Differential Shrinkage Research Articles

Use of Melinex film for flat embedding tissue sections in LR White.

Tissue slices can undergo distortions during processing into resin for light and electron microscopy as a result of differential shrinkage of the various tissue components, and this may necessitate removal of a considerable amount of material from the final resin-embedded tissue block to ensure production of complete sections of the sample. To mitigate this problem, a number of techniques have been devised that ensure the sample is held flat during the final curing/polymerisation of the resin. For embedding in acrylic resins, oxygen must be excluded as it inhibits polymerisation, and methods devised for epoxy resin embedding are generally unsuitable. The method describes the preparation and use of air-tight flat-embedding chambers prepared from Melinex film and provides an inexpensive, technically simpler, and versatile alternative to chambers formed from either Thermanox coverslips or Aclar films that have previously been advocated for such purposes. Lay description: Tissue slices can undergo distortions during processing into resin for light and electron microscopy as a result of differential shrinkage of the various tissue components. Such distortions may necessitate removal of a considerable amount of material to ensure production of complete sections of the sample. For embedding in acrylic resins, oxygen must be excluded as it inhibits polymerisation, and methods devised for epoxy resin flat-embedding are generally unsuitable. Air-tight flat-embedding chambers prepared from either Thermanox coverslips, or a combination of PTFE-coated glass slides, polycarbonate film gaskets, and Aclar film have been advocated for such purposes. Thermanox coverslips are expensive and limited in size to 22mm × 60mm, and the alternative method is technically complicated. Melinex film is commercially available as 210mm × 297mm sheets and is approximately 1/20th the price of Thermanox and less than half the price of Aclar film. The method describes the preparation and use of embedding chambers made from Melinex film, glass slides and double-sided adhesive tape as a technically simpler, inexpensive and versatile alternative to both Thermanox coverslips and the Aclar film method.

Non-Uniform Drying Shrinkage in Robocasted Green Body Ceramic Products

The formation of defects, due to drying, in robocasted ceramic objects is an important issue arising from non-uniform shrinkage of the material during this step in the process. Common methods for shrinkage measurement are not well suited to the small size of robocasted cords or the complexity of robocasted objects. Innovative methods for shrinkage measurement were developed using non-destructive optical vision techniques with computer-controlled data acquisition, allowing measurement on millimetric cords and on specific zones of a product. The study of a single porcelain cord revealed an anisometric shrinkage related to the orientation of grains during extrusion. A differential shrinkage at the macroscopic scale was also measured on a robocasted object, indicating a moisture content gradient in the material. The methods presented in this paper are of particular relevance to real-time control of the drying process for robocasted objects.

Exploring an EM-algorithm for banded regression in computational neuroscience

Abstract Regression is a principal tool for relating brain responses to stimuli or tasks in computational neuroscience. This often involves fitting linear models with predictors that can be divided into groups, such as distinct stimulus feature subsets in encoding models or features of different neural response channels in decoding models. When fitting such models, it can be relevant to allow differential shrinkage of the different groups of regression weights. Here, we explore a framework that allows for straightforward definition and estimation of such models. We present an expectation-maximization algorithm for tuning hyperparameters that control shrinkage of groups of weights. We highlight properties, limitations, and potential use-cases of the model using simulated data. Next, we explore the model in the context of a BOLD fMRI encoding analysis and an EEG decoding analysis. Finally, we discuss cases where the model can be useful and scenarios where regularization procedures complicate model interpretation.

Creep Behavior of Fiber Reinforced Mortars and Its Effect to Reduce the Differential Shrinkage Stress

