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Prediction of residual stresses in adhesively bonded joints is a major topic among practitioners, as they significantly contribute to failure. The experimental determination of relevant material properties, like shrinkage, modulus development, and relaxation behavior, is considered highly complex. Viscoelastic and numerical models are often simplified to suit specific applications. However, most of them do not consider all relevant parameters or limited portions of the curing process. This publication addresses the lack of experimental methods to determine cure-dependent properties of reactive adhesives to use them as input for FE modelling to predict cure-induced stresses. The authors focus on extended rotational rheometry (ExRheo), to determine shrinkage, shear modulus, and relaxation in dependency of curing time for three adhesives. The relationship between change of viscoelastic properties, shrinkage, and curing degree is determined through DSC and kinetic modelling. The experimental results are modelled to be implemented in a numerical analysis in order to predict cure-induced stresses in constrained rheological experiment in ExRheo. Numerical results show very good agreement with the experiments, which validate the methodology. For the first time, shrinkage induced residual stresses are modelled ab initio over the curing process, without any assumptions, solely based upon direct experimental data using a single device.

3D reconstruction and 2D observation were conducted to characterize the microstructure of the castings produced through high pressure die casting with different parameters. Our results indicate that shrinkage pores generally co-existed with externally solidified crystals (ESCs). In specimen produced without fast slow shot speed, big net-shrinkage pores accompanied with ESCs were found in the center of the specimen. When the casting pressurization was introduced, the shrinkage pores gathered to the specimen center and became much less due to the optimization of melt feeding. Much more porosity was found near the gate rather than in the middle of the rod bar, especially gas pores. The filling process simulation reveals that the middle position of the bars was firstly filled and followed by the near gate position accompanied with one intense turbulent flow.

Aims Multinomial logistic regression models allow one to predict the risk of a categorical outcome with > 2 categories. When developing such a model, researchers should ensure the number of participants ([Formula: see text]) is appropriate relative to the number of events ([Formula: see text]) and the number of predictor parameters ([Formula: see text]) for each category k. We propose three criteria to determine the minimum n required in light of existing criteria developed for binary outcomes. Proposed criteria The first criterion aims to minimise the model overfitting. The second aims to minimise the difference between the observed and adjusted [Formula: see text] Nagelkerke. The third criterion aims to ensure the overall risk is estimated precisely. For criterion (i), we show the sample size must be based on the anticipated Cox-snell [Formula: see text] of distinct ‘one-to-one’ logistic regression models corresponding to the sub-models of the multinomial logistic regression, rather than on the overall Cox-snell [Formula: see text] of the multinomial logistic regression. Evaluation of criteria We tested the performance of the proposed criteria (i) through a simulation study and found that it resulted in the desired level of overfitting. Criterion (ii) and (iii) were natural extensions from previously proposed criteria for binary outcomes and did not require evaluation through simulation. Summary We illustrated how to implement the sample size criteria through a worked example considering the development of a multinomial risk prediction model for tumour type when presented with an ovarian mass. Code is provided for the simulation and worked example. We will embed our proposed criteria within the pmsampsize R library and Stata modules.

One-third area of India's and major part of Gujarat are covered with expansive soil having high clay content s . These soils are problematic to geotechnical engineers as it causes damage to the structure founded on them. Soil swells when they imbibe water and shrink in their volume on drying. Swelling phenomena is one of the top-most challenge faced by the foundation engineer, due to the potential danger of unpredictable movements of structures founded on such types of soils. Various innovative methods have been used to counteract the volume change problem and to safeguard the structures. The use of nano chemical to reduce swelling potential of an expansive soil is a one of the developing research areas in geotechnical engineering. In this experimental work, an attempt is made to modify the swelling potential of expansive soil by using Terrenoseal (organo silane based nano chemical). The effects of adding these chemical s on soil is characterized by various geotechnical laboratory tests such as free swell index, consistency limits, compaction characteristics, swell pressure and unconfined compression test. Further, to study the physico- chemical properties using various analytical techniques such as Fourier Transformation Infrared Spectroscopy (FT-IR), Thermo Gravimetric Analysis (TGA), Particle size analysis, wettability, etc. are performed in the laboratory. The laboratory results indicated that use of nano chemical reduced the swelling potential, shrinkage, free swell index and also increases unconfined compression strength and the maximum dry density. Analytical techniques show improvement in physico-chemical properties of the soil. pH and COD tests for treated and untreated were also performed and the results were within the permissible limits.

Estimating demand for large assortments of differentiated goods requires the specification of a demand system that is sufficiently flexible. However, flexible models are highly parameterized so estimation requires appropriate forms of regularization to avoid overfitting. In this paper, we study the specification of Bayesian shrinkage priors for pairwise product substitution parameters. We use a log-linear demand system as a leading example. Log-linear models are parameterized by own and cross-price elasticities, and the total number of elasticities grows quadratically in the number of goods. Traditional regularized estimators shrink regression coefficients towards zero which can be at odds with many economic properties of price effects. We propose a hierarchical extension of the class of global-local priors commonly used in regression modeling to allow the direction and rate of shrinkage to depend on a product classification tree. We use both simulated data and retail scanner data to show that, in the absence of a strong signal in the data, estimates of price elasticities and demand predictions can be improved by imposing shrinkage to higher-level group elasticities rather than zero.

A small area estimation method is developed for repeatedly conducted multipurpose surveys. A multilevel time-series model is proposed that uses direct estimates for the most detailed domains observed at the highest frequency of the repeated survey. A consistent set of estimates at different aggregation levels is then derived by aggregation of the model-based predictions obtained for the most detailed domains observed at the highest frequency. The model borrows strength over time and space via smooth and local level trends at different aggregation levels. The model also borrows information from auxiliary series available from registers with coefficients that can vary over both domains and time. Regional domain random effects are allowed to vary smoothly over space according to a spatial autoregressive process. To account for the diversity of domains and for more volatile time-dependence, nonnormally distributed random effects and trend innovations are used via socalled global-local shrinkage priors. A Bayesian approach is taken, and the model is estimated by MCMC simulation. The method is illustrated with an application to the Dutch Labour Force Survey to produce monthly provincial and quarterly municipal unemployment figures.

