical size (unimodal size distribution), the models does not account for the behavior of wave dispersion in a medium that has a distribution of differing grain sizes. As an alternative approach, this study proposes a new broadband attenuation model that describes the high frequency dispersion relation for the p-wave in the case of elastic grain scatterers existing in the background fluid medium. The broadband model combines the Biot-Stoll plus grain contact squirt and shear flow (BICSQS) model and the quasicrystalline approximation (QCA) multiple scattering model. Additionally, distribution of grain size effect is examined rudimentarily through consideration of bimodal grain size distribution. Through the quantitative analysis of the broadband model and measured data, it is shown that the model can explain the attenuation dependencies of frequency and grain size distribution for a water-saturated granular medium in the frequency range from 350 kHz to 1.1 MHz. This study can be applied to the high frequency acoustic SONAR modeling and design in the water-saturated environment. [ABSTRACT FROM AUTHOR]

Amorphous carbon and hydrogenated amorphous carbon layers were implanted at room temperature with Co ions to investigate the role of hydrogen on the Co distribution. Amorphous carbon (a:C) and hydrogenated amorphous carbon (a:C–H) films were prepared by mass selective ion beam deposition with a 5 kV acceleration voltage using C + and C 3 H 6 + ions, respectively. The typically 100 nm thin films were implanted with Co using a 30 kV acceleration voltage to a fluence of 4 × 10 16 cm −2 . Raman measurements showed that Co implantation in hydrogenated amorphous carbon causes increased sp 2 clustering while in amorphous carbon there is significant rehybridisation of carbon from sp 3 to sp 2 bonding. High resolution Rutherford backscattering measurements indicated that in the absence of hydrogen in the base matrix, the implantation profile assumes a unimodal distribution as predicted by simulations. However, in the presence of hydrogen the effects of collision cascade enhanced diffusion are significant in altering the implantation profile resulting in a bimodal distribution. The difference in the Co depth distribution between a:C and a:C–H films is explained by the change in thermal conductivity of the carbon matrix in the presence of hydrogen. The ability to position Co (magnetic atoms) in the surface region of diamond-like carbon films offers great advantages for applications in novel magnetic devices. [ABSTRACT FROM AUTHOR]

The commonly used grain size analysis technique which applies moments (sorting, skewness and kurtosis) is less useful in the case of sediments with bimodal size distributions. Herein we suggest a new simple method for analyzing the degree of grain size segregation in sand-sized sediment that has clear bimodal size distributions. Two main features are used to characterize the bimodal distribution: grain diameter segregation, which is the normalized difference between coarse and fine grain diameters, and the frequency segregation which is the normalized difference in frequencies between two modes. The new defined indices can be calculated from frequency plot curves and can be graphically represented on a two dimensional coordinate system showing the dynamical aspects of the size distribution. The results enable comparison between granular samples from different locations and/or times to shed new light on the dynamic processes involved in grain size segregation of sediments. We demonstrate here the use of this method to analyze bimodal distributions of aeolian granular samples mostly from aeolian megaripples. Six different aeolian cases were analyzed to highlight the method’s applicability, which is relevant to wide research themes in the Earth and environmental sciences, and can furthermore be easily adapted to analyze polymodal grain size distributions. [ABSTRACT FROM AUTHOR]

The effects of sequence distribution of two types of poly(propylene-ethylene) (PP-PE) copolymers, with propylene being the dominant component, on the associated crystallization behavior have been analyzed. The average sequence lengths of the crystallizable propylene sequences in these copolymers are different, although the ethylene content was virtually identical. In one case the chain configuration was completely random with crystallizable propylene sequences following Bernouillian statistics. In the other case, a bimodal distribution of crystallizable polypropylene sequences can be produced. The crystallization kinetics, the crystallization temperature, and the degree of crystallinity were significantly higher for the latter sample as compared to the former. When crystallizing from the melt, the longest crystallizable propylene sequences crystallized first at any supercooling, thus controlling the segmental mobility of other segments in the distribution. This is especially evident in copolymers with the bimodal segmental distribution. The distribution of crystallizable polypropylene sequences also controls the size distribution and thermal stability of the crystallites formed. The elucidation of the crystallization behavior of these copolymers is crucial in defining the application driven setting speeds of hot melt adhesives, the principal application of interest in our laboratory. [ABSTRACT FROM AUTHOR]