This research aims to develop durable repair materials that can resist shrinkage cracking by exploring the role of creep in reducing shrinkage stress. In this regard, the creep effect can only be quantified if an accurate creep prediction model and theoretical analysis of the shrinkage stress in the patch repair system exist. For this purpose, the research was carried out in the following sequences: first, the research investigated the short-term creep of the patch repair materials containing accelerator and micro-synthetic fibers in the 0.00–0.12% volume fraction range. This short-term creep was measured on five-cylinder specimens (having a diameter of 75 mm and a height of 275 mm). Three specimens were used to determine the deformation of the repair material under unloading conditions, while those remaining were used to determine the total deformation under loading conditions. The amount of creep deformation was determined by taking away the unloaded (shrinkage) and instantaneous (elastic) deformations from the total deformation of the loaded specimens. Secondly, a modified prediction model of ACI 209R-08 is introduced to accurately capture the rate and magnitude of the observed creep of the repair materials. Finally, a formulated theoretical analysis of shrinkage stress in the patch repair system was proposed to examine how creep potentially reduces the repair material's cracking tendency. The results show that the asymptotic value of the creep curve is attained at an earlier age and that its magnitude is greater than that of most concrete. The modified ACI 209R-08 prediction model can closely estimate the repair materials' creep behavior. The best-fit line, residual values, and coefficient of error analyses confirm the modified model's prediction accuracy. The analysis of tensile stress development in the repair layer suggests that creep can reduce stress by up to 50%. With such a reduction, the repair material is expected to be durable in resisting shrinkage and cracking tendency. Doi: 10.28991/CEJ-2023-09-08-014 Full Text: PDF

Differential carbonization-shrinkage induced hierarchically rough PAN/PDMS nanofiber composite membrane for robust multimodal superhydrophobic applications

Inducing roughness to achieve superhydrophobic surfaces through nanoparticlesʹ inclusion is a well-known concept; however, the consistency and secondary pollutants are challenges to be addressed. As a potential solution, we proposed a superhydrophobic nanofibrous membrane through the electrospinning of polyacrylonitrile and hydrophobic polydimethylsiloxane (PAN/H-PDMS) blended solution and post-heat treatment process. During carbonization, a drastic differential shrinkage between PAN and H-PDMS induces a hierarchically nanorough surface of the electrospun nanofiber. Thanks to the synergistic combination of micro-nano scale hierarchical roughness, a significant improvement in superhydrophobicity was observed with the water contact angle (WCA) of 163.48° and sliding angle (SA) of 4.2°. The proposed composite superhydrophobic nanofibrous membrane (CSN-M) exhibited excellent robustness against the tape peel, abrasion, and bending cycles by maintaining WCA higher than 158° and SA less than 6.5°. The outstanding self-healing feature recovered the WCA to 162.25° and lowered the SA to 5.0° after heat treatment at 60 °C. In addition, the CSN-M revealed a tensile modulus of 12.11 Mpa, a hydrostatic pressure of 39.18 cmH2O, and excellent breathability. The developed CSN-M is strong, with high permeability and outstanding mechano-chemical durability, making it a suitable choice for water/oil separation and self-cleaning applications.

Bioinformatics-led identification of potential biomarkers and inflammatory infiltrates in burn injury.

Burn injury is a life-threatening disease with a poor prognosis. The immune change and underlying mechanisms remain largely unknown. Thus, this study aims to find potential biomarkers and analyze the immune infiltrates after burn injury. Gene expression data of burn patients were obtained from the Gene Expression Omnibus database. Key immune-related genes were screened by differential and LASSO regression analysis. Based on key immune-related genes, patients were divided into two clusters by consensus cluster analysis. Immune infiltration was analyzed by the ssGSEA method and the immune score was calculated by the PCA method. A nomogram model was constructed based on the calculated immune score and clinical features. Finally, the expression of screened key genes was validated by an external cohort and q-PCR experiment. Fifty-nine immune-related genes were differently expressed in burn patients. After LASSO regression analysis, 12 key genes remained, namely AZU1, OLR1, RNASE2, FGF13, NR1D2, NR2E1, TLR5, CAMP, DEFA4, PGLYRP1, CTSG and CCR3. Then, patients were divided into two clusters. Immune infiltration analysis revealed that more immune cells were infiltrated and more pathways were activated in cluster A, in which patients showed high immune scores. Finally, a nomogram model was constructed and showed high accuracy and reliability. The expression pattern of 12 key genes in an external cohort and clinical samples was in accordance with the theoretical analysis results. In conclusions, this research elucidated the key role of immune response in burns and could be used as a guide for burn treatment.