The feasibility of using a computer-vision (CV) system embedded in a hot-air dryer for non-destructive and real-time monitoring of the drying behaviour of organic apples was investigated in the present study. Apple cylinders were subjected to anti-browning treatments with different dipping solutions (water as control, trehalose (4% w/v) or trehalose + ascorbic acid (4% w/v and 1% w/v)) and dipping pressures (atmospheric, 101.3 kPa and sub-atmospheric pressure, 50 kPa) followed by drying at 60 °C to a final dry basis moisture content of 0.18 g g−1. The CV system was used as an in-line process analytical technology (PAT) tool to capture images reflecting the physico-chemical changes during product drying coupled with in-line mass changes and off-line reference analyses. The spatial and colour changes from the image analysis described well the complex and non-homogenous nature of apple drying. The results of spatial changes allowed successful development of accurate linear prediction models for moisture content as a function of area shrinkage (on scaled variables) with excellent prediction capability (|BIAS

ResumenLos sistemas de producción post-fordistas, definidos por una producción flexible y des-localizada, provocaron un cambio en la geografía de la producción. En consecuencia, se forjó una nueva dinámica en los procesos de urbanización que afectó a muchas ciudades culminando en dos tipos -a priori- antagónicos de ciudades: las shrinking cities y las ciudades globales. La definición de Tokio es controvertida. Algunas investigaciones académicas señalan la existencia del shrinkage, en tanto que la ciudad se sitúa sistemáticamente entre las primeras posiciones dentro de las ciudades globales. Este estudio de caso analiza la trayectoria de la ciudad para arrojar luz sobre el proceso que está teniendo lugar. La investigación muestra la presencia de un proceso simultáneo y desigual de crecimiento y decrecimiento, bien diferenciado del city shrinkage, ya que no evidencia las implicaciones negativas del declive. No obstante manifestaciones de deterioro y vacío urbano son apreciables en el tejido de la ciudad.AbstractPost-Fordist production systems, defined by flexible and delocalized production, brought in a shift in the geography of production. In consequence, a new dynamic in urbanization processes was forged affecting many cities across the world culminating in two -a priori- antagonistic types of cities: shrinking cities and global cities There is controversy in the definition of Tokyo, as some academic research point out the existence of the shrinking process whilst the city is consistently ranked at the forefront position within the global cities. Organized as a case study, this research analyses the city trajectory in order to shed light into the process taking place. The investigation shows the presence of a simultaneous, uneven process of growth and de-growth, well differentiated from city shrinkage as the negative.

Gefördert durch den Publikationsfonds der Universität Kassel

This paper reports research into the development of compositions of engobe coatings for ceramic bricks and investigating the influence of technological production factors on their physical and mechanical properties. The results of this work make it possible to solve the task of expanding the range and improving the operational properties of building ceramics. The data obtained have made it possible to establish physicochemical processes occurring during the formation of the phase composition and structure of engobe coatings. This has revealed the possibilities for designing engobe for various types of ceramic bricks, which differ in technological parameters of production and operational properties. The charge compositions were designed in a three-component system "refractory clay – quartz sand – cullet", taking into account the possibility of their practical implementation in large-tonnage production. It has been established that the most important condition for obtaining high-quality products is the correlation of shrinkage and temperature coefficients of linear expansion of the ceramic shard and engobe coating. To prevent various defects, these indicators should vary by no more than 10 %. The crystal-phase composition of engobe is represented by b-quartz and a small amount of devitrite, which are evenly distributed in a vitreous dense layer of coating on the surface of the ceramic shard. Distinctive features of the results relate to the fact that a solution to the problem of designing engobe coatings for ceramic bricks has been proposed and the physicochemical bases of production have been highlighted. This paper also suggests ways to achieve coordination of finely dispersed coatings with coarse-grained ceramic masses by shrinkage and thermal processes. The results reported here could be applied in typical production of face, clinker, and in some cases – ordinary brick or ceramic stone with firing temperatures of 950–1150 °C, Дослідження стосуються розробки складів ангобних покриттів для керамічної цегли та дослідження впливу технологічних факторів виробництва на їх фізико-механічні властивості. Результати роботи дозволяють вирішити проблему розширення асортименту та підвищення експлуатаційних властивостей будівельної кераміки. Отримані дані дозволили встановити фізико-хімічні процеси, що протікають при формуванні фазового складу та структури ангобних покриттів. Це розкрило можливості проєктування ангобів для різноманітних видів керамічної цегли, які відрізняються технологічними параметрами виробництва та експлуатаційними властивостями. Розробку шихтових складів здійснено у трикомпонентній системі «глина вогнетривка - пісок кварцовий - склобій» з огляду на можливість їх практичної реалізації у крупнотонажному виробництві. Встановлено, що найголовнішою умовою отримання якісної продукції є співвіднесення усадок і температурних коефіцієнтів лінійного розширення керамічного черепка та ангобного покриття. Для запобігання різноманітних дефектів ці показники мають різнитись не більше, ніж на 10%. Кристалофазовий склад ангобів представлений b-кварцом та в невеликій кількості - девітритом, які рівномірно розподілені у склоподібному щільному шарі покриття на поверхні керамічного черепка. Відмінні риси отриманих результатів у тому, що запропоновано вирішення проблеми розробки ангобних покриттів для керамічної цегли та висвітлено фізико-хімічні основи виробництва. Також у роботі запропоновано шляхи досягнення узгодження тонкодисперсних покриттів з грубозернистими керамічними масами за усадочними і термічними процесами. Отримані результати можуть бути застосовані на типових виробництвах лицьової, клінкерної, а в окремих випадках – рядової цегли або керамічного каменю з температурами випалу 950–1150°С.

Shrinkage of concrete air-dry drying begins with the outer layers, thus the interior layers are compressed and the outer layers are stretched. This own stressed state contributes to the strength the sample compression. This increase in strength is quite difficult to detect because it form increase with the strength of cement stone. In the described own stressed state creep of concrete in the outer layers with stretch appears with time, and the interior layers do in compression, which results of the size of the interior layers in decrease and of the size of the outer layers to increase. The interior layers, decreasing from shrinkage, compress the outer layers. In this sample loading compressive force will overload the outer layers, which will decrease the strength of the specimen. With time shrinkage disappear and manifested relaxation own stress consequently decreases their negative influence on the strength of concrete, and so increases strength. With water-saturation of concrete sample the opposite effect will appear. Water- saturation process begins with the surface sample. While swelling (when expending) causes the appearance of compressive own stressed in the outer layers and stretch in the interior layers. When tested in compression of the sample the outer layers will be overloaded and the strength of concrete will decrease. This stressed state causes the creep in compressed outer layers and creep in the stretched interior layers that leads to partial relaxation of own tensions. Decreasing of own stress reduces their negative impact and the strength of concrete is increased after a temporary reduction. With time the creep concrete (compressed in the core and stretched to the surface of sample) and relaxation of own stress diminishes their impact, which reduces the strength of concrete. Described the impact of own stress on strength applies to other porous materials. Such conclusions are confirmed by many experiments in which the authors explain this phenomenon by adsorption effect and capillary compression. It should also be noted that the physical mechanics of the impact of own stress on concrete strength is not substantiated., Усадка бетону повітряно-сухого висихання починається з зовнішніх шарів, саме так внутрішні шари стиснуті, а зовнішні розтягнені. Такий напружений стан сприяє підвищенню міцності зразка на стиск. З часом проявляється повзучість, що скорочує внутрішні шари і збільшує зовнішні. Внутрішні шари, скорочуючись від усадки, стискають зовнішні шари. При навантаженні такого зразка стискальною силою перевантажені будуть зовнішні шари, що призведе до зниження міцності зразка. З часом усадка загасає, проявляється релаксація власних напружень, зменшується їхній негативний вплив на міцність бетону, тому міцність зростає. При водонасиченні бетонних зразків проявляється зворотний ефект.