In high aspect ratio through silicon vias (TSV's), the trench step coverage (conformality) of liner, barrier and seed is critical for both the process integration and reliability. If the conformality of a deposition process is improved, the required thickness to be deposited on the field of the wafer can be reduced. Consequently, less material needs to be removed by CMP on the field, which reduces the manufacturing cost. In this paper, the reliability of two liner/barrier/seed options, which were successfully integrated into via-middle TSV's with a diameter of 3 μm and an aspect ratio (AR) of 17 is investigated. Both controlled ramp rates (IV ctrl ) as well as standard Time Dependent Dielectric Breakdown (TDDB) at 100 °C were employed as electrical testing methods to investigate the dielectric and barrier reliability properties of the studied systems. The first studied system consists of a non-conformal CVD O 3 TEOS oxide liner, an ALD TiN barrier and a PVD Cu seed. The second studied system employs a conformal ALD oxide liner, a thermal ALD WN barrier and an ELD NiB seed. Both studied systems show excellent reliability properties. Scalable highly conformal liners are more sensitive to local field enhancement at the high fields applied during highly accelerated tests which are far above normal operation conditions. Their performance at lower fields, however, still meets standard reliability specifications. [ABSTRACT FROM AUTHOR]

Alumina fillers having different morphologies were used for reinforcement of PMMA-based composite materials. The employed fillers had the same chemical composition but morphologically were spherical nanoparticles, whiskers and an electrospun product that was composed of micro-sized mostly spherical particles and nanofibers. The electrospun product was obtained from aluminum chloride hydroxide/PVA/water solution. All fillers were added without surface treatment and mechanical characteristics of obtained composites were determined using dynamic mechanical analysis (DMA) and nanoindentation. From the nanoindentation results, the reduced elastic modulus for the obtained specimens using 3 wt.% of electrospun product was 134% of the one obtained with the polymer alone and the hardness was improved to 157.8% compared to the polymer without any additive. DMA shows that the storage modulus at room temperature was twice that of the polymer alone. [ABSTRACT FROM AUTHOR]

The random daytime (RDT) sampling method was used for the first time in the assessment of average weekly exposure to uranium through drinking water in a large water supply zone. Data set of uranium concentrations determined in 106 RDT samples collected in three runs from the water supply zone in Wroclaw (Poland), cannot be simply described by normal or log-normal distributions. Therefore, a numerical method designed for the detection and calculation of bimodal distribution was applied. The extracted two distributions containing data from the summer season of 2011 and the winter season of 2012 ( n I = 72) and from the summer season of 2013 ( n II = 34) allowed to estimate means of U concentrations in drinking water: 0.947 μg/L and 1.23 μg/L, respectively. As the removal efficiency of uranium during applied treatment process is negligible, the effect of increase in uranium concentration can be explained by higher U concentration in the surface-infiltration water used for the production of drinking water. During the summer season of 2013, heavy rains were observed in Lower Silesia region, causing floods over the territory of the entire region. Fluctuations in uranium concentrations in surface-infiltration water can be attributed to releases of uranium from specific sources – migration from phosphate fertilizers and leaching from mineral deposits. Thus, exposure to uranium through drinking water may increase during extreme rainfall events. The average chronic weekly intakes of uranium through drinking water, estimated on the basis of central values of the extracted normal distributions, accounted for 3.2% and 4.1% of tolerable weekly intake. [ABSTRACT FROM AUTHOR]

Aerosol systems are more often spatially heterogeneous than homogeneous due to various factors such as turbulence in the atmosphere, flow field in a pipe, and varying generation rates at the source. As a general result, we demonstrate that an initially monodisperse and spatially heterogeneous aerosol system evolves into a bimodal size distribution purely by coagulation. The spatial inhomogeneity in the particle number concentration initiates differential coagulation rates which lead to a distribution with larger size modes in regions with higher concentration. When averaged over space , this would appear as a bimodal size distribution. We show this effect through a free-molecular coagulation model for a spatially heterogeneous system combined with the scaling theory of self-preserving distributions. It is found that sharper the occurrence of spatial heterogeneity, more pronounced is the bimodal effect. The study clearly demonstrates spatial heterogeneity as an additional factor for the origin of bimodality in aerosols. [ABSTRACT FROM AUTHOR]

In this paper a probabilistic economic dispatch model considering thermal units (fuel generators), photovoltaic arrays and wind energy conversion systems is proposed. Wind speed, solar radiation and power demand are recognized as random variables. Unavailability of each type of power source is also considered. The solution strategy is based on the Monte Carlo method and non-linear constrained optimization. The optimal solution involves single and multidimensional probabilities, descriptive statistics, cluster and bimodal analysis. The proposed methodology yields the probability distributions of system marginal price, thermal (fuel based), solar and wind power generation and load shedding. The proposed model and methodology are applied to a case study of the Northern Chilean electrical system. [ABSTRACT FROM AUTHOR]