STUDY ON BASIC WOOD PROPERTIES OF CRITICALLY ENDANGERED SPECIES SYZYGIUM ALBUM

Syzygium albumis a critically endangered species, and the wood basic properties haven’t been reported. Therefore, this paper analyzes the wood from the anatomical characteristics, physical properties, and secondary components.The results showed thatobserved S. albumwood of a 46-year-old tree is diffuse-porous to semi-diffuse-porous wood. The maximum vessel tangential diameter is 127.47μm, which is found at the beginning of the earlywood. Thewood rays are heteromorphic type I and II, and the multi-column part is mostly 3 cells wide. In physical properties, the air-dry density is classified as "heavy", whereas its air-dry and full-dry differential dry shrinkage are "small" and "medium", respectively. This indicates that the wood performs better when dried. The content of benzene-ethanol extract from S. albumwood is 2.10%. The benzene-ethanol extracts were analyzed by GC-MS, and the main components are 2,6,11,15-tetramethylhexadecane (3.29%), eicosamethyl cyclodecasiloxane (10.02%), octadecamethyl cyclononasiloxane (7.43%), and tetracosamethyl cyclododeca-siloxane (3.60%), etc.

Salinity induced stiffening of drying particulate film and dynamic warping

When the particle dispersion is dried, its constituents consolidate to form a solid particulate film, resulting in a transition from a liquid to a solid phase. The resultant particulate film stores the strain energy, which builds up during its formation and is often released to crack and warp. Here, we investigate the dependence of ionic strength of dispersion on the mechanical property of a resultant dried particulate film in conjunction with their role in warping. We show that the increasing ionic strength results in a faster consolidation of its constituents, increasing interparticle adhesion, thereby changing the particulate film's Young's modulus and limiting the drying induced warping. We explain this phenomenon using a theoretical model, wherein we show that the differential shrinkage during the drying in the particulate film generates the strain gradient, which later results in warping. Furthermore, our calculation shows that the curvature of a warped region is proportional to the strain gradient and is inversely proportional to the particulate film's Young's modulus.

Investigation of differential shrinkage stresses in a revolution shell structure due to the evolving parameters of concrete

Abstract The article focuses on the influence of differential shrinkage linked by drying at the early-age displacements and strain distribution of a concrete ring specimen. Depending on the gradient of dimension changes through the thickness, tensile stress occurs near the exposed surface where drying is greater and thus results in strain gradients development. An experimental design was carried out on a concrete ring cast in laboratory conditions in order to monitor strains and displacements. Subsequently, a finite element method was used to simulate the ring’s behaviour in drying conditions. The gradient development linked by a non-uniform moisture distribution in the thickness is established by solving the non-linear partial differential drying equation with Mensi’s diffusion law. The stress and displacement analysis was modeled by three nodes curved shell FEM (CSFE-sh) based on strain approximation with the shell theory. Finally, the ring’s behaviour includes both differential shrinkage resulting in the mechanical and physical properties of gradients development in the thickness and the influence of prestressing, in which the tensile creep effects have a great influence. The comparison of experimental results with numerical simulation shows that drying and tensile creep phenomena have the most important influence on the early-age stress development in the walled ring.

The effect of differential mineral shrinkage on crack formation and network geometry

Rock, concrete, and other engineered materials are often composed of several minerals that change volumetrically in response to variations in the moisture content of the local environment. Such differential shrinkage is caused by varying shrinkage rates between mineral compositions during dehydration. Using both 3D X-ray imaging of geo-architected samples and peridynamic (PD) numerical simulations, we show that the spatial distribution of the clay affects the crack network geometry with distributed clay particles yielding the most complex crack networks and percent damage (99.56%), along with a 60% reduction in material strength. We also demonstrate that crack formation, growth, coalescence, and distribution during dehydration, are controlled by the differential shrinkage rates between a highly shrinkable clay and a homogeneous mortar matrix. Sensitivity tests performed with the PD models show a clay shrinkage parameter of 0.4 yields considerable damage, and reductions in the parameter can result in a significant reduction in fracturing and an increase in material strength. Additionally, isolated clay inclusions induced localized fracturing predominantly due to debonding between the clay and matrix. These insights indicate differential shrinkage is a source of potential failure in natural and engineered barriers used to sequester anthropogenic waste.