With the continuous increase in power demand in aerospace, shipping, electricity, and other industries, a series of manufacturing requirements such as high precision, complex structure, and thin wall have been put forward for gas turbines. Gas turbine blades are the key parts of the gas turbine. Their manufacturing accuracy directly affects the fuel economy of the gas turbine. Thus, how to improve the manufacturing accuracy of gas turbine blades has always been a hot research topic. In this study, we perform a quantitative study on the correlation between process parameters and the overall wax pattern shrinkage of gas turbine blades in the wax injection process. A prediction model based on a generalized regression neural network (GRNN) is developed with the newly defined cross-sectional features consisting of area, area ratio, and some discrete point deviations. In the qualitative analysis of the cross-sectional features, it is concluded that the highest accuracy of the wax pattern is obtained for the fourth group of experiments, which corresponds to a holding pressure of 18 bars, a holding time of 180 s, and an injection temperature of 62 °C. The prediction model is trained and tested based on small experimental data, resulting in an average RE of 1.5% for the area, an average RE of 0.58% for the area ratio, and a maximum MSE of less than 0.06 mm2for discrete point deviations. Experiments show that the GRNN prediction model constructed in this study is relatively accurate, which means that the shrinkage of the remaining major investment casting procedures can also be modeled and controlled separately to obtain turbine blades with higher accuracy.

The drying kinetics of banana slices were examined in a forced convection dryer using an infrared camera to monitor the temperature profile and drying kinetics under control conditions. The air temperature was tested at 40 °C, 50 °C, 60 °C, and 70 °C and the air velocity at 0.2 m/s, 0.5 m/s, and 0.75 m/s, with initial moisture contents of the banana ranging from 76–80% wet basis. The thicknesses of the banana slices being dried were 2, 4, 6, and 8 mm. The optimum drying conditions for the highest drying rate and best color were found to be a temperature of 70 °C, an air velocity of 0.75 m/s, a low relative humidity of 5 to 7%, and banana slices with a thickness of 2 mm. As the air temperature increased, the drying rate and shrinkage also increased. Shrinkage varies concerning moisture loss, and the reduction in radial dimension of banana slices was around 17–23% from the original slice before drying. An empirical mathematical equation was derived by applying the technique of multiple linear regression analysis to the whole dataset of the many experiments of the experimental work. The moisture diffusivity was between 7.88 × 10−10 to 1.04 × 10−10 m2/s, and the average activated energy of the banana was 34.29 kJ/mol. The experimental data were used to fit the drying models. The Midilli model was predicted to produce the closest results to the experimental data.

Streaming data provides substantial challenges for data analysis. From a computational standpoint, these challenges arise from constraints related to computer memory and processing speed. Statistically, the challenges relate to constructing procedures that can handle the so-called concept drift--the tendency of future data to have different underlying properties to current and historic data. The issue of handling structure, such as trend and periodicity, remains a difficult problem for streaming estimation. We propose the real-time adaptive component (RAC), a penalized-regression modeling framework that satisfies the computational constraints of streaming data, and provides the capability for dealing with concept drift. At the core of the estimation process are techniques from adaptive filtering. The RAC procedure adopts a specified basis to handle local structure, along with a least absolute shrinkage operator-like penalty procedure to handle over fitting. We enhance the RAC estimation procedure with a streaming anomaly detection capability. The experiments with simulated data suggest the procedure can be considered as a competitive tool for a variety of scenarios, and an illustration with real cyber-security data further demonstrates the promise of the method.

Macroalgae have many potential applications and can make important contributions to sustainability and circular economy objectives. Macroalgae are degradable high-moisture biomaterials and drying is a necessary step, but drying is an energy and capital-intensive part of their production process. This study presents convective drying curves for commercially promising fresh and saltwater species (U. ohnoi and O. intermedium), obtained over a range of industry-relevant drying gas velocities (0.3–2 m/s) and material bulk densities (33–100 kg/m3). Pragmatic diffusion-based drying models that account for the influence of drying gas velocity, material bulk density, and material shrinkage are presented. Results provide critical insights into the validity of diffusion model assumptions for compressible biomaterials and new mechanisms describing gas penetration into such materials are proposed. The drying models provided in this work demonstrate a high degree of accuracy for both species.

Through summer schools, the Laboratorio del cammino proposes a learning method based on the direct and slow experience of walking. After a period in which the pandemic prevented teaching in presence, this approach was considered even more valuable. It combines and does not replace a digital experience with one of proximity, making it possible to compare what is visible when crossing a territory with what is seen from afar. The article reports the participation in the 2021 edition of the summer school, focused on the industrial and territorial contraction of north-eastern Pied- mont. Moving around and staying in the area made it possible to reveal an articulation of open spaces that make up the countryside, which is thus highlighted concerning an image obscured by the factory. Themes and problems of agricultural and silvo-pastoral shrinkage emerge, and initiatives take care of the territory.

PM2.5 has a significant negative impact on human health and atmospheric quality, and accurate prediction of its concentration is necessary. When using common point prediction models for PM2.5 concentration prediction, the influence of various uncertainties on PM2.5 concentrations makes the prediction results suffer from poor accuracy. To address this issue, this paper proposes the quantile regression neural network (QRNN) model based on the least absolute shrinkage and selection operator (LASSO), combined with kernel density estimation (KDE) for probabilistic density prediction of PM2.5 concentrations. The model uses LASSO regression to select the influential factors, and then the quartiles of daily PM2.5 concentrations calculated by the QRNN model are imported into the KDE model to obtain the probability density predictions of PM2.5 concentrations. In the paper, empirical analyses are carried out with the cities of Beijing and Jinan in China as well as six other datasets, and the prediction performance of the model is assessed by using evaluation criteria in both point prediction and interval prediction. The simulation reveals that the predictive performance of the LASSO-QRNN-KDE model is well, and the model is not only effective in filtering high-dimensional data, but also has a higher accuracy compared to common research models. In addition, the model is able to describe the uncertainty of PM2.5 concentration fluctuations and carry more information on the variation of PM2.5 concentrations, which can provide a novel and excellent PM2.5 concentration prediction tool for relevant policy makers.

Long-term strength investigations of construction elements made of reinforced concrete (RC) under creep conditions are considered. A calculation method that allows determination of the load-bearing capacity and long-term strength of RC thin-walled elements under short- and long-term loading is proposed. The method is based on a combination of the finite-element method for solving boundary value problems at each time step and the finite-difference method for integrating the initial value problems. The numerical results are compared with experimental data obtained in the loading–unloading mode during long-term deformation. An example of creep and damage calculations in the RC coating and recommendations for parameter selections are given.

Increased temperature and carbon dioxide concentration caused by climate change will aggravate the creep shrinkage and structural durability of concrete bridges. Overloading also has a great impact on the time-dependent reliability of existing bridges. This research paper analyses the time-dependent reliability of bridges based on climate change and overload. By improving the concrete carbonation model and referring to the B4 model of concrete creep, the effects of ambient temperature and humidity on concrete under different emission-reduction scenarios were considered. At the same time, given the serious problems of vehicle overload in China, combining different overload scenarios with climate change led to the establishment of a time-dependent reliability model for precast-concrete bridges. The results showed that as the overload rate increased, the time-dependent reliability degradation rate of a case study bridge accelerated. Under the scenario considering both high greenhouse gas emissions and the maximum overload rate, the service life of the case study bridge decreased to 50% of its design life.