[Display omitted] • Amp-Melt-Amp apparent dihedral angle distribution shows bimodality. • Bimodality becomes obvious after annealing for more than 1 h at 0.6 GPa and 970 °C. • Median-standard deviation evolution obeys no longer a unidirectional change. • The high anisotropy of amphibole is the main cause of the bimodality. The dihedral angle of mineral-melt is a very important parameter for further understanding the textural evolution of magma crystallization. In this study, we have investigated the amphibole-melt dihedral angle distribution of four previous experimental samples at 0.6 GPa and 970 °C with annealing time of 1 h, 10 h, 60 h, and 100 h, as well as two additional experiments with annealing time of 5 h and 30 h. In this experiment, we have achieved the assemblage of amphibole + granodioritic melt ± traces of other minerals in the process of melt crystallization under the above experimental conditions. The apparent dihedral angles of amphibole-melt of the experimental products were obtained by randomly measuring the dihedral angles in the backscattered images. The results indicate that the apparent dihedral angle presents a gradually obvious bimodal distribution with the increasing annealing time. The high anisotropy of amphibole is believed to be the main cause of the bimodal characteristics of the apparent dihedral angle distribution. Consequently, two Gauss functions are used to fit one distribution. As the annealing time increases, the median-standard deviation relationships of the apparent dihedral angle for these two Gauss functions show great differences. Therefore, our experiments proved that in the amphibole-melt system, the median-standard deviation with the growth of textural equilibrium in the early crystallization is no longer a unidirectional change. Furthermore, combining the results of this study and the previous work, whether the dihedral angle distribution in the early crystallization is unimodal or bimodal may have great relationship with the anisotropy of minerals. [ABSTRACT FROM AUTHOR]

In this study, the physical properties of refractory BC (rBC) including mass concentration, core size distribution and mixing state were in-situ characterized with a single particle soot photometer (SP2) at a polluted rural site in the North China Plain in November 2018. The average rBC mass concentration is 4.12 ± 2.47 μg m−3, accounting for 6.26% of PM 1 mass. Its diurnal variation shows that the rBC concentration is affected by both the local residential activities and the evolution of planetary boundary layer (PBL). And a broader rBC core mass size distribution (CMSD) can be observed in the afternoon. The CMSD show a primary mode with peak diameter (D m) of ~222 nm, and a small secondary mode with D m of ~687 nm. The average absolute coating thickness (ACT) of rBC particles is 50 nm and the bulk relative coating thickness (BRCT) is about 1.7, indicating a relatively high aging level of rBC. The correlation analysis between SP2-separated rBC and PMF-separated OA factors indicate that rBC with different core size (D c) and ACT may be originated from different sources. The rBC contributed by coal combustion is distributed throughout a large D c range (~70–500 nm). The rBC particles emitted by traffic sources have small core sizes and thin coating thickness (D c < 180 nm and ACT <50 nm); while the rBC particles emitted from biomass burning show a higher degree of aging (ACT >250 nm). In addition, the secondary mode of rBC particles are likely to be originated from coal combustion. • High concentration of rBC with relatively high aging level was observed in the North China Plain • The rBC core mass size distribution was bimodal distribution with a small secondary mode at ~687 nm • The secondary mode of rBC was likely to be contributed by coal combustion [ABSTRACT FROM AUTHOR]

The CrCoNi medium-entropy alloy is found to exhibit higher incipient plastic strength by slow cooling after the homogenization treatment. Compared with water quenching, this strengthening originates from the inconsistency of the residual stress and short-range orderings (SROs). By deconvolution of the density distribution of the critical shear stress for the first pop-in, two peaks corresponding to homogeneous and heterogeneous dislocation nucleation, respectively, are suggested. Combining the mean, areal fraction, and activation volume of the two peaks, the roles of residual stress and SROs were quantified. Here, for SRO that increases the critical shear stress for heterogeneous and homogeneous nucleation by 22.4% and 39.9%, the residual stress is negligible for the 2.1% strengthening of both. As a result, slow cooling promotes the formation of SRO in CrCoNi, which is of immense benefit to elevate its properties. [ABSTRACT FROM AUTHOR]

This study presents a comprehensive assessment of various methods for extreme value analysis of non-Gaussian wind effects using short-term time history samples. The methods examined are peaks-over-threshold (POT) method, the average conditional exceedance rate (ACER) method, and the translation process method with various translation models. The long-term wind pressure coefficient data on a saddle-shaped large-span roof collected from wind tunnel test are used as the basis for comparison. These pressure coefficient data are featured by a variety of non-Gaussian characteristics, including mildly and strongly softening and hardening non-Gaussian processes with unique distributions. Some new developments of the methods are also presented to better predict the extreme value distribution taking into account the non-Gaussian characteristics. The declustering of process to extract independent peaks over a given threshold for POT method is discussed. The effectiveness of the ACER method is firstly examined as applied to non-Gaussian wind pressures. Regarding the translation process method, this study highlights the limitations of widely used moment-based method and the method based on three-parameter gamma distribution of the process. A mixture distribution model is introduced for better modeling the distribution tail and estimation of extreme value distribution. This mixture distribution method and the method based on curve-fitting of translation function derived from mapping of cumulative distribution functions are illustrated to be capable of capturing the upper tail of translation function, thus lead to satisfactory estimations of extreme statistics for a variety of non-Gaussian processes. [ABSTRACT FROM AUTHOR]