A novel ensemble convex hull-based classification model for bevel gearbox fault diagnosis

The kernel-based geometric learning model has been successfully applied in bevel gearbox fault diagnosis. However, due to its shallow architecture and problems with its sensitivity to noise and outliers, its generalization ability and robustness need to be further improved. Ensemble learning can improve the classification accuracy of sub-classifiers, but it is effective only when the sub-classifiers meet the requirements of difference and accuracy at the same time. However, as strong classifiers, geometric learning models are difficult to produce sub-classifiers with differences. To solve these problems, this study proposes a novel ensemble model, the ensemble convex hull (CH)-based (EnCH) classification model. CH has the advantages of clear geometric meaning and is easy to deform. This paper considers the clustering characteristics of the sample points in the feature space, or both distance and density, and performs differential shrinkage deformation on the original CH. For one thing, this can produce differential CHs to build differential sub-classifiers for the ensemble. Also, it can suppress the interference of noise and outliers to improve robustness. The results of our experiments on the fault dataset of a bevel gear box indicate that the EnCH classification model can improve the generalization of the geometric learning model and has excellent tolerance to noise and outliers.

Residual Stress Measurement of a Single-step Sintered Planar Anode Supported SC-SOFC Using Fluorescence Spectroscopy

The fluorescence spectroscopy technique was used to measure the residual stress between the cathode and electrolyte of an anode supported planar single-chamber solid oxide fuel cell. The cell was made of (NiO-CGO) :(CGO) :(LSCF-CGO), as anode:electrolyte:cathode and the test was carried out after sintering at room temperature. The measured stress between these layers arises from the sintering stress caused by differential shrinkage from layers during sintering and the thermal expansion co-efficient mismatch between the layers during cooling. Therefore, the residual stress in the cathode and electrolyte layer of the cell due to co-efficient of thermal expansion mismatch during cooling was calculated analytically so as to find sintering stress. According to findings a maximum compressive residual stress of -1084 MPa occurred at the place contiguous to electrolyte layer. The estimated residual stresses in the cell’s cathode and electrolyte layer owing to CTE mismatch for the duration of cooling was calculated as -324 MPa and 15.96 MPa, respectfully. Furthermore, total mean residual compressive stress between cathode and electrolyte was obtained from fluorescence spectroscopy as -703.795. Thus, the main contribution of this residual stress is the stress growth during sintering (-395.755 MPa) due to different shrinkage behavior of adjacent layers.

Study on the threshold interfacial shear stiffness of simply supported composite girders

The strength-based categorization of composite action, which is adopted by most current specifications, may not be applicable in the deflection calculation of bridge girders. Therefore, this paper defines the threshold stiffness as the minimum required shear stiffness at the steel–concrete interface for a composite girder to be regarded as full shear interaction in deflection calculation. To determine the threshold stiffness of simply supported composite girder with a two-step arrangement of shear connectors, based on the elastic theoretical model of composite girders considering slip, two lower-bound scenarios were analyzed, and the relationship between the midspan deflection and the interfacial stiffness was first derived. Next, by controlling the deflection differences between full shear interaction and proposed scenarios to be below 5%, the equations of the threshold stiffness were derived under concentrated load, uniformly distributed load and differential thermal effects or shrinkage. The equations were then verified with a large number of finite element models. The effects of span-to-web height ratios, concrete-to-steel area ratios, and connector arrangements were analyzed within the common design range. The results show that the threshold stiffness equations are in good agreement with the finite element results. For the investigated load cases, the threshold stiffness is the highest when subjected to a concentrated load at midspan. The threshold stiffness decreases with increases in the span-to-web height ratio and the web height, and increases with the width of the concrete slab and the flange thickness, among which the span-to-web height ratio has the most significant effect. The main feature of the proposed equations is that they can consider any uniform or two-step distribution of shear connectors, which cover most cases in simply supported composite bridge girders.

