Volume Change Of Sample Research Articles

Assessing the compression properties of Gravel-bearing forest soil in northeast China’s seasonally frozen regions under Freeze-thaw cycles and varying gravel content

Due to climate change, human activities and natural disturbances in high-latitude permafrost and seasonally frozen areas are gradually increasing, attracting more attention from scholars. However, research primarily focuses on soil biology and chemistry in these regions, with limited exploration of their mechanical properties, especially compression properties. This study aims to evaluate the effects of gravel content and freeze–thaw (F-T) cycles on the compression properties of coarse-grained layered forest soil from northeast China’s seasonally frozen regions, with the goal of predicting the soil’s compressive changes under heavy mechanical loads. Specifically, using uniaxial confined compression tests (UCCT) on 252 disturbed soil samples (including two soil layers: AB and Bhs; six gravel contents; and seven F-T cycles), three characteristic compression coefficients—precompression stress (σpc), compression index (Cc), and swelling index (Cs)—were measured. Additionally, scanning electron microscopy (SEM) was used to analyze the mesostructure evolution of coarse-grained gravel-bearing soil. Volume changes of samples were measured after 15F-T cycles with varying gravel contents. Results indicate non-linear effects of gravel content and F-T cycles on σpc. Gravel content below 50% positively influences σpc, while content above 50% increases soil pore content, decreasing σpc. Cc and Cs exhibit an approximately negative correlation with gravel content and initially increase followed by a decrease with more F-T cycles. Moreover, the σpc and Cc of the AB layer are higher than those in the Bhs layer, likely due to differences in clay and organic carbon contents. Notably, the observed trends differ from previous studies on other soil types such as farmland and paddy fields. This study fills a gap in understanding the compression characteristics of layered gravel-bearing forest soil in seasonally frozen regions, providing valuable insights for evaluating soil compression in both seasonally frozen and permafrost regions, and understanding mechanical vehicle-soil interactions. It also lays the theoretical groundwork and provides data support for constructing compression models of layered gravel-bearing forest soil.

Real-time quantitative imaging of RTV silicone pyrolysis

Quantitative microstructural analysis of Room Temperature Vulcanized (RTV) silicone pyrolysis at high temperatures is presented. RTV is used as a bonding agent in multiple industries, particularly filling gaps in ablative tiles for hypersonic (re-)entry vehicles and fire prevention. Decomposition of RTV is resolved in real time using in situ high-temperature X-ray computed micro-tomography. Tomographies are acquired every 45 seconds for four different linear heating rates ranging from 7 to 54°C/min. The microstructure is resolved below 5 μm/pixel, allowing for a quantitative analysis of the micro-structural evolution and porous network development. Results are heating rate dependent, and are evaluated for bulk sample volume change, porosity, pore network size, and densification from X-ray attenuation. The outcome of this work is critical to develop multi-physics models for thermal response.

Validation of the CompactDry "Nissui" BC for Enumeration of Bacillus cereus in a Variety of Foods: AOAC Performance Tested MethodSM 092201.

The CompactDry "Nissui" BC is a ready-to-use dry media sheet using a chromogenic medium with selective agents for the detection and enumeration of Bacillus cereus in products after incubation at 30 ± 1°C for 24 ± 2 h. The CompactDry "Nissui" BC method was validated to achieve AOAC Performance Tested MethodsSM certification. The performance of the CompactDry "Nissui" BC was compared to that of ISO 7932:2004 for 10 matrixes, including panna cotta, double cream, dried baby food, dried vegetable soup mix, seafood sticks, salmon pâté, sliced ham, pork liver pâté, ham and cheese sandwich, and Caesar pasta salad with chicken and bacon. Performance indicators included repeatability, difference of means (DOM), and inclusivity/exclusivity. After log10 transformation of the data, the relative standard deviation of repeatability (RSDr) was ≤9.2% for 28 of the 30 materials (10 matrixes each at three contamination levels) analyzed by the CompactDry "Nissui" BC method and ≤13% for 27 of the 30 matrix/level combinations analyzed by the reference method. Method equivalence was demonstrated in 28 of the 30 matrix/level combinations based on the 90% confidence interval of the DOM being within (-0.5, 0.5). For inclusivity, 47 of 50 strains tested showed typical colonies and confirmed positive. For exclusivity, 28 of 33 strains tested resulted in no growth or were negative, and five were positive. Inclusivity and exclusivity results were similar on the reference method agar. The method was shown to be robust to changes in sample volume, incubation temperature, and incubation time, and data are presented supporting product consistency and 18-month shelf life. The CompactDry "Nissui" BC method is validated for the determination of Bacillus cereus in a variety of matrixes. The CompactDry "Nissui" BC method is equivalent to the ISO 7932:2004 reference method and is suitable for Performance Tested MethodsSM certification for the matrixes tested.

