Scanning Curves Research Articles

Water sorption hysteresis in wood: I review and experimental patterns – geometric characteristics of scanning curves

AbstractThe origin of sorption hysteresis in the wood-water system is still under debate. In nanoporous-fluid systems, in general, hysteresis is explained as the manifestation of metastable states in a single pore-fluid system and that is further complicated by the pore connectivity. Cell walls are considered as micro-mesoporous materials and capillary condensation in the entire hygroscopic region is proposed as an alternative sorption mechanism. In the present work, the woods of Douglas-fir, aspen and western red cedar were in focus and the pore connectivity has been investigated by observing five experimentally generated hysteresis patterns comprised by up to 4thscanning curves at 25 and 40°C. Special attention was given to the congruency property from one pattern as it is known from the literature that deviation from this property can reveal the extent of pore connectivity. Consistent patterns were found for the species-temperature combinations. Further, the high extent of congruency property indicated the dominance of independent cell wall pores.

Water sorption hysteresis in wood: II mathematical modeling – functions beyond data fitting

Abstract The Preisach model, the mathematical form of the independent domain model, has been used to describe water sorption hysteresis in wood for over 20 years, however, its geometric interpretation has not been fully explored. In this work, it is demonstrated that the geometric interpretation can be used to explain the five experimental hysteresis patterns identified in the first paper of this series. Additionally, a modification to the aforementioned model is suggested that involves a numerical implementation, which avoids the use of unknown parameters. Our approach was evaluated at 25 and 40°C by comparing the predicted 1st to 4th order scanning curves with experimental data for Douglas-fir, western red cedar and Aspen. The low prediction errors and well-maintained wiping-out property support the suitability of our approach. Compared to other models found in literature, the presented model has the advantage of high accuracy and easy implementation due to its nonparametric nature.

稀土化合物对铝合金精炼熔剂净化效率的影响

本文配置了含不同混合稀土成分的精练熔剂，以及熔剂和铝粉的混合物。研究精炼熔剂对铝熔体的精炼效果的影响，通过金相分析、熔体当中气杂含量的测定、熔剂的差示热扫描(DSC)以及动力学曲线拟合。研究结果表明含混合稀土4 g的混合精炼剂具有较低的熔点621℃，并且具有较好的精炼效果，当混合稀土添加量增加时，精炼效果降低。精炼剂中的硫酸盐对精炼效果有促进作用。 A refined flux containing different mixed rare earth elements and a mixture of flux and aluminum powder were arranged in this paper. The effect of refining agent on the refining of aluminum melt was studied by metallographic analysis, determination of gas miscellaneous content in melt, dif-ferential thermal scanning (DSC) and kinetic curve fitting of flux. The results show that the mixed refining agent with 4 g of mixed rare earth has a lower melting point of 621℃, which has a good refining effect. When the amount of mixed rare earth is increased, the refining effect is reduced. The sulphate in the refining agent has a catalytic effect on the refining effect.

Preliminary Detection of Leukemia with Blood By a Novel Electrochemical Method

InformationA simple, novel and fast electrochemical method was applied for clinical diagnosis of leukemia. Blood samples of leukemia patients were identified by screen-printed electrodes with potassium ferricyanide (III) probes. Our study successfully developed and raised the possibility of utilizing the electrodes in the identification and diagnosis of leukemia.BackgroundAccurate preliminary detection of leukemia is vital for timely and suitable chemotherapy and clinical outcomes of patients. Electrochemical methods have been widely used in cytobiology, including identification of leukemia cells. In the present study, we creatively applied the use of an electrochemical method to the analysis of human blood samples. The aim of this study was to identify leukemia, breast cancer, respiratory infection and healthy individuals by detecting the electrochemical characteristics of leukocytes in the peripheral blood of patients with a screen-printed electrode. This method might be effectively used in the preliminary screening of leukemia.MethodsA total of 99 blood samples obtained from Zhongda hospital in China (May 2016 - July 2016) were divided into four groups: healthy individuals (n = 25), respiratory infection (n=23), leukemia (n = 29) and breast cancer (n = 22). We used probes to distinguish leukocytes of people’s blood from different samples immediately due to the different electrochemical behaviors of leukocytes. A screen-printed electrode was used to measure differential pulse voltammetry by a potassium ferricyanide (III) probe combined with a simple bio-sensor system. Then, one-way analysis of variance (ANOVA) method was applied to analyze the scanning curves and peak potential and peak shifts were compared (ΔEp).ResultsThe scanning curves demonstrated the specific electrochemical behaviors of the blank potassium ferricyanide solution and which mixed with different samples in different groups. Significant differences in mean peak potentials were observed over the four groups (P< = 0.001). 105.00±8.02mV, 111.84±9.53mV, 120.90±11.18mV, 132.84±11.53mV for Group healthy, Group respiratory infection, Group leukemia, and Group breast cancer, respectively. Meanwhile, there were 4.67±3.14mV, 10.91±5.81mV,20.42±8.50mV, 33.42±10.05mV in peak shifts for above four groups respectively.ConclusionsUsing the screen-printed electrode to identify cancer was a novel method with good sensitivity and specificity. It might be effective and had a potential utility in the preliminary screening of leukemia. DisclosuresNo relevant conflicts of interest to declare.