Plastic shrinkage cracking propagating at early ages inevitably impairs the performance of concrete structures. To mitigate this, using a recently developed shrinkage-reducing polycarboxylate superplasticiser (SR-PCA) with outstanding shrinkage-reducing and water-reducing effectiveness can be a promising approach. The present work aims to investigate the effect of SR-PCA on plastic shrinkage cracking and to clarify the underlying mechanisms. For comparison, a traditional polyether type shrinkage reducing admixture (SRA) and a polycarboxylate superplasticiser (PCA) were also used. Based on the investigations on horizontal shrinkage, settlement, bleeding, evaporation mass loss, cement hydration, surface tension of pore fluid and capillary pressure, the underlying working mechanisms of SR-PCA were identified. The results indicate that SR-PCA is able to reduce the crack area, maximum crack width and average crack width by up to 55, 48 and 50%, respectively. Furthermore, prolonging the bleeding duration and initial time of capillary pressure build-up caused by retarding the cement hydration, lowering the evaporation mass loss, and a lower development rate of capillary stresses and capillary pressure peak value induced by decreasing the surface tension of pore fluid are responsible for preventing the plastic shrinkage cracking of mortars containing SR-PCA.

This study aims to develop a material-saving performance prediction model for fast-hardening alkali-activated slag/silica fume blended pastes. The hydration process in the early stage and the microstructural properties after 24 h were analyzed using design of experiments (DoE). The experimental results show that the curing time and the FTIR wavenumber of the Si-O-T (T = Al, Si) bond in the band range of 900–1000 cm−1 after 24 h can be predicted accurately. In detailed investigations, low wavenumbers from FTIR analysis were found to correlate with reduced shrinkage. The activator exerts a quadratic and not a silica modulus-related conditioned linear influence on the performance properties. Consequently, the prediction model based on FTIR measurements proved to be suitable in evaluation tests for predicting the material properties of those binders in the building chemistry sector.

The adoption of flowable mixtures of treated soils is suggested as a sustainable solution for repairing the damage caused by burrowing animals in the Po River embankments. Soil from damaged sites is proposed to be mixed with lime or cement, other additives, and water in order to obtain mixtures with an adequate compromise between viscosity—which is crucial for flowing the mixture into the hole with site machines—and shrinkage that might occur over time according to the hole boundary conditions. Injections of soil-treated mixtures must guarantee hydraulic and mechanical continuity with the existing embankment and reduce shrinkage phenomena that frequently occur with cement–bentonite grout, which is commonly used for this purpose. This study presents an interdisciplinary experimental programme in the search for the best formulation among several recipes of mixtures of soils, collected from four embankments of Po River or its tributaries and treated with lime or cement, different percentages of water, and other additives. The mixtures, after soil classification and viscosity determinations, were then used to create samples for which shrinkage and erosion susceptibility were estimated, respectively, through a non-standard volume measurement procedure and crumb tests. An abacus will be then proposed in order to give, as a first estimation, applicative indications on the best recipe among the investigated mixtures.

The value of gem opals is compromised by their potential susceptibility to “crazing”, a phenomenon observed either in the form of whitening or cracking. To understand the latter, 26 opal samples were investigated and separated into 2 groups based on handling: “water-stored” opal samples, which are stored in water after extraction, and “air-stored” opal samples, which are stored in air for more than a year. To induce cracking, samples were thermally treated by staged heating and characterized using optical microscopy and Raman spectroscopy before and after cracking. For water-stored opals, cracking was initiated with moderate heating up to 150 °C, while for air-stored opals, higher temperatures, circa 300 °C, were required. In water-stored opals that cracked, polarized light microscopy revealed stress fields remaining around the cracks, and a red shift in the Raman bands suggested tensile stresses. These stresses were not observed in air-stored samples that cracked. Based on these observations, for air-stored samples, cracking was ascribed to super-heated water-induced decrepitation. By contrast, for water-stored samples, cracking was linked to drying shrinkage, which correlates with the anecdotal reports from the gem trade. We thus identify the physical origin of cracking, and by comparing it to current knowledge, we determine the factors leading to cracking.

The aim of this research was to study water absorption and dimensional stability of shoe insoles. The dimensional stability was indicated by swelling, increase in size of the sample, and shrinkage. Tests were performed ac¬cording to the relevant ISO standards. Eight shoe insoles with different compositions were used in the experiment. The experimental results have shown that the water absorption ability of insoles is influenced by the composition and structure of insole components. The statistical analysis of the experimental results has shown a positive linear correlation between water absorption of insole and their swelling, and a negative linear correlation between swelling and increase in size of the samples. The shrinkage of all eight insoles was less than 1%. Key words: water absorption, dimensional stability, swelling, shrinkage

We present a microfluidic technique that shrinks lipidstabilized microbubbles from O(100) to O(1) µm in diameter–the size that is desirable in applications as ultrasound contrast agents. We achieve microbubble shrinkage by utilizing vacuum channels that are adjacent to the microfluidic flow channels to extract air from the microbubbles. We tune a single parameter, the vacuum pressure, to accurately control the final microbubble size. Finally, we demonstrate that the resulting O(1) µm diameter microbubbles have similar stability to microfluidics generated microbubbles that are not exposed to vacuum shrinkage. We anticipate that, with additional scale-up, this simple approach to shrink microbubbles generated microfluidically will be desirable in ultrasound imaging and therapeutics applications.

The microstructural features of three different materials have been quantified by means of 2D image analysis and X-ray micro-computer tomography (CT) and the results were compared to determine the reliability of the 2D analysis in the material characterization. The 3D quantification of shrinkage pores and Fe-rich inclusions of an Al-Si-Cu alloy by X-ray tomography was compared with the statistical analysis of the 2D metallographic pictures and a significant difference in the results was found due to the complex morphology of shrinkage pores and Fe-rich particles. Furthermore, wood particles of a wood-plastic composite were measured by dynamic image analysis and X-ray tomography. Similar results were obtained for the maximum length of the particles, although the results of width differ considerably, which leads to a miscalculation of the particles aspect ratio. Finally, air voids of a foam concrete were investigated by the analysis of the 2D pictures in ImageJ and the results of the 2D circularity were compared with the values of the 3D elongation obtained by micro-computed tomography. The 3D analysis of the air voids in the foam concrete showed a more precise description of the morphology, although the 2D result are in good agreement with the results obtained by X-ray micro-tomography.