Development of a dynamic hollow cylinder apparatus for investigating the cyclic response of unsaturated soils subjected to stress anisotropy

The construction of most geo-structures like earthfill dams, roads, highways, embankments, and airport runways deals with the compaction of unsaturated soils under anisotropic cyclic/dynamic loadings. Many of these partially saturated geo-structures also experience three-dimensional dynamic loadings during service life. This paper presents a new hollow cylinder apparatus developed for the investigation of the cyclic response of unsaturated soils subjected to stress anisotropy. The device is unique as it enables, for the first time, studying the combined effects of stress anisotropy (effects of both parameters α and b) and the degree of saturation on the dynamic properties of unsaturated soils, the aspects that cannot be thoroughly captured using existing soil laboratory testing equipment. It allows independent control of the magnitudes and rotations of the principal stresses and measuring strains as well as control/measurement of pore water and pore air pressures in the unsaturated soil samples. The paper describes the main challenges and the adopted solutions for the development of the hollow cylinder apparatus, including the complexities associated with the non-uniformity of water content in the sample height and the measurement of the sample volume change. The relations for determining the effective stresses and strains in the unsaturated soil samples are also derived. The results of several dynamic tests on unsaturated sand over a wide range of shear strains are presented to demonstrate the capabilities of the apparatus.

Single-Step Fast Tissue Clearing of Thick Mouse Brain Tissue for Multi-Dimensional High-Resolution Imaging.

Recent advances in optical clearing techniques have dramatically improved deep tissue imaging by reducing the obscuring effects of light scattering and absorption. However, these optical clearing methods require specialized equipment or a lengthy undertaking with complex protocols that can lead to sample volume changes and distortion. In addition, the imaging of cleared tissues has limitations, such as fluorescence bleaching, harmful and foul-smelling solutions, and the difficulty of handling samples in high-viscosity refractive index (RI) matching solutions. To address the various limitations of thick tissue imaging, we developed an Aqueous high refractive Index matching and tissue Clearing solution for Imaging (termed AICI) with a one-step tissue clearing protocol that was easily made at a reasonable price in our own laboratory without any equipment. AICI can rapidly clear a 1 mm thick brain slice within 90 min with simultaneous RI matching, low viscosity, and a high refractive index (RI = 1.466), allowing the imaging of the sample without additional processing. We compared AICI with commercially available RI matching solutions, including optical clear agents (OCAs), for tissue clearing. The viscosity of AICI is closer to that of water compared with other RI matching solutions, and there was a less than 2.3% expansion in the tissue linear morphology during 24 h exposure to AICI. Moreover, AICI remained fluid over 30 days of air exposure, and the EGFP fluorescence signal was only reduced to ~65% after 10 days. AICI showed a limited clearing of brain tissue >3 mm thick. However, fine neuronal structures, such as dendritic spines and axonal boutons, could still be imaged in thick brain slices treated with AICI. Therefore, AICI is useful not only for the three-dimensional (3D) high-resolution identification of neuronal structures, but also for the examination of multiple structural imaging by neuronal distribution, projection, and gene expression in deep brain tissue. AICI is applicable beyond the imaging of fluorescent antibodies and dyes, and can clear a variety of tissue types, making it broadly useful to researchers for optical imaging applications.