Characterization of Acoustic Emissions From Analogue Rocks Using Sparse Regression‐DMDc

Moisture loss in rock is known to generate acoustic emissions (AE). Phenomena that result in AE during drying are related to the movement of fluids through the pores and induced-cracks that arise from differential mineral shrinkage, especially in clay-bearing rock. AE from the movement of fluids occurs from the reconfiguration of fluid interfaces during drying, while AE from mineral shrinkage involves the debonding within or between minerals. Here, analogue rock samples were used to examine the differences in the AE signatures when one or both AE source-types are present. An unsupervised sparse regression model, Dynamic Mode Decomposition with control, that extends Dynamic Mode Decomposition is used to characterize the AE signals recorded during the drying of porous analogue rock samples fabricated with ordinary Portland cement, with and without clay. This method can effectively and accurately reconstruct acoustic signals emitted from samples that only experience moisture loss without cracking. However, the method struggles to reconstruct signals from samples with intricate crack networks that formed during drying because AE generating mechanisms can emit contemporaneously, and the resulting waves propagate through drying-induced cracks that can lead to multiple internal reflections. Thus, the differential reconstruction accuracy of time series generated by different underlying physical processes provides a robust filter for reducing large data catalogs. In general, both dynamics and sparse initiating events are learned directly from data and this method exposes a data hierarchy based on the complexity of the intrinsic dynamics.

Experimental and analytical study of timber-timber composite (TTC) beams subjected to long-term loads

Eight TTC beams were fabricated by connecting cross-laminated timber (CLT) slab panels to laminated veneer lumber (LVL) or glued laminated timber (GLT) joists and the TTC beams were subjected to a constant sustained load and monitored over 540 days in an indoor uncontrolled environment. Benchmark experimental data for validation of numerical and analytical models were produced and effect of joist type (LVL or GLT), CLT slab thickness (60 mm or 100 mm) and orientation (crosswise or lengthwise), and type and size of shear connectors (8- or 12-mm screws) on the long-term performance of the TTC beams were studied. The creep deformation factors obtained from experimental results were in the range of 0.39–0.73. Simplified analytical models available in the literature were modified and utilised to predict the mid-span deflections of the TTC beams. The midspan deflections predicted by the simplified models had good agreement with the test data. The inelastic strains due to (differential) shrinkage between the slabs and joists had minor (less than 3%) influence on the long-term deflections predicted by the models. The analytically estimated creep deformation factor for 50-year design life of the TTC floors was in the range of 0.55–1.26 that was slightly higher than the values obtained from the EC5 approach.

Strengthening of concrete structures with ultra high performance fiber reinforced concrete (UHPFRC): A critical review

Ultra-High Performance Fiber-Reinforced Concrete (UHPFRC) is, due to its superior mechanical properties and low permeability, a promising material for the restoration and improvement of the mechanical resistance and durability of existing Reinforced Concrete (RC) structures. This paper reviews the strengthening applications of UHPFRC in flexure, shear and punching shear, with a focus on shear performance of hybrid structures and the UHPFRC-concrete interface behavior which is governing the response of the hybrid beams. Holistic review approach is adopted considering not only structural behaviour of hybrid UHPFRC-concrete beams at the macro-scale, but also parameters governing the interface behaviour between concrete and UHPFRC at the meso- and micro-scale. Current analytical and numerical methods to predict the shear or punching shear capacity of RC structures strengthened with UHPFRC are reviewed and critically analyzed. Furthermore, the frequently overlooked role of interface, the effects of bonding technique, moisture exchange between the two materials, differential shrinkage and the role of coupled environmental and mechanical loads are discussed. It is observed that although extensive research work has been conducted to study the performance of hybrid UHPFRC-concrete structures, poor understanding of the behavior at the interface between concrete and UHPFRC, the role of thermal and hygral gradients and stress concentration for premature debonding, and the lack of reliable models and design codes impede the wide application of UHPFRC.

Microstructural examination of carbonated 3D-printed concrete.