В даній роботі досліджено вплив напружено-деформованого стану матеріалу пресовок з порошків заліза на формування їх структури під час спікання, вплив розмірів вихідних частинок порошків на усадку та величину напружень. Розраховано мікро- і макронапруження що виникають в процесі спікання. Об’єкт дослідження: зміна напружено-деформованого стану пресовок з порошків заліза під час нагрівання Мета роботи: встановити залежність між напружено-деформованим станом, кінетикою усадки і формуванням тонкої структури порошкових матеріалів на основі порошків заліза із середнім розміром 5мкм і 100мкм. Встановлено вплив розміру частинок порошку та їх гранулометричного складу на кінетику усадки пресовок під час спікання. Встановити залежність між розміром частинок вихідного порошку, величиною залишкових напружень і розміром областей когерентного розсіювання в порошкових матеріалах під час нагрівання. На фізичних моделях методом мікроскопічного аналізу виявлені сліди пластичної деформації в області міжчастинних контактів, що формують сходинки внаслідок проковзування дислокацій. In this work, the influence of the stress-strain state of the material of pressed iron powders on the formation of their structure during sintering, the influence of dimensions on shrinkage and the magnitude of stresses is investigated. The micro- and macro stresses arising in the sintering process are calculated. The object of research: stress-deformed state of pressings from iron powders during heating The purpose of the work: to establish the relationship between the stress-strain state, the kinetics of shrinkage and the formation of a fine structure of powder materials based on iron powders with an average size of 5μm and 100μm. The effect of the size of powder particles and their particle size composition on the kinetics of shrinkage of compacts during sintering was established. To establish the relationship between the size of the particles of the original powder, the amount of residual stress and the size of the areas of coherent scattering in powder materials during heating. Traces of plastic deformation in the area of interparticle contacts forming steps as a result of slippage of dislocations were found on the physical models by the method of microscopic analysi.

The article presents the results of the analysis of the reasons for the formation of cracks in the walls of modern low-rise stone buildings erected using silicate brick masonry. The morphology of cracking in walls and partitions is shown, depending on their design features, the presence of door and window openings. It has been established that the main reason for the formation of cracks in load-bearing and self-supporting walls is tensile stresses in the masonry, caused by the constraint of its shrinkage deformations. Damage to partitions by cracks is caused by shrinkage deformations of the masonry and deflections of the floor slabs, which are the supports of the partitions. The nature of cracking of partitions depends on the ratio of their sizes, the presence and location of doorways, the method of pairing partitions with floor slabs. The crack resistance of walls and partitions is significantly affected by the quality of masonry and finishing work, masonry maintenance during its construction. В статье приведены результаты анализа причин образования трещин в стенах современных малоэтажных каменных зданий, возводимых с применением каменной кладки из силикатного кирпича. Показана морфология трещинообразования в стенах и перегородках, в зависимости от их конструктивных особенностей, наличия дверных и оконных проемов. Установлено, что основной причиной образования трещин в несущих и самонесущих стенах являются растягивающие напряжения в каменной кладке, вызванные стеснением ее усадочных деформаций. Повреждения трещинами перегородок обусловлены усадочными деформациями кладки и прогибами плит перекрытий, являющимися опорами перегородок. Характер трещинообразования перегородок зависит от отношения их размеров, наличия и места расположения дверных проемов, способа сопряжения перегородок с плитами перекрытий. На трещиностойкость стен и перегородок существенное влияние оказывает качество выполнения кладочных и отделочных работ, уход за кладкой в процессе ее возведения.