Volumetric behavior of an unsaturated clayey soil-rock mixture subjected to freeze-thaw cycles: A new insight

The volumetric behavior of clayey soil-rock mixtures under freeze-thaw action is very important for the design of anti-frost heave in cold-region engineering. However, existing studies mainly focus on the effect of freeze-thaw cycles on the global volume change of fine-grained soils, and few attempts have focused on mixed soils with coarse particles such as clayey soil-rock mixtures. In this study, a series of laboratory freezing-thawing tests were conducted to investigate the effects of the freeze-thaw cycles and rock content on the global volume change, diameter change, and height change behaviors of cylindrical soil-rock mixture samples. The results demonstrate that: 1) the volumetric behavior of the samples under freeze-thaw cycles is closely related to the rock content, which is mainly because different rock contents dominate the different skeleton structures. 2) For samples with 0%, 10%, and 30% rock content, the global volume of compacted samples shows shrinkage upon freezing and expansion after thawing. However, the global volume of the sample with 50% rock content began to shrink after three freeze-thaw cycles. 3) Compared with the samples not subjected to freeze-thaw weathering, the height of samples with 0%, 10%, and 30% rock content shows shrinkage upon freezing and expansion after thawing no matter what the number of freeze-thaw cycles is. However, the diameter and height of the sample are always shrinking, regardless of whether they are frozen or thawed. 4) Upon freezing, the shrinkage of the sample's global volume and diameter tends to decrease linearly with the increase of rock content, but the shrinkage of the sample's height is not sensitive to the change of rock content. Upon thawing, the global volume and height of the sample exhibit a trend from expansion to contraction with increasing rock content, but the shrinkage of the diameter of the sample is nearly the same no matter what the rock content is. Furthermore, a computed tomography (CT)-based mesoscopic structural characteristic and two idealized schematic diagrams well illustrated the evolution mechanism of the volumetric behavior of an unsaturated clayey soil-rock mixture subjected to freeze-thaw cycles.

Observation of spin-current striction in a magnet

The interplay among magnetization and deformation of solids has long been an important issue in magnetism, the elucidation of which has made great progress in material physics. Controlling volume and shapes of matter is now indispensable to realizing various actuators for precision machinery and nanotechnology. Here, we show that the volume of a solid can be manipulated by injecting a spin current: a spin current volume effect (SVE). By using a magnet Tb0.3Dy0.7Fe2 exhibiting strong spin-lattice coupling, we demonstrate that the sample volume changes in response to a spin current injected by spin Hall effects. Theoretical calculation reflecting spin-current induced modulation of magnetization fluctuation well reproduces the experimental results. The SVE expands the scope of spintronics into making mechanical drivers.

Validation of the CompactDry "Nissui" YMR for Enumeration of Yeasts and Molds in a Variety of Foods: AOAC Performance Tested MethodSM 092002.

The CompactDry "Nissui" YMR is a ready-to-use dry media sheet using a chromogenic medium with selective agents for the detection and enumeration of yeasts and molds in products after incubation at 25 ± 1°C for 3 days. The CompactDry "Nissui" YMR method was validated in order to achieve AOAC Performance Tested MethodsSM certification. The performance of the CompactDry "Nissui" YMR was compared to that of ISO 21527-1:2008 for 10 matrixes including cooked prawns, deli vegetable salad, tuna pâté, fermented yogurt drink, spinach and ricotta quiche, egg custard tarts, fruit and vegetable smoothie, cream cheese, egg salad sandwich, and deli pasta salad. Performance indicators included repeatability, difference of means (DOM), and inclusivity/exclusivity. After log10 transformation of the data, the relative standard deviation of repeatability (RSDr) was <10% for all 30 materials (10 matrixes each at 3 levels) analyzed by the CompactDry "Nissui" YMR method and for 29 of the 30 matrix/level combinations analyzed by the reference method. The DOM ranged from -0.284 (-0.310, -0.257) log10 CFU/g to 0.307 (-0.013, 0.627) log10 CFU/g. Method equivalence was demonstrated in 29 of the 30 matrix/level combinations based on the 90% confidence interval of the DOM being within (-0.5, 0.5). All 51 inclusivity strains showed expected or atypical results, and all 32 exclusivity organisms showed no growth on the medium. The method was shown to be robust to changes in sample volume, incubation temperature, and incubation time, and data are presented supporting product consistency and a 24-month shelf life. The CompactDry "Nissui" YMR method is validated for the determination of yeasts and molds in a variety of matrixes. The CompactDry "Nissui" YMR method is equivalent to the ISO 21527-1:2008 reference method and is suitable for Performance Tested MethodsSM certification for the matrixes tested.