Abstract: The dynamics and vertical distribution patterns of chlorophyll a and motile phytoplankton species in relation to the vertical stratification and its spatial and temporal variations were analyzed on the basis of observational data collected in the Gulf of Finland in July 2010. Bimodal vertical distribution of phytoplankton characterized by a thick maximum in the upper 10m layer and a thin maximum in the deeper part of the thermocline, where the chlorophyll a fluorescence values often exceeded those in the upper layer, was observed in the areas of locally weaker stratification at the mesoscale in the second half of July. We suggest that the observed bimodal distribution pattern was a result of the downward migration of phytoplankton through the thermocline at night and asynchronous upward movement of cells with a migration cycle longer than 24h. The main species found in the sub-surface maxima were the dinoflagellates Heterocapsa triquetra and occasionally Dinophysis acuminata. Biomass of H. triquetra increased in the surface layer concurrently with the appearance of sub-surface biomass maxima under conditions of relatively high horizontal variability of vertical stratification at the mesoscale. It supports our suggestion that the mesoscale dynamics favors successful vertical migration of this species between the surface layer and deep nitrate reserves. Sub-surface maxima of phytoplankton biomass, as well as vertical migration, leading to selective transport of nutrients, have to be taken into account in the regional ecosystem models, both to forecast phytoplankton blooms and describe more precisely the seasonal dynamics of nutrients and phytoplankton primary production in the stratified estuaries. [Copyright &y& Elsevier]

Due to urbanization and industrialization, PM 2.5 (particulate matter with a diameter less than 2.5 μm) pollution has become a serious environmental problem. The low spatial resolution and insufficient coverage of PM 2.5 observation stations affect research on pollution causes and human health risks. With the launch of FY-4A, new generation of Chinese geostationary weather satellites, it is possible to obtain PM 2.5 with high temporal and spatial resolution covering all China. In this study, FY-4A top-of-the-atmosphere reflectance data, meteorological factors, and geographic information were input into the deep forest (DF) model to obtain the hourly PM 2.5 in China. The samples based 10-fold cross validation of DF with an hourly R2 of 0.83–0.88, and the root mean square error is 8.81–14.7 μg/m3, while the R2 of the 10-fold cross validation result based on sites was 0.77. The monthly (R2 = 0.98) and seasonal (R2 = 0.99) estimated results showed high consistency with the observations. Feature importance showed that the contribution of estimated features to the model varies with regions and seasons. Estimation results indicated the substantial spatiotemporal differences in PM 2.5 , and pollution was the highest between 09:00–10:00 and then gradually decreased. Regions with highest pollution of PM 2.5 in China were mainly distributed in the Tarim Basin and Central China. The pollution assessment results in China indicated that: 1) In more than 80% of the winter days PM 2.5 was higher than the World Health Organization interim target 3 (37.5 μg/m3); 2) The bimodal distribution of PM 2.5 indicated that there are obvious differences in pollution between cities and suburbs; 3) In autumn and winter, the regions where population-weighted PM 2.5 was higher than IT-3 were mainly in Beijing-Tianjin-Hebei, Central China, Guanzhong Plain, Sichuan Basin, and Yangtze River Delta. Our results showed that FY-4A has advantages of high resolution and coverage and thus shows great potential for estimating pollutants. • FY-4 TOAR data were used to estimate PM 2.5 covering the whole of China. • Deep forest model performed well, with an R2 of 0.83–0.88 and RMSE of 8.81–14.7 μg/m3. • Under different conditions, the contribution of features to the model changes. • PM 2.5 concentration showed bimodal distribution characteristics. • PM 2.5 on more than 80% of days in winter was higher than the WHO interim target 3. [ABSTRACT FROM AUTHOR]

This study reports the successful crack-free fabrication of the non-weldable high γʹ Ni-superalloy IN 738 by laser powder bed fusion. The as-fabricated texture was composed of columnar grains with preferred orientation along <100> direction. Scanning electron microscopy and X-ray diffraction analysis revealed the presence of M(Ti, Ta, W, Mo, Nb)C and M(Cr, Mo, W) 23 C 6 carbides along the grain boundaries. A heat treatment used for IN 738 castings yielded a bimodal distribution of γʹ precipitates with a primary γʹ volume of 25% and size of ∼226 nm and secondary γʹ with a volume of 43% and a size of ∼88 nm. The carbides observed in the as-built condition were maintained. The heat treatment increased the hardness from 408 HV to 487 HV. The specimen exhibited an excellent room temperature yield strength, ultimate tensile strength, and elongation of 1010 MPa, 1444 MPa, and 13%, respectively. The coupons showed yield strength of 560 MPa and 388 MPa, the ultimate tensile strength of 765 MPa and 538 MPa, and an elongation of 17% and 14% at 850 °C and 927 °C, respectively. Finally, fracture analysis was used to better understand fracture behavior. [ABSTRACT FROM AUTHOR]