A New Model Using Dynamic Contact Angle to Predict Hysteretic Soil Water Retention Curve

Core Ideas We predicted the initial drying, main wetting, main drying, water retention, and scanning curves. The model uses a process‐dependent contact angle determination. An experimental water retention curve was determined on clayey soils in slurry form. We present a water retention model able to predict the hysteretic response of soils during wetting–drying cycles. This model is an extension of the original Arya–Paris (AP) model. We improved the model—first by linking the empirical parameter in the AP model, a soil water retention model, to physical properties of the soil, like tortuosity, porosity, and the air‐entry point, and second by including the influence of hydraulic hysteresis through calculating the liquid–solid advancing and receding contact angles and taking into account the influence of volume change directly by considering the evolution of the soil water retention curves with void ratio variation. We assumed that the cyclic drying–wetting paths would depend on both void ratio and contact angle determination. Finally, our model performances were validated by comparison with experimental results on three soils in slurry form—two clays and a silty sand—and data from the literature for Hostun sand.

A Semi-Discrete Landweber–Kaczmarz Method for Cone Beam Tomography and Laminography Exploiting Geometric Prior Information

We present a semi-discrete Landweber–Kaczmarz method for solving linear ill-posed problems and its application to Cone Beam tomography and laminography. Using a basis function-type discretization in the image domain, we derive a semi-discrete model of the underlying scanning system. Based on this model, the proposed method provides an approximate solution of the reconstruction problem, i.e. reconstructing the density function of a given object from its projections, in suitable subspaces equipped with basis function-dependent weights. This approach intuitively allows the incorporation of additional information about the inspected object leading to a more accurate model of the X-rays through the object. Also, physical conditions of the scanning geometry, like flat detectors in computerized tomography as used in non-destructive testing applications as well as non-regular scanning curves e.g. appearing in computed laminography (CL) applications, are directly taken into account during the modeling process. Finally, numerical experiments of a typical CL application in three dimensions are provided to verify the proposed method. The introduction of geometric prior information leads to a significantly increased image quality and superior reconstructions compared to standard iterative methods.

Analyses on variations in the unsaturated characteristics of a mine waste-dump slope during rainfall

Field measurement units and a system were constructed and installed in a waste-dump slope at the Imgi mine to investigate and analyze the variations in the unsaturated characteristics of the soil. The field instrumentation system was composed of a data acquisition system, a solar system, and measuring sensors. The rainfall, matric suction, and volumetric water contents were continuously measured from the units in the instrumented site and analyzed with the soil water characteristic curve (SWCC) estimated from laboratory experiments. The variations in matric suction and volumetric water content were primarily affected by the rainfall intensity. At the surface of the slope, the largest increase and decrease in the changes in matric suction and volumetric water content were observed during the wetting and drying processes, respectively. The matric suction and volumetric water content measured from the instrumented area were compared with the SWCCs obtained from the laboratory test, and the measured data were located between the drying and wetting paths. The drying and wetting paths obtained from the laboratory test are regarded as primary drying and wetting curves, respectively. Therefore, the measured data can be defined as scanning curves, which are located between primary drying and wetting curves. The variations in matric suction according to volumetric water content were dependent on depth, and a wide range of variations was observed at shallow depths. It was confirmed that the unsaturated soil near the ground surface has the sensitive reaction induced by the infiltration and evaporation in nature.

Detection and Identification of Hematologic Malignancies and Solid Tumors by an Electrochemical Technique.