[ES] Todas estructuras, especialmente las conformadas con hormigón armado, no solo deben cumplir con la seguridad necesaria bajo los Estados Límites Últimos (ULS), además es imprescindible que garanticen un comportamiento adecuado frente a condiciones de servicio. En general, los requisitos fundamentales de servicio que debe cumplir este tipo de estructuras son: la funcionalidad, comodidad para el usuario y la apariencia. Sin embargo, estos no se pueden verificar de forma directa; por lo tanto, ha sido necesario definir criterios de desempeño tales como control de deflexión, control de vibración y control de agrietamiento para dar cumplimiento a lo indicado anteriormente. Además, se dificulta el cálculo de la capacidad de servicio debido al fenómeno de agrietamiento, el efecto de rigidez por tensión, la contracción y los efectos de fluencia. Por lo tanto, el control de la fisuración en estructuras de hormigón armado generalmente se logra limitando la tensión en el refuerzo de acero y la matriz de hormigón. Siendo así que, en los diseños incluidos en códigos relevantes a hormigón, especifican la tensión máxima del refuerzo de acero después de la fisuración y el ancho máximo de fisura para los miembros estructurales de CR o FRC, no obstante los aspectos de capacidad de servicio del diseño para el hormigón reforzado con fibras de ultra alto rendimiento reforzado (R-UHPFRC), no han sido incluidos en los códigos o recomendaciones de UHPFRC. A pesar de que se han realizado muchos esfuerzos en la investigación tanto experimental como teórica sobre el comportamiento de servicio de los elementos estructurales de CR o FRC durante las últimas décadas, para el R-UHPFRC se debe desarrollar aún más su conocimiento relacionado con los requisitos para el diseño de capacidad de servicio, incluyendo su comportamiento de tensión y agrietamiento. En este marco, el objetivo principal de la presente tesis doctoral es evaluar el comportamiento de servicio de R-UHPFRC. Por tal razón, es fundamental realizar la evaluación del comportamiento de deformación y fisuración de los elementos de tracción R-UHPFRC. Para ello, se abordaron y cumplieron adecuadamente dos puntos principales. El primero, diseñar una metodología de prueba innovadora y adecuada para ejecutar los experimentos requeridos para este proyecto de doctorado. En segundo lugar, se llevó a cabo la evaluación de la respuesta de rigidez a la tensión y el comportamiento de agrietamiento del R-UHPFCR, que son parámetros primordiales para el diseño de capacidad de servicio. Para estudiar estos dos parámetros, se consideraron algunos parámetros importantes tales como: el efecto del volumen del contenido de fibra, el tipo de fibra, el efecto del tamaño, el efecto de la relación de refuerzo y el efecto de la contracción. Finalmente, para evaluar los parámetros mencionados, se presentan cuatro campañas experimentales. Cada una de ellas, representa un nivel diferente de estudio. El primero corresponde a la validación de la metodología de ensayo de tracción propuesta y examinar los datos experimentales obtenidos, para emplearlos en futuros estudios de este proyecto. El segundo nivel consistió en establecer y realizar experimentos completos con dos tipos de fibra de acero, modificando además su cantidad, es así como se utilizaron diferentes proporciones de refuerzo y sección transversal para evaluar el efecto tanto del tamaño como del contenido de fibra, respectivamente. También, en un estudio experimental específico se indagó sobre el efecto de la combinación de micro y microfibras de acero en la deformación y el comportamiento de agrietamiento de los elementos R-UHPFRC de tracción. El tercer nivel corresponde a una prueba de contracción intensiva, necesaria para obtener el valor de contracción del UHPFRC utilizado en esta investigación. El último nivel comprende la modificación de la geometría de la probeta y el uso de probetas en forma de hueso de perro para evaluar el ancho medio y máximo de fisura (valor, [CA] Totes les estructures, especialment les conformades amb formigó armat, no només han de complir amb la seguretat necessària sota els Estats Límits Últims (ULS), a més és imprescindible que garanteixin un comportament adequat davant de condicions de servei. En general, els requisits fonamentals de servei que ha de complir aquest tipus d'estructures són: la funcionalitat, la comoditat per a l'usuari i l'aparença. Això no obstant, aquests no es poden verificar de forma directa; per tant, ha calgut definir criteris d'acompliment com ara control de deflexió, control de vibració i control d'esquerdament per a donar compliment al que s'ha indicat anteriorment. A més, es dificulta el càlcul de la capacitat de servei a causa del fenomen d'esquerdament, l'efecte de rigidesa per tensió, la contracció i els efectes de fluència. Per tant, el control de la fissuració en estructures de formigó armat generalment s'aconsegueix limitant la tensió al reforç d'acer i la matriu de formigó. És així que en els dissenys inclosos en codis rellevants a formigó, especifiquen la tensió màxima del reforç d'acer després de la fissuració i l'amplada màxima de fissura per als membres estructurals de CR o FRC, no obstant els aspectes de capacitat de servei del disseny per al formigó reforçat amb fibres d'ultra alt rendiment reforçat (R-UHPFRC), no han estat inclosos als codis o recomanacions d'UHPFRC. Tot i que s'han realitzat molts esforços en la investigació tant experimental com teòrica sobre el comportament de servei dels elements estructurals de CR o FRC durant les últimes dècades, per al R-UHPFRC s'ha de desenvolupar encara més el seu coneixement relacionat amb els requisits per al disseny de capacitat de servei, incloent el comportament de tensió i esquerdament. En aquest marc, l'bjectiu principal de la present tesi doctoral és avaluar el comportament de servei de R-UHPFRC. Per aquesta raó, és fonamental fer l'avaluació del comportament de deformació i fissuració dels elements de tracció R-UHPFRC. Per això, es van abordar i van complir adequadament dos punts principals. El primer, dissenyar una metodologia de prova innovadora i adequada per executar els experiments requerits per a aquest projecte de doctorat. En segon lloc, es va fer l'avaluació de la resposta de rigidesa a la tensió i el comportament d'esquerdament del R-UHPFCR, que són paràmetres primordials per al disseny de capacitat de servei. Per estudiar aquests dos paràmetres, es van considerar alguns paràmetres importants com ara l'efecte del volum del contingut de fibra, el tipus de fibra, l'efecte de la mida, l'efecte de la relació de reforç i l'efecte de la contracció. Finalment, per avaluar els paràmetres mencionats, es presenten quatre campanyes experimentals. Cadascuna representa un nivell diferent d'estudi. El primer correspon a la validació de la metodologia dassaig de tracció proposada i examinar les dades experimentals obtingudes, per a emprar-les en futurs estudis daquest projecte. El segon nivell va consistir a establir i realitzar experiments complets amb dos tipus de fibra d'acer, modificant-ne a més la quantitat, és així com es van utilitzar diferents proporcions de reforç i secció transversal per avaluar l'efecte tant de la mesura com del contingut de fibra, respectivament. També, en un estudi experimental específic, es va indagar sobre l'efecte de la combinació de micro i macrofibres d'acer en la deformació i el comportament d'esquerdament dels elements R-UHPFRC de tracció. El tercer nivell correspon a una prova de contracció intensiva, necessària per obtenir el valor de contracció de l'UHPFRC utilitzat en aquesta investigació. L'últim nivell comprèn la modificació de la geometria de la proveta i l'ús de provetes en forma d'os de gos per avaluar l'amplada mitjana i màxima de fissura (valor real detectat) provocat per esforços de tracció en els elements de tracció R-UHPFRC . És important esmentar que es van fer diferents anàlisis per a cada investigació experimental i es van ac, [EN] All structures, particularly reinforcement concrete structures, apart from meeting necessary security against Ultimate Limit States (ULS), must exhibit appropriate behaviour under service conditions. Generally, the fundamental serviceability requirements that concrete structures should meet are functionality, user comfort and appearance. These requirements cannot, however, be directly checked. Therefore, performance criteria, such as deflection control, vibration control and cracking control, are defined to meet these requirements. Serviceability calculation is complicated because of the cracking phenomenon, the tension stiffening effect, shrinkage, and creep effects. Cracking control in reinforced concrete (RC) structures is generally achieved by limiting stress in steel reinforcement and the concrete matrix. Many concrete code designs specify a maximum steel reinforcement stress after cracking and a maximum crack width for RC or fibre-RC (FRC) structural members, while the design serviceability aspects for Reinforced Ultra-High Performance Fibre-Reinforced Concrete (R-UHPFRC) are poorly considered in UHPFRC codes or recommendations. Many efforts have been made in experimental and theoretical research into the serviceability behaviour of RC or FRC structural elements in the last few decades. However, for R-UHPFRC, knowledge about tension and cracking behaviour must improve and serviceability design requirements have to be further studied. Within this framework, the main purpose of the present PhD thesis is to evaluate the serviceability behaviour of R-UHPFRC. For this purpose, the evaluation of the deformation and cracking behaviour of R-UHPFRC tensile elements is essential. To that end, two main items were addressed and adequately met. The first one was to design an innovative and adequate test methodology to carry out the experiments required for this PhD project. The second involved evaluating the tension stiffening response and cracking behaviour of R-UHPFRC, which are fundamental parameters for R-UHPFRC structures' serviceability design. To study these two parameters, important parameters were considered, such as fibre content, fibre type, size effect, reinforcement ratio and shrinkage effect. In order to evaluate the aforementioned parameters, four experimental campaigns are presented. Each campaign represents a different study level. The first corresponds to the validation of the proposed tensile test methodology and to the examination of the obtained experimental data for future studies required for this PhD project. The second experimental study level corresponds to establishing and undertaking comprehensive experimental programmes with two different steel fibre types and fibre contents. Different cross-section and reinforcement ratios were used to evaluate the size effect and fibre content effect, respectively. The effect of the micro- and macro-steel fibres combination on the deformation and cracking behaviour of tensile R-UHPFRC elements was investigated in a specific experimental study. The third level corresponds to an intensive shrinkage test, which was conducted to obtain the shrinkage value of the UHPFRC used in this PhD study. The final level corresponds to a specific experimental study, done by modifying the specimen's geometry and using the dog bone-shaped specimens to evaluate the average and maximum crack width (real detected value) caused by tensile stresses in R-UHPFRC tensile elements. It is worth mentioning that different analyses were performed for each experimental research and appropriate results were achieved to fulfil the thesis aims. Keywords: cracking behaviour, design criteria, durability, fragility curve, post-cracking tensile stiffness, serviceability behaviour, shrinkage, SLS requirements, structural design, tensile elements, tension stiffening, test method, tie, UHPFRC., This work is part of Project “BIA2016-78460-C3-1-R” supported by the State Research Agency of Spain

Vermiculite materials are widely used as insulation material in the industry, fire protection systems, and fire stoves. The high dimensional stability of vermiculite boards ensures that thermal runways in the insulation lining are avoided. Vermiculite boards for high-temperature applications are produced from thermally expanded vermiculite and alkali silicate binder. Here, we show the impact of potassium silicate binder and vermiculite source on the dimensional stability of vermiculite boards. The vermiculite boards expand at 500–830 °C and shrink stepwise at 1000–1250 °C and 1400 °C, respectively, when heated at 10 °C min−1 in ambient air. The expansion process is discussed in relation to the boards containing non-expanded particles and metal carbonates. The evolved gas analysis indicates that the CO2 release from metal carbonates is the potential cause of the expansion of some vermiculite types. The shrinkage is initiated by the dehydroxylation of the clay structure. The binder promotes crystallisation during the shrinkage, ceasing the shrinkage process at higher temperatures. The expansion and shrinkage of vermiculite boards are anisotropic and depend on the board density and vermiculite origin. These findings provide new insights into the expansion and shrinkage behaviour of vermiculite boards.