Soil Shrinkage Characterization of Low Plasticity Soil Using Digital Image Analysis Process

The goal of this paper is to better understand the shrinkage behavior of low plasticity (CL) soil, which is common in Warangal, India. Understanding the tensile strength and hydro-mechanical response of soil requires an understanding of the contraction behavior of soil caused by drying during wet-dry moisture cycles. With the use of simple and reliable experimental approaches, the shrinkage mechanism and behavior with suction variation are characterized and described in this study. The findings are related to the change in suction, water content, and void ratio of soil that has been air-dried from complete saturation to dryness. The proposed framework uses two simple approaches to understand soil water retention during the drying phase: one to quantify the suction potential and the other to characterize the shrinkage mechanism. In addition, the use of digital image processing (DIP) to capture sample shrinkage using a simple experimental setup is thoroughly discussed. ImageJ software has been found to be feasible for DIP and to quantify the volume change of laboratory samples. The absence of well-structured soil phases or macropores is attributable to the presence of only normal shrinkage and zero shrinkage phases in the tested soil. In terms of water–retention behavior, the shrinkage curve, and the suction curve are very similar. The effects of capillary suction on the shrinkage response of low plastic soil have been observed, emphasizing the importance of characterizing soil shrinkage behavior using suction as a stress-state variable in volume change studies.

Experimental Study on Endurance Performance of Lime and Cement-Treated Cohesive Soil

An earthwork design requires to consider the influence of severe climatic conditions on enduring performance of soils treated with chemical additives. This study was focused on investigating the mechanical behavior of a lime and cement-treated cohesive soil under the effects of repeated cycles of wetting and drying. The soil samples were prepared by adding different concentrations of cement (2, 6, 10, 12, 16, 20%) and quicklime (2, 4, 6, 8, 10%). Due to low-plastic nature of the host soil, the effectiveness of cement to reduce the plasticity of soil was relatively higher compared to lime-treatment. Likewise, an increase in optimum moisture and decrease in maximum dry unit weight was observed for both the additives and these effects were significant for lime treated soil compared to cement. Moreover, an increase in strength from 0.57 MPa to 12.9 MPa at 20% cement and from 0.57 MPa to 2.03 MPa at 2% lime was observed in unconfined compressive strengths (UCS) tests on soil samples. To investigate the durability characteristics of the treated soil, the samples were subjected to 12 cycles of wetting and drying with each cycle consisting of 5 hours of immersion in potable water and subsequent drying in oven for 43 hours. The compressive strength, volume change and weight loss of soil samples were determined at the 1st, 3rd, 6th, 9th and 12th cycle. It is observed that the durability behaviour of treated soil is multipart due to parallel processes of positive aging (hydration process associated with binding agents) and negative aging (induced weathering). For a sustainable mechanical performance of the treated soil, an optimum dose of 6% lime or 16% cement is recommended and some correlations are proposed to quantify the effects of repeated wetting and drying.

Audit of sweat chloride testing reveals analytical errors.

Sweat chloride testing (SCT) is the mainstay for the diagnosis of cystic fibrosis (CF) and biomarker in the evaluation of CFTR-modifying drugs. To be a reliable and valid tool, analytical variance (CVA) must be minimized. However, external quality assessments have revealed significant deviations in routine clinical practice. Our goal was to identify and quantify technical errors through proficiency testing and simulations. Chloride concentrations of three blinded samples (each as triplicates) were measured in 9 CF centers using a chloridometer in a routine setting. Technical errors were simulated and quantified in a series of measurements. We compared imprecision and bias before and after a counseling session by evaluating coefficients of variation (CV), adherence to tolerance limits, and inter-rater variability coefficients. Pipetting errors resulting in changes in sample volume were identified as the main source of error with deviations up to 41%. After the counseling session, the overall CVA decreased from 7.6 to 5.2%, the pass rate increased from 67 to 92%, and the inter-rater variability diminished. Significant deviations continued to be observed in individual centers. Prevention of technical errors in SCT decreases imprecision and bias. Quality assurance programs must be established in all CF centers, including staff training, standard operating procedures, and proficiency testing.