The recent interest in 3D printing with concrete has generated great interest on how inhomogeneities arise and affect performance parameters, in particular strength and durability. With respect to durability, of particular interest is how 3D‐printed layer interfaces can impact transport of species of interest, such as moisture, chlorides or carbon dioxide in carbonation processes. This is of particular interest considering that the primary use case of 3D‐printed concrete has been as a lost formwork for a cast structural concrete, and thus it is of interest to determine the carbonation resistance. This study consists of a preliminary look at the microstructure after accelerated carbonation of a 3D‐printed concrete used as a lost formwork. Preferential carbonation is observed in the layer interfaces compared to the bulk of the printed filaments, possibly related to porosity from air voids or a locally high capillary porosity corresponding to the lubrication layer.

Numerical Study of Residual Stresses Due to External Cooling in Extruded Polymer Profiles

AbstractProfile extrusion is a production technique to make polymer profiles and hollow tubes. At a certain distance after the die exit the polymer extrudate is guided into a cooling chamber, where the polymer is cooled extensively to set the part dimensions. Uniform cooling in the cooling chamber is required to avoid warpage and twisting of the extrudate due to differential shrinkage. The effect of extrudate cooling on the shape of the extrudate and the residual stresses in the final extrudate product are numerically studied. Two different cases are studied: a 2D axisymmetric problem of a viscoelastic fluid exiting an annular die and a 3D problem of a hollow square shaped die. The extrudate is extensively cooled from a distance from the die exit. Extrudate cooling is modeled by subjecting the extrudate to heat loss via convection. For the Nusselt number Nu is fixed to 1 to represent the part of the extrudate in between the die exit and the entrance of the cooling chamber. For the Nusselt number is varied to mimic different cooling speeds. The Weissenberg number Wi, the Nusselt number and are varied in this work. Results show that for high values of Wi a significant skin‐effect of high residual stresses appear near the extrudate edges for high Nusselt numbers and small values of . It is also shown that for high Weissenberg numbers the shape of the extrudate is significantly altered due to extrudate swell, when the extrudate is cooled slower. For fast cooling and small values of , the polymer does not have time to relax and the elastic stresses are “frozen in.” This leads to less extrudate swell but large residual stresses near the extrudate edges.

Ultra-fast high temperature sintering (UHS) of Li1.5Al0.5Ge1.5P3O12 electrolyte: A rationalization of the heating schedule

The renewed interest on Fast Firing has been motivated by the suppressed Li, Na volatilization during the short sintering cycle (a few seconds). Ultra-fast high temperature sintering represents the latest development in Fast Firing with heating rates approaching 104 °C/min. At present, there is no clear indication on how heating rate should be modulated to target a certain physical property. In this work, we compared different heating schedules to consolidate Li1.5Al0.5Ge1.5P3O12 electrolyte. Ultra-fast high temperature sintering carried under a single step current mode promoted the formation of radial cracks around the edge of the sample as a result of the differential shrinkage resulting from the inward heat fluxes. Multistep processing, based on the hybrid combination of conventional sintering (pre-sintering step) followed by UHS resulted in crack free samples. Under a discharge time as short as 160 s, hybrid UHS resulted in a relative density as high as 94.62% and conductivity of 1.72 × 10−4 S/cm, surpassing conventional sintered counterparts.

On the dendrite deformation and evolution mechanism of Ni-based superalloy during directional solidification

The dendritic growth in a novel casting with complex solidification path during directional solidification was investigated by experiment and simulation. The different dendrite deformations were found in the side strip and the corner, and the misorientation was measured by electron backscattered diffraction. The dendrite deformation in the local strip above each platform causes the cumulative deviation of dendrite direction in the whole strip, and this deformation is caused by the differential thermal shrinkage between upper and lower cross-sections. In addition, the dendrite with incomplete trunk concentrately deformed in the corner, and the deviation direction is consistent with its branches toward the platform, indicating that the deformation occurs before branching and thereby thermal concentrated stress is excluded. The simulation results confirm the occurrence of horizontal shrinkage stress in the mushy zone of the platform when the dendrites in the sidebar leave the platform, and also determine that the dendrite branches occur before the effect of the thermal concentration stress in the corner.