Abstract: 2D barcodes are widely used in many commercial applications where a scanning device is normally used to capture them. When mobile phones are used to capture 2D barcodes, the obtained images are usually distorted due to cheap camera lens and sensors, handshake and poor lighting conditions. These badly distorted images require a long decoding process which results in an error message generated or wrongly decoded information. In this paper, we propose a two-stage quality measure for the mobile phone captured 2D barcodes in order to reject those poor quality images. The proposed method is based on the global bimodal distribution features and the local finder pattern detection. Experimental results on QR code images show that the proposed two-stage quality measure has 97.64% prediction accuracy with an average run time of 110ms by rejecting distorted undecodable barcode images in advance. The proposed method also has good generalizability to “unseen” camera models and performs well under different lighting conditions. Experiments on data matrix images show that our quality measure can be extended to 2D barcode patterns with similar features. [Copyright &y& Elsevier]

Abstract: The random daytime (RDT) sampling method was employed for the assessment of average exposure on Cu, Ni and Pb, connected with the consumption of drinking water in a large water supply zone. Among three data sets of Cu, Ni and Pb concentrations determined in RDT samples (n =99) collected from the detailed study area situated in Warsaw (Poland), these related to Cu and Ni cannot be simply described by normal or log-normal distributions (in opposite to the results of Pb determinations). The general numerical method designed for the detection and calculation of mixed (bimodal) Gaussian distribution (PDF-MIX) that usually describes data taken from heterogeneous population is presented. The method is capable to extract two normal or log-normal components (PDF I and PDF II) from the mixed distribution of a given experimentally determined data set. Thus, their statistical characteristics (central values and standard deviations) can be established. Furthermore, the particular result in the obtained data set can be assigned to the individual distribution function (either PDF I or PDF II). The method was applied to the results of Cu and Ni determinations in the RDT samples. The constituents of the mixed distributions — PDF(Cu) I, PDF(Cu) II, PDF(Ni) I and PDF(Ni) II, allowed one to estimate the geometric means: 17.7μg/L, 362μg/L, 3.9μg/L and 12.1μg/L, respectively. On the basis of the above-mentioned data, the human health risk was assessed. The hazard quotient indices estimated with the use of central values of PDF(Cu) I, PDF(Cu) II, PDF(Ni) I and PDF(Ni) II log-normal distributions were: 0.013, 0.26, 0.0055 and 0.018, respectively (HQ<1 — no essential human health risk can be expected). Further statistical analysis of the data sets described by individual log-normal distributions allowed one to identify the presence of copper pipe sections in the domestic distribution systems (PDF(Cu) II) and characterize the groups of consumers who use drinking water frequently (PDF(Ni) I) or occasionally (PDF(Ni) II). [Copyright &y& Elsevier]

Abstract: Fabrication of components that require magnetic parts such as in micro motors and micro generators demands an alternative to micro machining processes that are costly and time consuming. In this study, Nd–Fe–B coatings with an average thickness of 200μm were deposited onto stainless steel substrates by an atmospheric plasma spray technique using amorphous feedstock powder of spherical morphology. The microstructure of the coatings shifted from lamellar to spherical in nature as standoff distance (SOD) increased. The total porosity of the coatings exhibited a minima with respect to SOD and ranged from 1.8 to 8.2%. Two distinct phases; i.e., the Nd-rich and Fe-rich phases, were observed and imply phase separation during the plasma spray process. Occurrence of phase separation was argued to arise due to metastable phase formation and non-equilibrium solidification. The Fe-rich phase increased with increasing SOD due to longer in-flight time allowing non-equilibrium solidification to occur. The presence of two phases results in a bimodal Weibull distribution for Vickers hardness data. However, Weibull plots for Knoop hardness and elastic modulus show monomodal behaviour. The correlation between the degree of data scattering, as reflected by the Weibull modulus, with porosity and phase percentage was determined. [Copyright &y& Elsevier]

Abstract: Megaripples in Nahal Kasuy in the southern Negev desert of Israel are characterized by a mean wavelength of about 70cm and by a bimodal distribution of coarse and fine particle sizes, the latter of which is necessary for megaripple formation. The goal of the following work was to explore long-term megaripple evolution and its dependence on wind power and directionality and to study the grain-size distribution by advanced grain-size analysis as a process indicator. Temporal dynamics of wind power such as drift potential (DP) were measured, and samples taken from megaripple crests were analyzed for grain size distribution (GSD) as the megaripple evolved from a flat bed. The GSD was initially unimodal, but it became more bimodal as the ripples grew. At the ripple crest, GSD is sensitive to storms that blow from directions perpendicular to the prevailing winds. These storms can slow the process of ripple recovery as the layer of coarse particles at the crest become finer. After two years the megaripples recovered almost fully, but a series of storms destroyed them and created small ripples in their place. Such complete ripple destruction can occur only when the megaripples are high enough (∼5cm in Nahal Kasuy), i.e., the crest must be above the saltation layer. Thus, periods of megaripple construction are ended by destructive episodes due to strong storms, and the process repeats itself. At the larger scale, the ripple dimensions of different plots may cause them to respond differently to the same storms. [Copyright &y& Elsevier]