Shear strength characteristics of a sand clay liner

This study investigated shear strength behaviour of compacted sand–clay mixtures used as liners, with 10%, 20%, and 30% clay contents. A natural high-plasticity and highly expansive clay found in the eastern province of Saudi Arabia was used. A series of consolidated undrained triaxial tests and pore water pressure measurements of saturated samples with various clay contents and confining pressures was conducted using a computer-controlled Bishop and Wesley triaxial cell. The unit was equipped with pressure volume controllers and a pressure transducer for measuring sample volume changes and excess pore water pressure. The experimental test results indicate that clay content and confining pressure significantly affect stress strain response curves, pore water pressure generation curves, and steady-state shear strength. Sand–clay mixtures with clay content less than 10% showed a tendency toward contractive behaviour. The failure line slope increased in accordance with clay content increase. The deviator stress versus axial strain of saturated sand–clay mixtures indicated a hyperbolic trend. The stress ratio versus axial strain representation was more informative for the shear strength behaviour assessment. Clay content did not significantly affect critical-state friction angle. Scanning electron microscope images of the sand-clay mixtures with different clay contents are presented.

A numerical model coupling phase transformation to predict microstructure evolution and residual stress during quenching of 1045 steel

This article deals with the numerical simulation of quenching in low alloy steels based on finite element method adapting the effect of stress on the martensitic transformation to predict temperature history, microstructure evolution, and internal stresses. By superimposing the cooling curves of selected points on the CCT diagram of 1045 steel, verification of the simulated microstructures in the cylindrical specimen is carried out by comparing it with the micrographs of microstructures. Afterward, steel gears are treated in two cooling mediums to predict volume changes of gear samples quenched in oil and water. A comparison of the experimental results with those of numerical simulation generates an overall good agreement and indicates the well-demonstrated predictive capability of the model associated with kinetics of phase transformation, thermo-physical properties, and latent heat release for real-time quenching applications.

A Simple and Non-destructive Method for Chlorophyll Quantification of Chlamydomonas Cultures Using Digital Image Analysis.

Growing interest in the use of microalgae as a sustainable feedstock to support a green, circular, bio-economy has led to intensive research and development initiatives aimed at increasing algal biomass production covering a wide range of scales. At the heart of this lies a common need for rapid and accurate methods to measure algal biomass concentrations. Surrogate analytical techniques based on chlorophyll content use solvent extraction methods for chlorophyll quantification, but these methods are destructive, time consuming and require careful disposal of the resultant solvent waste. Alternative non-destructive methods based on chlorophyll fluorescence require expensive equipment and are less suitable for multiple sampling of small cultures which need to be maintained under axenic growth conditions. A simple, inexpensive and non-destructive method to estimate chlorophyll concentration of microalgal cultures in situ from digital photographs using the RGB color model is presented. Green pixel intensity and chlorophyll a, b and total chlorophyll concentration, measured by conventional means, follow a strong linear relationship (R2 = 0.985–0.988). In addition, the resulting standard curve was robust enough to accurately estimate chlorophyll concentration despite changes in sample volume, pH and low concentrations of bacterial contamination. In contrast, use of the same standard curve during nitrogen deprivation (causing the accumulation of neutral lipids) or in the presence of high quantities of bacterial contamination led to significant errors in chlorophyll estimation. The low requirement for equipment (i.e., a simple digital camera, available on smartphones) and widely available standard software for measuring pixel intensity make this method suitable for both laboratory and field-based work, particularly in situations where sample, qualified personnel and/or equipment is limited. By following the methods described here it should be possible to produce a standard curve for chlorophyll analysis in a wide range of testing conditions including different microalga cultures, culture vessel and photographic set up in any particular laboratory.

Determination of Lactose in Lactose-Free and Low-Lactose Milk, Milk Products, and Products Containing Dairy Ingredients by the LactoSens®R Amperometry Method: First Action 2020.01.