PurposeDevelop and evaluate an electrochemical method to identify healthy individuals, malignant hematopathic patients and solid tumor patients by detecting the leukocytes in whole-blood.MethodsA total of 114 individual blood samples obtained from our affiliated hospital in China (June 2015- August 2015) were divided into three groups: healthy individuals (n = 35), hematologic malignancies (n = 41) and solid tumors (n = 38). An electrochemical workstation system was used to measure differential pulse voltammetry due to the different electrochemical behaviors of leukocytes in blood samples. Then, one-way analysis of variance (ANOVA) was applied to analyze the scanning curves and to compare the peak potential and peak current.ResultsThe scanning curve demonstrated the specific electrochemical behaviors of the blank potassium ferricyanide solution and that mixed with blood samples in different groups. Significant differences in mean peak potentials of mixture and shifts (ΔEp (mV)) were observed of the three groups (P< = 0.001). 106.00±9.00 and 3.14±7.48 for Group healthy individuals, 120.90±11.18 and 18.10±8.81 for Group hematologic malignancies, 136.84±11.53 and 32.89±10.50 for Group solid tumors, respectively. In contrast, there were no significant differences in the peak currents and shifts.ConclusionsThe newly developed method to apply the electrochemical workstation system to identify hematologic malignancies and solid tumors with good sensitivity and specificity might be effective, suggesting a potential utility in clinical application.

Adsorption in heterogeneous porous media: Hierarchical and composite solids

Experiment and molecular simulation are used to investigate adsorption in heterogeneous porous media consisting of hierarchical solids (combining different porosity scales) or composite solids (such as silver nanoparticles adsorbed at the external surface of zeolite). It is shown that adsorption in such heterogeneous materials can be written as a linear combination of the adsorption isotherms in its different domains (i.e. porosity scales for the hierarchical sample and constituents for the composite sample). In the case of the composite material, we also show that the linear combination can be used with weighing parameters obtained for a different adsorbate. Such a superimposition principle, which is validated using well-characterized experimental samples, is of interest for characterization purpose as well as industrial applications as they can be used to determine accurately the amount of phases in a given sample (volume corresponding to a given porosity scale or constituent). In contrast, significant departure between the experimental adsorption isotherm and the linear combination can be used to detect coupling effects between the different domains or restrained access to a given domain type. Such a characterization strategy of complex heterogeneous media is complementary to other experiments, such as those probing capillary hysteresis shapes, scanning curves and subloops, which allow determining the distribution of domains within the framework of the independent domain theory.

Ultrafast laser ablation of soda-lime glass for fabricating microfluidic pillar array channels

Microfluidic devices constitute the key technology enabling the development of more functional lab-on-a-chip systems for medical applications. This study presents an alternative method for precisely fabricating microfluidic pillar array channels by using irradiation by an ultrashort pulse from an ultrafast laser. Unlike conventional photolithography, which requires complex procedures and techniques, the ultrafast laser process is a straightforward approach for fabricating a functional microfluidic device with multiple pulses of an ultraviolet (UV) wavelength. To satisfy the requirements of the industrial process for mass production of microfluidic devices, a picosecond (PS) laser is used as a light source. Under the optimal energy fluence of 15.28J/cm2 with a pulse overlap of 95%, the scanning curve process can be executed in the clockwise direction for forming microfluidic pillar array structures. Simultaneously, the experimental evidence shows that the ultrafast laser process produces ablated soda-lime glass channels with hydrophilic surfaces on their inner walls. Based on the processing parameters of pillar structure with the number of pulses, the value of ablation rate can be 0.04μm/pulse. This work provides a direct patterning process through which a pillar array with functional structures can be constructed within the microfluidic device.

Modeling of Horizontal Water Redistribution in an Unsaturated Soil

Core Ideas A recent laboratory experiment of horizontal water redistribution was simulated. Two different models were separately used to reproduce the measured data. Interfacial area model results showed better agreement with experimental data. When two soil samples with the same hydraulic properties but different initial water saturations are brought into contact, water will redistribute horizontally between the samples until some equilibrium is reached. The part with a higher initial saturation undergoes drainage while imbibition occurs in the other part. Hysteresis will not allow water to redistribute evenly between the two parts. In this study we used two different modeling approaches to analyze a recent experiment related to the water redistribution process. In one approach, we assumed applicability of the standard Richards equation with a hysteretic capillary pressure–saturation relationship (including scanning curves). This approach assumes continuity in the water pressure and flux across the contact surface between the two sides. In the second approach, we used an extended two‐phase flow formulation based on rational thermodynamics principles and involving the air–water specific interfacial area. For this approach, we used continuity in the Gibbs free energy for air–water interfaces and the interfacial area flux as additional conditions at the contact surface. We employed two different initial conditions: uniform initial saturation for each side and slightly nonuniform initial saturation distributions consistent with the measured water contents. We compared results of both models with measurements. The Richards equation with full hysteresis could not reproduce the measured saturation distribution unless an unrealistic value of the imbibition retention curve was assigned. The interfacial area model compared well with the experimental data after optimization of some of the model parameters.