Expansion joints on bridges are devices that enable relative displacements of the superstructure spans from the effects of temperature, traffic load and long-term effects. They are placed at the ends of the bridge, where they bridge the space between the superstructure and the abutment, while on very long bridges they are installed at all places where the superstructure breaks between individual sections of the bridge, in order to enable safe and unhindered traffic. They are the “weak points” of the bridge, as their “leakage” can seriously threaten the function of the bridge. In the seismic prone areas, encompassing seismic action in their design and selection is inevitable. This paper will overview the types of expansion joints, design approach in their selection for new bridges and problems that may arise during their replacement in the rehabilitation process of existing bridges. Movements due to traffic load, seismic movements, movements due to long term effects of the deck (creep and shrinkage) and thermal movements will be considered. Based on practical examples, design for either no damage due to seismic action or partially damaged expansion joints for seismic action, will be contemplated.

Online microwave drying process monitoring has been challenging due to the incompatibility of metal components with microwaves. This paper developed a microwave drying system based on online machine vision, which realized real-time extraction and measurement of images, weight, and temperature. An image-processing algorithm was developed to capture material shrinkage characteristics in real time. Constant-temperature microwave drying experiments were conducted, and the artificial neural network (ANN) and extreme learning machine (ELM) were utilized to model and predict the moisture content of materials during the drying process based on the degree of material shrinkage. The results demonstrated that the system and algorithm operated effectively, and ELM provided superior predictive performance and learning efficiency compared to ANN.

Metropolitan decline in southern Europe was documented in few cases, being less intensively investigated than in other regions of the continent. Likely for the first time in recent history, the aftermath of the 2007 recession was a time period associated with economic and demographic decline in Mediterranean Europe. However, the impacts and consequences of the great crisis were occasionally verified and quantified, both in strictly urban contexts and in the surrounding rural areas. By exploiting official statistics, our study delineates sequential stages of demographic growth and decline in a large metropolitan region (Athens, Greece) as a response to economic expansion and stagnation. Having important implications for the extent and spatial direction of metropolitan cycles, the Athens’ case—taken as an example of urban cycles in Mediterranean Europe—indicates a possibly new dimension of urban shrinkage, with spatially varying population growth and decline along a geographical gradient of income and wealth. Heterogeneous dynamics led to a leapfrog urban expansion decoupled from agglomeration and scale, the factors most likely shaping long-term metropolitan expansion in advanced economies. Demographic decline in urban contexts was associated with multidimensional socioeconomic processes resulting in spatially complex demographic outcomes that require appropriate, and possibly more specific, regulation policies. By shedding further light on recession-driven metropolitan decline in advanced economies, the present study contributes to re-thinking short-term development mechanisms and medium-term demographic scenarios in Mediterranean Europe.

Sensors are crucial in the understanding of machines working under high temperatures and high-pressure conditions. Current devices utilize polymeric materials as electrical insulators which pose a challenge in the device’s lifespan. Ceramics, on the other hand, is robust and able to withstand high temperature and pressure. For such applications, a co-fired ceramic device which can provide both electrical conductivity and insulation is beneficial and acts as a superior candidate for sensor devices. In this paper, we propose a novel fabrication technique of complex multi-ceramics structures via 3D printing. This fabrication methodology increases both the geometrical complexity and the device’s shape precision. Structural ceramics (alumina) was employed as the electrical insulator whilst providing mechanical rigidity while a functional ceramic (alumina-doped zinc oxide) was employed as the electrically conductive material. The addition of sintering additives, tailoring the printing pastes’ solid loadings and heat treatment profile resolves multi-materials printing challenges such as shrinkage disparity and densification matching. Through high-temperature co-firing of ceramics (HTCC) technology, dense high quality functional multi-ceramics structures are achieved. The proposed fabrication methodology paves the way for multi-ceramics sensors to be utilized in high temperature and pressure systems in the near future.

Objective: The long-term outcomes after endovascular abdominal aneurysm repair (EVAR) of abdominal aortic aneurysms (AAAs) have been inferior to those after open surgical repair with regard to reinterventions and late mortality. AAA sac remodeling after EVAR has been associated with endoleaks, reinterventions, and mortality. Therefore, knowledge of the predictors of AAA sac remodeling could indirectly give insight into the long-term EVAR outcomes. In the present review, we aimed to provide an overview of the evidence for anatomic predictors of positive and negative AAA sac remodeling after EVAR.Methods: A systematic literature review and analysis were conducted in accordance with the PRISMA (preferred reporting items for systematic reviews and meta-analyses) and Cochrane guidelines. The PubMed and Scopus databases were searched using terms of AAA sac growth, shrinkage, and remodeling. Eligible studies were identified, and only those studies that had included currently used endografts were included.Results: A total of 19 studies that had reported on a total of 27 anatomic parameters of the aortoiliac anatomy were included. Only 4 parameters had been investigated by more than five studies, 7 parameters were investigated by three to five studies, 7 parameters were investigated by two studies, and 9 parameters were investigated by one study. For the presence of neck thrombus, three of four studies had reported similar results, indicating that the presence of neck thrombus might predict for less AAA sac shrinkage. AAA thrombus, the total AAA volume, the flow-lumen volume, aortic calcification, and the number of hostile neck parameters were only investigated by two to three studies. However, these parameters seemed promising for the prediction of sac remodeling. For hostile neck anatomy, neck length, infrarenal neck angulation, and patency of the inferior mesenteric artery, no significant association with any category of AAA sac remodeling was found.Conclusions: The present review demonstrates neck thrombus, AAA thrombus, number of hostile neck parameters, total AAA volume, AAA flow-lumen volume, and aortic calcification as important anatomic features that are likely to play a role in AAA remodeling after endovascular repair and should be further explored using advanced imaging techniques. We also found that strong, consistent evidence regarding the anatomic predictors of AAA sac remodeling after EVAR is lacking. Therefore, further research with large patient groups for a broad range of predictors of AAA sac change after EVAR is needed to complement the current gap in the evidence.

In recent years, most of the studies have shown that the generalized iterated shrinkage thresholdings (GISTs) have become the commonly used first-order optimization algorithms in sparse learning problems. The nonconvex relaxations of the l₀-norm usually achieve better performance than the convex case (e.g., l₁-norm) since the former can achieve a nearly unbiased solver. To increase the calculation efficiency, this work further provides an accelerated GIST version, that is, AGIST, through the extrapolation-based acceleration technique, which can contribute to reduce the number of iterations when solving a family of nonconvex sparse learning problems. Besides, we present the algorithmic analysis, including both local and global convergence guarantees, as well as other intermediate results for the GIST and AGIST, denoted as (A)GIST, by virtue of the Kurdyka-Łojasiewica (KŁ) property and some milder assumptions. Numerical experiments on both synthetic data and real-world databases can demonstrate that the convergence results of objective function accord to the theoretical properties and nonconvex sparse learning methods can achieve superior performance over some convex ones.