Abstract: Background: It has been held that if bipolar disorder is categorically distinct, it should differentiate from unipolar depressive disorders by showing bimodality or a ‘zone of rarity’ in bipolar symptom scores. Two previous studies have failed to demonstrate bimodality. We undertook a third study. Methods: A total of 1106 patients attending the Black Dog Institute Depression Clinic completed the Mood Disorders Questionnaire (MDQ), in addition to undergoing clinical assessment by an Institute psychiatrist. Results: The distributions of scores for the total number of hypomanic symptoms endorsed by unipolar and bipolar patients were both skewed, with the bipolar group endorsing a high number of hypomanic symptoms and the unipolar group endorsing few symptoms — and so giving the impression of an ‘even’ distribution generated by two quite distinctly differing sub-groups. However, formal statistical analyses involving mixed modelling provided no clear evidence that a bimodal distribution provided a better fit to the data than a unimodal one. Conclusions: Failure to statistically demonstrate a ‘point of rarity’ did not marry with visual inspection of the plotted data — which clearly suggested two groups putatively capturing those with bipolar and unipolar disorders respectively. The paper considers some limitations to the emphasis on ‘bimodality’ in differentiating potentially differing conditions. [Copyright &y& Elsevier]

Abstract: The effect of oxide and nitride inclusions in a steel melt on the formation of the equiaxed grain structure during solidification of ferritic stainless steel has been investigated. The solidified grain size decreased with an increasing content of titanium. In steel samples with large solidified grains, the inclusions were generally a two-phase system in which the titanium oxide was precipitated in the liquid TiO x –Cr2O3–SiO2 matrix during cooling. Alternatively, in steel samples with fine equiaxed grains, single TiN and MgAl2O4–TiN complex particles were observed. MgO–Al2O3–TiO x ternary compounds formed in molten steel, and the spinel crystals grew at the expense of the liquid phase as the temperature decreased. Concurrently, the TiN nucleated on the surface of the MgAl2O4 particles because the lattice disregistry between MgAl2O4 and TiN was low. The formation behaviors of non-metallic compounds were successively predicted via thermochemical computation. Single mode log-normal distributions with mode particle diameters were observed in many samples, whereas a bimodal distribution was obtained in solidified samples with a fine-grained equiaxed structure. The grain sizes of the solidified samples decreased when the mean diameter of the inclusions increased. Consequently, the solidification structure can be interpreted based on the effectiveness of TiN and MgAl2O4–TiN complex inclusions as inoculants for the nucleation of -Fe. [Copyright &y& Elsevier]

Abstract: We introduce a simulated diesel particulate matter (DPM) generator which can resolve the disadvantages of conventional soot generators and be helpful in studying reduction mechanism of DPM in DPM reduction devices. Considering characteristics of DPM, the nucleation mode was reproduced with H2SO4 and benzene saturators, which can produce particles in the size range 15–30nm. The accumulation mode, which consists of particles in the size range 70–100nm, was reproduced with a carbon spark discharge generator and a benzene saturator. In our system, bimodal distributions, which commonly occur during the idling and light load operations of diesel vehicles, could be simulated at the laboratory scale by simply changing the flow rates of the carrier gas and of H2SO4. The accumulation mode, which is mainly generated at heavy engine loads without a diesel oxidation catalyst (DOC) and at light engine loads with a DOC, was also simulated by changing the applied voltage at a carbon spark discharge generator or the flow rates of the carrier gas containing the carbon particles. To evaluate the performance of the DPM generator, we measured the chemical components and morphology, and compared the size distributions of the emitted particles with them of real DPM under various engine operating conditions and sulphur contents of fuel. [Copyright &y& Elsevier]

Abstract: In spectral extinction particle sizing technique, an inversion method in the dependent model is proposed, in which the commonly used bimodal, mix-bimodal, and monomodal particle size distributions are retrieved using the bimodal Johnson''s S B function as the assumed type of distribution function. The feasibility and reliability of this inversion method are investigated, and the inversion using the bimodal modified beta function as the assumed type of distribution function is also discussed for comparison. Numerical simulations and experimental results indicate that the commonly used particle size distributions can be retrieved well using the bimodal Johnson''s S B function as a versatile distribution function in the dependent model with the spectral extinction data. This inversion method not only overcomes the difficulty caused by the inability to determine the type of specified distribution function accurately beforehand, but also allows the description of different types of distributions by a single model. [Copyright &y& Elsevier]

Abstract: An axisymmetric boundary element method (BEM) has been developed to simulate atomization processes in a pressure-swirl atomizer. Annular ligaments are pinched from the parent sheet and presumed to breakup via the linear stability model due to Ponstein. Corrections to Ponstein’s result are used to predict satellite droplet sizes formed during this process. The implementation provides a first-principles capability to simulate drop size distributions for low viscosity fluids. Results show reasonable agreement with measured droplet size distributions and the predicted SMD is 30–40% smaller than experiment. The model predicts a large number of very small droplets that cannot typically be resolved in an experimental observation of the spray. A quasi-3-D spray visualization is presented by tracking droplets in a Lagrangian fashion from their formation point within the ring-shaped ligaments. A complete simulation is provided for a case generating over 80,000 drops. [Copyright &y& Elsevier]