Influence of temperature on sorption process in hemp concrete

Hemp concrete is a bio-based material which is currently undergoing a growing development. Its hygrothermal behaviour highly depends on the evolution of the moisture content which has a significant influence on heat and moisture transfer. Hysteresis phenomenon and temperature effects on sorption process make difficult the prediction of the moisture content evolution. Hysteresis phenomenon determines the equilibrium moisture content during successive adsorption/desorption cycles. Temperature influences also the equilibrium moisture content: the warmer the temperature, the lower will be the equilibrium moisture content at the same relative humidity. These two phenomena are most often neglected for modelling the moisture content evolution in heat and moisture transfer models. This can cause significant discrepancies to predict the hygrothermal response of a material subjected to climatic variations.This paper intents to contribute to the better knowledge of such sorption processes by providing new measurements and by analysing and comparing different theoretical approaches. Some adsorption and desorption main and intermediate scanning curves are measured at two different temperatures. Models taking into account these phenomena are presented. The comparison between experimental and numerical results shows that the theoretical approaches investigated are promising.

A void ratio dependent water retention curve model including hydraulic hysteresis

Past experimental evidence has shown that Water Retention Curve (WRC) evolves with mechanical stress and structural changes in soil matrix. Models currently available in the literature for capturing the volume change dependency of WRC are mainly empirical in nature requiring an extensive experimental programme for parameter identification which renders them unsuitable for practical applications. In this paper, an analytical model for the evaluation of the void ratio dependency of WRC in deformable porous media is presented. The approach proposed enables quantification of the dependency of WRC on void ratio solely based on the form of WRC at the reference void ratio and requires no additional parameters. The effect of hydraulic hysteresis on the evolution process is also incorporated in the model, an aspect rarely addressed in the literature. Expressions are presented for the evolution of main and scanning curves due to loading and change in the hydraulic path from scanning to main wetting/drying and vice versa as well as the WRC parameters such as air entry value, air expulsion value, pore size distribution index and slope of the scanning curve. The model is validated using experimental data on compacted and reconstituted soils subjected to various hydro-mechanical paths. Good agreement is obtained between model predictions and experimental data in all the cases considered.

Modelling the Hysteretic Water Retention Capacity of Soil for Reclamation Research as a Part of Underground Development

The mathematical model of the hysteretic water-retention capacity of soil is submitted. The model describes the main and scanning curves of soil drainage and moistening, as well as reversal points. Physically reasonable assumption is used to build the model. According to this assumption the function of differential moisture capacity at each point on the hysteretic curves takes only two values, which correspond to sorption and desorption equilibria of soil moisture. This assumption is consistent with the shape of the curves, which generate the water-retention capacity hysteresis loops without “pump effect”. The model parameters are interpreted based on the concepts of capillarity and lognormal distribution of the effective soil pore radii, needful for underground researches.

Hydraulic Behaviour of Unsaturated Pyroclastic Soil Observed at Different Scales

Proper soil water retention curves (SWRCs) and hydraulic conductivity functions (HCFs) are necessary for a fair analysis of groundwater flow in unsaturated slopes. In principle SWRC is hysteretic; as a consequence, laboratory characterization may not be sufficient to determine the scanning curve and the hydraulic parameters operating in situ. In this paper some results obtained by tests at different scales (testing on laboratory specimens and physical prototype and measuring in an experimental field) are presented in order to explore the hydraulic behaviour of pyroclastic soils. As regards HCF, in the paper the comparison between the hydraulic conductivity functions obtained from inverse analysis of evaporation lab tests, and the conductivity values estimated on the basis of both in situ measurements and results of tests on the aforementioned physical model is proposed. From these results, the physical prototype size (medium scale) seems to be acceptable for determinations of both SWRC and HCF.