The AOAC Stakeholder Panel on Strategic Food Analytical Methods approved Standard Method Performance Requirements (SMPR®) 2018.009 for lactose in low-lactose or lactose-free milk, milk products, and products containing dairy ingredients. The LactoSens®R Method is a biosensor assay kit developed for the determination of lactose in a variety of lactose-free or low-lactose milk, dairy, and infant formula products produced with yeast-neutral lactases. In response to a call for methods, the LactoSensR method was validated in a single laboratory study with comparison to SMPR 2018.009. The LactoSensR method was evaluated for calibration, interference, repeatability, recovery, and robustness. In a method comparison study samples naturally containing low levels of lactose were evaluated using LactoSensR and an accredited high-performance anion-exchange chromatography with pulsed amperometric detection. Calibration with lactose standard solutions was shown to be linear and the method was shown to be free of interference from a variety of sugars, vitamins, alcohols, flavorings, and other compounds. Matrix studies, including 85 spiked materials, 55 products naturally containing lactose, and 13 reference materials, resulted in RSDr of 0-10.5% at 8-100 mg lactose/100 g and 0.2-5.4% at >100 mg lactose/100 g for milk and dairy products and 1.0-6.8% for infant formula, in compliance with SMPR 2018.009 with few exceptions. Recovery was 85.0-110.3% at 8-100 mg lactose/100 g and 85.6-109.7% at >100 mg lactose/100 g for milk and dairy products and 91.1-97.0% for infant formula, also meeting the performance requirements with few exceptions. The method was shown to be robust to changes in ambient temperature, sample temperature, and sample volume. The LactoSensR method compares favorably with the requirements of SMPR 2018.009 and should be adopted as a First Action AOAC Official MethodSM. The LactoSensR method is a fast, easy-to-use method that meets the requirements of SMPR 2018.009.

Geomechanical Characterization of Inclined Heterolithic Stratification Lithosome and Its Permeability Evolution under SAGD Stress Paths

SummaryA sizeable portion of the Athabasca oil sand reservoir is classified as inclined heterolithic stratification lithosomes (IHSs). However, due to the significant heterogeneity of IHSs and the minimal experimental studies on them, their hydrogeomechanical properties are relatively unknown. The main objectives of this study are investigating the geomechanical constitutive behavior of IHSs and linking their geological and mechanical characteristics to their hydraulic behavior to estimate the permeability evolution of IHSs during a steam-assisted gravity drainage (SAGD) operation. To that end, a detailed methodology for reconstitution of analog IHS specimens was developed, and a microscopic comparative study was conducted between analog and in-situ IHS samples. The SAGD-induced stress paths were experimentally simulated by running isotropic cyclic consolidation and drained triaxial shearing tests on analog IHSs. Both series of experiments were performed in conjunction with permeability tests at different strain levels, flow rates, and stress states. Additionally, an analog sample with bioturbation was tested to examine the hydrogeomechanical effects of bioturbation. Finally, the hydromechanical characteristics of analog IHS were compared with its constituent layers (sand and mud).The microscopic study showed that the layers’ integration and grain size distributions are similar in analog and in-situ IHS specimens. The results also revealed that geomechanical properties of IHSs, such as shear strength, bulk compressibility, Young's modulus, and dilation angle, are stress-state dependent. In other words, elevating the confining pressure could significantly increase the strength and elastic modulus of a sample, while decreasing the compressibility and dilation angle. In contrast, the friction angle and Poisson's ratio are not very sensitive to changes in the isotropic confining stress. An important finding of this study is that the effect of an IHS sample's volume change on permeability is contingent on the stress state and stress path. Volume change during isotropic unloading-reloading resulted in permeability increases, and sample dilation during compression shearing resulted in permeability decreases, especially at high effective confining stresses. Moreover, the tests revealed that the existence of bioturbation dramatically improves permeability of IHSs in comparison to equivalent nonbioturbated specimens but has negligible effects on its mechanical properties, which remain similar to nonbioturbated specimens. The results also showed that bioturbation had minimal impact on permeability changes during shearing. Lastly, experimental correlations were developed for each of the preceding parameters mentioned.For the first time, specialized experimental protocols have been developed that guide the infrastructure and processes required to reconstitute analog IHS specimens and conduct geomechanical testing on them. This study also delivered fundamental constitutive data to better understand the geomechanical behavior of IHS reservoir and its permeability evolution during the in-situ recovery processes. Such data can be used to accurately capture the reservoir behavior and increase the efficiency of SAGD operations in IHS reservoirs.

Investigation into the flow behavior of high-temperature ash and low-temperature ash of high calcium coal

The flow behavior of high-temperature ash (HTA) and low-temperature ash (LTA) of high calcium coal in the heating process was investigated systematically. By means of the heating stage microscope, the behavioral changes of samples were studied visually. The composition and mineral matters transformations of HTA and LTA samples were analyzed by X-ray fluorescence and X-ray diffraction. The results show that the original composition of HTA sample is different from that of LTA sample. In addition, the HTA and LTA samples experience the shrinkage, fusion and spreading processes in succession. However, the volume change of HTA sample is different from that of LTA sample. The volume of LTA sample shows a slow change at the temperature lower than 800 °C, while the volume of HTA sample is unchanged. In the temperature range of 800°C–1100 °C, the remarkable shrinkage of HTA and LTA samples are demonstrated. The formation of srebrodolskite and gehlenite attributes to this volume change. Moreover, the sharp shrinkage of HTA and LTA samples is indicated at 1100°C–1300 °C. This is caused by the formation of eutectics. Because of the diverse content and species of mineral matters in LTA sample, the volume change of LTA sample is more remarkable than that of HTA sample. The maximal shrinkages of LTA and HTA sample are 57% and 53%, respectively.