• A fractal model is established for reproducing the microporous structure of porous media in consideration of spatial pore distribution and the physical tortuosity, from which perspective the fractal model is superior to most of the existing models. • Analytical solutions based on the PIF model for precisely predicting the crucial parameters in different transportation processes have been obtained and validated by comparing with experimental results. • Spatial distributions of pores in realistic samples are acquired, based on which the influence of the equivalent pore distributions is specifically analyzed in the study. • The influence of specific pore size distribution on macroscopic parameters is explored, including span range of pores, dominant pore size as well as the pore bimodal distribution. A pores integrated fractal model is established to represent the microscopic structures of porous media in consideration of the spatial distribution of pores and the genuine tortuosity in various transportation processes. Transport equations are obtained based on the PIF model, providing high precision for predicting the effective thermal conductivity, the permeability and diffusion coefficient in porous materials. Spatial distributions of pores in realistic samples are acquired, based on which the influence of the equivalent pore distributions is specifically analyzed in the study. In the premise of the same porosity, broader range of pore size, dominant pores in dozens of micron or bimodal distribution of pores are crucial factors that influence the heat conduction and permeation in porous media. It is noted that the PIF model has significant values in the design of porous structure with improved transportation characteristics and in the accurate prediction of vital parameters in complex porous media. [Display omitted] [ABSTRACT FROM AUTHOR]

Nanocrystalline iron synthesized by mechanical alloying and spark plasma sintering exhibited high yield and ultimate compressive strengths of 2.59 and 3.08GPa, respectively, with a total true strain of 0.05. Partial recrystallization led to a true strain of 0.4 with a lower strength of 2.25GPa. A bimodal grain size distribution consisting of average fine grains of 2.5μm and nanograins of 85nm is attributed to the combined high strength and large plastic strain. [Copyright &y& Elsevier]

Abstract: The aim of this paper was to address the fatigue behavior and failure modes of plasma-sprayed CrC–NiCr cermet coatings in rolling contact under the identical tribological conditions of contact stress at room temperature. For all tests, the thicknesses of the coatings were controlled to be about 100μm. Thirteen rolling contact tests were performed to obtain the statistical result. The Weibull distribution plot of fatigue-life data of the coating specimens was obtained. The failure modes and mechanisms of the coatings were studied on the basis of the worn surface observations of the failed coatings. Experiment results showed that the RCF life data of the coatings exhibited high scattering, since the bimodal distribution of the fatigue-life data of the coatings was observed in the Weibull plot. Different failure modes named as spalling and delamination were observed during this investigation. However, the failure modes might be associated with the microstructure and the bonding strength of the coating, and the distribution of shear stress at the subsurface. The coatings failed in the spalling generally exhibited the relatively high fatigue lives and the coatings failed in the delamination exhibited low lives, resulting in the bimodal distribution of the fatigue-life data in the Weibull plot. [Copyright &y& Elsevier]

Abstract: Within-batch feedback control strategies are developed for the regulation of the particle size distribution (PSD) in a semibatch vinyl acetate (VAc)/butyl acrylate (BuA) emulsion copolymerization system. These strategies are also applicable for regulation of distributions in other particulate systems governed by population balances. In the first strategy, PID controllers are employed for regulating nucleation and growth events through tracking the nominal trajectories of total number of particles and the solids content by manipulating the feed-rates of the more reactive monomer, BuA, and the surfactant. The second control strategy is based on tracking nominal trajectories of the moments of the distribution with a quadratic dynamic matrix controller (QDMC). To determine the appropriate number of moments to describe the PSD during various stages of a nominal batch, a maximum-entropy approach is utilized. In the final and most complex approach, a nonlinear model predictive controller is designed utilizing the detailed population balance model of the system. The ill-conditioning resulting from the high-dimensionality of the resulting dynamical system is removed by principal component analysis (PCA)-based model order reduction and a multi-rate estimator is designed to compensate for the measurement delay associated with the PSD measurements. [Copyright &y& Elsevier]

Abstract: Rapid prototyping process called Optoform shapes functional parts from a photocurable paste. This paste contains metal powder, resin, UV photoinitiator and wetting agent. After processing on the Optoform machine, a post-treatment is applied (debinding+sintering). During the post-treatment, the residual carbon coming from the resin modifies the composition of the metal and its melting point. This modification affects densification mechanisms, which leads to a residual porosity that lowers mechanical characteristics. We will present theoretical consideration leading to the optimization of the formulation. To improve the process, bimodal powder is used and thermal treatment is adapted. [Copyright &y& Elsevier]