Soil Water Retention Behaviour of a Sandy Clay Fill Material

The performance of transportation networks is critically dependent on the performance of cutting and embankment slopes. An instrumented embankment has been established at Nafferton farm in North East England to investigate the response of an embankment to changing climatic conditions. Higher pore water pressures (near to hydrostatic) were observed during winter months (typically January) falling back to lower values in March. The pore water pressures showed generally positive values in the upper 3 m of the embankment although suctions existed at 4.5 m depth. Soil water retention curves (SWRC) are essential to understand the changes in water content and suction that can take place during seasonal cycles and during extreme weather events. SWRCs for the embankment soil have been measured in the laboratory using novel high suction tensiometer based equipment. The results confirm that wetting and drying paths for the soil show significant hysteresis. The major differences occur in the first cycle of drying and wetting and smaller differences are seen in subsequent scanning curve paths.

Reversible data hiding based on histogram modification of difference images by s-type and Hilbert curve scanning

Reversible data hiding technology has currently attracted great attention recently. Using reversible data hiding methods, original cover images can be recovered losslessly from the cover image embedded information. In this paper, spatial reversible data hiding schemes based on histogram modification of difference images are discussed, in which the pixel gray values of difference image are altered slightly to perform the embedding and extraction. Specifically, we design two reversible data hiding schemes based on S-type scanning and Hilbert curve scanning, and compare them with the reversible data hiding scheme by difference between adjacent columns of the cover image. Embedding capacity and PSNR are calculated to figure out how block size, difference manner and embedding level influence the effect of hiding.

A complete soil hydraulic model accounting for capillary and adsorptive water retention, capillary and film conductivity, and hysteresis

AbstractA soil hydraulic model that considers capillary hysteretic and adsorptive water retention as well as capillary and film conductivity covering the complete soil moisture range is presented. The model was obtained by incorporating the capillary hysteresis model of Parker and Lenhard into the hydraulic model of Peters‐Durner‐Iden (PDI) as formulated for the van Genuchten (VG) retention equation. The formulation includes the following processes: capillary hysteresis accounting for air entrapment, closed scanning curves, nonhysteretic sorption of water retention onto mineral surfaces, a hysteretic function for the capillary conductivity, a nonhysteretic function for the film conductivity, and a nearly nonhysteretic function of the conductivity as a function of water content (θ) for the entire range of water contents. The proposed model only requires two additional parameters to describe hysteresis. The model was found to accurately describe observed hysteretic water retention and conductivity data for a dune sand. Using a range of published data sets, relationships could be established between the capillary water retention and film conductivity parameters. Including vapor conductivity improved conductivity descriptions in the very dry range. The resulting model allows predictions of the hydraulic conductivity from saturation until complete dryness using water retention parameters.

Water Vapour Sorption and Hysteresis Models Applicable for Silicate Building Materials

Various models of the water vapour sorption isotherms were analysed from the aspect of their applicability for silicate-based building materials like calcium-silicates, burnt clay bricks, plasters and mortars. The analysis included the assessment of the various sorption hysteresis models. They were compared and calibrated with experimental data, consisting of the main adsorption and the scanning curves. For the silicate-based building materials as a fundamental the Brunauer–Emmett–Teller (BET) and Frenkel–Halsey–Hill (FHH) models of adsorption in a combination together with Kelvin-Cohan (KC) model of desorption, with the Independent Domain Model of hysteresis can be applied due to their satisfactory universality.

Soil-water characteristics of compacted sandy and cemented soils with and without vegetation

Experiments were undertaken to study the soil-water characteristics of compacted sandy soil (SS) and cemented soil (CS) in field and laboratory conditions. The influence of vegetation and material density on the development of negative pore-water pressure (PWP) and degree of saturation (Sr) in the studied materials was investigated. The field planting experiments demonstrated a promising survival rate of Schefflera heptaphylla in both types of material, while the (SS) promoted better growth of the seedlings than the cemented one. In the field study, PWP and Srof the compacted SS responded noticeably and promptly to natural drying–wetting cycles. However, the responses in the CS were relatively mild. When subjected to the same drying–wetting cycles, PWP responded more slowly and to a smaller magnitude compared with that of the uncemented counterpart. In addition, Srchanged little in CS. An increase in the density of the SS promoted rapid development of negative PWP, while an opposite trend was observed for CS. Attempts have been made to explain the observations from the perspectives of material permeability and change in water content during a drying period in both soil types. Furthermore, in SS, the development of PWP (with a measurement limit of −90 kPa) was minimally affected by the presence of vegetation, while vegetation noticeably helped the development of negative PWP in CS. Bounds of the soil-water characteristic curve (SWCCs) of the studied materials were presented based on estimates from the drying and wetting scanning curves derived from the field monitoring. A corresponding laboratory study was carried out in an environmental chamber with controllable temperature and humidity. Monitoring results from the laboratory agreed qualitatively with those obtained from the field.