The effect of thermal oxidation on the coefficient of thermal expansion of nuclear graphite

Nuclear graphite has been used in nuclear reactors for almost 80 years, its material behavior after oxidation and irradiation is still not fully understood. In this paper, an old question of why the oxidation has a considerable effect on Young’s modulus but not on the coefficient of thermal expansion (CTE) is tried to be answered. The multi-scale finite-element method was used to analyze CTE dependence on various porosities, pore shape ratios and pore arrangements. The numerical results suggested that these factors have no significant influence on the CTE. Three different types of nuclear graphite samples were thermally oxidized at 525 °C. The microstructures of the graphite samples before and after oxidation were observed by using a laser scanning confocal microscope. The changes in sample volume, weight loss and CTE were measured after each oxidation period. The experimental results suggested that thermal oxidation at 525 °C was controlled by the in-pore diffusion-controlled regime and weight losses of up to 30% had no significant influence on CTE.

Heat capacity of 1-hexadecyl-3-methylimidazolium based ionic liquids in solid and liquid phase

In this work, two ionic liquids with a 1-hexadecyl-3-methylimidazolium cation were synthesized with different anions; chloride and saccharinate, respectively, both of them showing melting points above room temperature, ranging between (324.15 and 338.15) K and enthalpies of fusion close to or higher than 100 J/g, making them potentially suitable phase-change materials (PCMs) for latent heat storage. This application potential can be enhanced by a suitably large heat capacity and thermal conductivity of the material both in the liquid and solid phase. Heat capacity was therefore measured in this work as a function of temperature using the differential scanning calorimetry (DSC) to determine how it is affected by the anion structure. Care has been taken to evaluate the influence of the phase change on the measured data. The experimental data have then been analyzed by means of methods based on mathematical gnostics (MG). As a non-statistical approach towards data uncertainty, MG enabled us to analyze the underlying phenomena that affect the value of the experimental heat capacity. • Heat capacity for two 1-hexadecyl-3-methylimidazolium based ILs was measured in liquid and solid phase by DSC. • Two anions, chloride and saccharinate, respectively, were studied. • The influence of the sample volume and phase change was assessed by means of mathematical gnostics.

Estimation of Broadband Complex Permeability Using SIW Cavity-Based Multimodal Approach

In this article, an attractive multimodal substrate integrated waveguide (SIW) based methodology is presented for the characterization of magnetic materials in the broadband microwave frequency. The proposed approach employs a modified feed under-coupled SIW cavity instead of conventional feed over-coupled multiple SIW cavities; it uses the modified closed-form expression, developed from the first principle to consider the effect of finite sample dimensions, and mode-specific sinusoidal field variations, which were not considered before for magnetic testing using the over-coupled SIW cavity and conventional formulations. The metallic cavity borne approximations i.e., very small frequency shift for the imaginary part calculation, and very high Q-factor for the real permeability estimation are also relaxed in the modified formulations. The proposed technique is numerically verified using the full-wave electromagnetic (EM) simulator for several dispersive and nondispersive standard samples; thereafter, it is validated for the estimation of complex permeability of synthesized dispersive magnetic composites. It can characterize the dispersive magnetic composites, where the permeability value varies from paramagnetic to diamagnetic range, with improved accuracy than that of the conventional cavity perturbation approach. The modified formulation provides 34% and 12% better estimation of loss tangent and real permeability, respectively, as compared with the conventional technique. The uncertainty analysis for change in sample volume, sample misalignment, and the possible air gap is also carried out in detail. The proposed scheme typically provides more than 92% and 84% accuracy in the measured values of real permeability and loss tangent data, respectively, for various synthesized magnetic samples in broadband of microwave frequency (10-22 GHz).