Abstract: A multi-rate model predictive controller algorithm is presented for the in-batch closed-loop control of the full particle size distribution (PSD) in a semibatch emulsion copolymerization system. The lack of frequent measurements of the PSD and the measurement delay of these measurements are addressed through the use of frequent density measurements from which the current conditions of the system are estimated. The high dimensionality of the discretized full PSD is reduced by the use of model order reduction based on principal component analysis. This method effectively reduces the size of the problem while preserving the main characteristics of the population balance system. Disturbances that perturb the surfactant and monomer amounts inside the semibatch vinyl acetate–butyl acrylate reactor are considered to demonstrate the performance of the proposed control algorithm. [Copyright &y& Elsevier]

Abstract: A multispecies transect-based survey with an adaptive sampling design was evaluated to determine the import of adding stations adaptively at sea in order to better resolve the cross-shelf distribution of species in regions of rapid bathymetric change. The dataset came from a series of transects occupied in November, January, March, and May from May 2003 to November 2005 along transects northeast of Hudson Canyon and northeast of Baltimore Canyon in the Mid-Atlantic Bight region of the western Atlantic. The transect survey results demonstrate the necessity of high sample density in this region of the continental shelf where fish aggregate patchily over scales of a few kilometers. Species cross-shelf distributions were often bimodal. The adaptive sampling protocol demonstrated the expected tendency of fish to be underestimated or overestimated given inadequate sampling density. However, on the average, low sample density led to an underestimation of biomass or abundance and often strongly so. Modeling of the transect design reveals that the overestimates and underestimates, as well as the bias towards underestimation, originate from variations in patch location and, even more importantly, patch shape, with the sampling design. The transect model shows that extreme overestimates and underestimates can occur when patch size is small relative to the distance between stations, but the occurrence of routine, predictable, persistent underestimates in some species is not so easily explained. The model clearly resolves the importance of bimodality and a patch form represented by a dome shape in determining the vulnerability of a species to a biomass or abundance underestimate. Cases where the fixed stations alone provide data clearly inadequate for the estimate of abundance or biomass occur when sampling density is inadequate to identify the center of the patch or to identify the shape of the patch. It is the improved understanding of patch shape that is the single most important contribution of the adaptive sampling protocol, not a better knowledge of the location of the patches. Patch shape is a principal determinant of the adequacy of sample density. [Copyright &y& Elsevier]

Abstract: Recent studies on economic growth focus on persistent inequality across countries. In this paper we study mechanisms that may give rise to such persistent inequality. We consider countries that accumulate capital in order to increase the per capita income in the long run. We show that the long-run growth dynamics of those countries can generate a twin-peak distribution of per capita income. The twin-peak distribution is caused by (1) locally increasing returns to scale and (2) capital market constraints. These two forces give rise to a twin-peaked distribution of per capita income in the long run. In our model investment decisions are separated from consumption decisions and we thus do not have to consider preferences. Empirical evidence in support of a twin-peak distribution of per capita income is provided. [Copyright &y& Elsevier]

Abstract: Measurement of frequency and field dependence of the complex magnetic susceptibility, χ(ω,H)=χ′(ω,H)−iχ″(ω,H), of water- and hydrocarbon-based magnetic fluids over the frequency range 100Hz–1MHz are presented. The magnetic polarising field, H, is initially increased from 0 to 13.6kA/m in 15 steps of approximately 900A/m and then decreases in steps from 13.6 to 0kA/m. A comparison is then made of the real and imaginary components of χ(ω) at each value of the polarising field to see if there is any significant difference between the susceptibility for increasing and decreasing polarising fields and, thus, to determine whether there is any hysteresis. Upon careful analysis of the results it is concluded that no significant hysteresis arises from the cyclic variation of H. This conclusion is supported by the results obtained in the case of the water-based fluid where, for the larger field values, a double loss-peak occurs in χ″(ω), indicating the presence of two different aggregate sizes in the sample. On decreasing H this double peak reduces to a single peak, indicating that the particles have reverted to their original state. [Copyright &y& Elsevier]

Abstract: Methylmethacrylate–butadiene–styrene (MBS) polymer blends having two different types of rubber particle distribution, monomodal and bimodal, were prepared, and their fracture properties and fracture mechanisms were investigated under quasi-static and impact loading. A fracture property, maximum J-integral J max, was evaluated at both loading-rates, and it was shown that J max values of the bimodal MBSs are much greater than that of the monomodal with small particles, and slightly better than that of the monomodal with large particles. Thick damage zones were observed in the crack-tip regions in the bimodal and monomodal with large particles, indicating larger energy dissipation during fracture initiation than in the monomodal with small particles in which damage zone is much thinner. TEM micrographs exhibit that extensive plastic deformation under quasi-static rate and multiple craze formation under impact loading rate are the primary toughening mechanisms in the bimodal MBS blends. By assessing both fracture properties and transparency, the bimodal blend with blend ratio: 2.5/7.5 (=140nm/2.35μm; total rubber particle content is 10wt%) was proved to show the best performance as MBS polymer blend with satisfiable transparency and high fracture resistance. [Copyright &y& Elsevier]