A criterion based on solidification microstructure was proposed to precisely predict the hot tearing behavior of cast alloys, which takes into account the effects of both mechanical and nonmechanical factors. This criterion focuses on the events occurring at the grain boundary, which are determined by the thermal contraction, solidification shrinkage, grain growing and liquid feeding. This criterion responds to a series of factors that affect hot tearing, such as alloy composition, mold design, casting process and microstructure. Its credibility has been validated by studying the hot tearing behavior of Mg-Ce alloys. In conformity with the experimental results, this criterion predicted decrease in the number of rods occurring hot tearing with increasing cerium content. A simplified criterion was derived and validated by Mg-Ce (equiaxed grain) and Mg-Al (columnar grain) alloy systems, which is suitable for the case where the eutectic liquid fraction is low and the liquid feeding can be ignored. In addition, a hot tearing index for equiaxed grains was proposed, that is, | d T / d ( f s 1 / 3 ) | near ( f s ) 1 / 3 = 1 , and its prediction results were consistent with the hot tearing susceptibility calculated from the experimental results.

The effect of particle size (50% passing size (D50) of 20 μm, 14 μm and 7 μm) and content (8%, 10% and 12% by mass) of rice husk ash (RHA) on the autogenous shrinkage evolution of high-strength concrete was investigated. RHA samples were selected based on differences in their pore structures, which were investigated by means of nitrogen adsorption isotherms, scanning electron microscopy and absorbency tests. Cement–pozzolan hydration development was studied using isothermal calorimetry. The concretes were subjected to mercury intrusion porosimetry and compressive strength tests. Considering a statistical 22 factorial analysis with a central point, the results showed that D50 and the interaction between D50 and RHA content influenced the autogenous shrinkage at 28 and 100 days. The water absorbed internally by the preserved RHA pore structure (D50 ≈ 20 μm) in the high cement replacement (12% RHA) mixes reduced the final autogenous shrinkage of concrete without a decrease in compressive strength. In addition, the RHA with a more preserved pore structure accelerated the hydration kinetics by heterogeneous nucleation. However, this behaviour did not influence the early autogenous shrinkage results.

Besides strength and elastic modulus properties of concrete, creep and shrinkage are also important in designing structures as they can affect seriously their integrity in the long term. It is shown that design codes internationally, as well as researchers in general, have omitted to consider the influence of aggregate, in particular its stiffness, in the models developed for estimating creep and shrinkage of concrete. This paper shows that the American ACI, Australian AS 3600, European Eurocode 2, Japanese JSCE and B4 models are mostly found to estimate creep coefficient and shrinkage strain of concrete inaccurately, irrespective of the type of aggregate used – natural, recycled or secondary. It is proposed that the stiffness of aggregate can be represented reasonably by its pore structure and in turn, for ease of measurement, by its water absorption. Two empirical models are proposed for estimating creep coefficient and shrinkage strain of concrete covering a wide range of natural, recycled and secondary aggregates alone or in any combination of these, as well as the cement effect and its proportion effect in the form of aggregate/cement ratio.

O presente estudo versa sobre o uso do peeling orgânico intercalado com mescla de intradérmicos x técnicas de sangria para rejuvenescimento, a fim de que se consiga uma eficácia no tratamento de rejuvenescimento em região diversificada por retração tecidual.

Polymer based composites are widely used for treatment, for example as biofilm resistant seals of root canal fillings. Such clinical use, however, fails more frequently than other dental composite restorations, due to stress-related misfits. The reason for this is that the biomaterials used are inserted as viscous masses that may bond to the substrate, yet shrinkage stresses arising during setting of the cross-linking polymer, work against durable adhesion. Here we combine phase contrast enhanced time-lapse radiography (radioscopy), digital image correlation (DIC) and submicrometer resolution phase-contrast enhanced microtomography (PCE-CT), to reveal the spatial and temporal dynamics of composite polymerization and strain evolution. Radioscopy of cavities located in the upper part of human root canals demonstrates how the composite post-gelation "densification" is dominated by viscous flow with quantifiable motion of both particles and entrapped voids. Thereafter, these composites enter a "stress-relaxation" stage and exhibit several structural adaptations, induced by residual shrinkage stresses. Consequently critical alterations to the final biomaterial geometry emerge: (i) entrapped bubbles expand; (ii) microscopic root filling pull-out occurs; (iii) the cavity walls deform inwards, and (iv) occasionally delamination ensues, propagating out from the root canal filling along buried restoration-substrate interfaces. Our findings shed new light on the interactions between confined spaces and biomedical composites that cross-link in situ, highlighting the crucial role of geometry in channeling residual stresses. They further provide new insights into the emergence of structural flaws, calling attention to the need to find new treatment options. STATEMENT OF SIGNIFICANCE: This work quantifies recurring spatial and temporal material redistribution in composites used clinically to fill internal spaces in teeth. This knowledge is important for both promoting biomaterial resistance against potentially pathologic biofilms and for improving structural capacity to endure years of mechanical function. Our study demonstrates the significant role of geometry and the need for improved control over stress raisers to develop better treatment protocols and new space filling materials. The use of high-brilliance X-rays for time-lapse imaging at submicrometer resolution provides dynamic information about the damaging effects of stress relaxation due to polymerization shrinkage.

Taking the red clay from Guilin, China as the object, this paper prepares red clay samples with different initial water contents, extracts the crack parameters from the images on the samples under cyclic drying and wetting through image processing, and analyzes the laws of crack development. In addition, parallel red clay samples were subject to shrinkage tests and direct shear tests under the same cyclic drying and wetting. Based on the test results, the authors discussed the laws of shrinkage deformaiton and strength change for the samples under cyclic drying and wetting, and examined the relationship between cracking, shrinkage properties, and strength detiroation of the red clay. The results show that: (1) With the growing crack rate, the volume shrinkage ratio constantly declined; the area shrinkage ratio was generally decreasing, but the decrement was not obvious in local places (in some places, the area shrinkage ratio even increased); the shrinkage coefficient generally declined, (2) Through the five dry-wet cycles, it was learned that the cohesion and internal friction angle of red clay strength can be quantified using the crack rate. This finding lays the basis for judging soil strength based on crack rate, and solving actual engineering problems with the red clay.

Owing to the influence of the injection molding process, warpage and volume shrinkage are two common quality defects for products manufactured by glass fiber-reinforced plastic (GFRP) injection molding. To minimize these two defects, an extreme learning machine optimized with a genetic algorithm (GA-ELM), multi-objective firefly algorithm (MOFA), and a multi-objective decision-making method (GRA-TOPSIS) were implemented in this study. All of the experiments, based on Latin hypercubic sampling (LHS), were conducted using Moldflow software to obtain the results for warpage and volume shrinkage. The prediction accuracy of the defect-prediction models based on the extreme learning machine (ELM) and GA-ELM algorithms were compared. The results show that the GA-ELM models can better predict the defect values. Finally, MOFA was used to find the Pareto optimal front, and the GRA-TOPSIS method was used to find the optimum solution from the Pareto optimal front. According to the results of the simulation verification, the warpage and volume shrinkage were effectively reduced by 12.25% and 6.11%, respectively, compared with before optimization, which indicates the effectiveness and reliability of the optimization method.

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.

Polyacrylonitrile (PAN)-based materials have been studied for decades as uranium (U(VI)) adsorbents, because the further products of abundant nitrile groups, amidoxime (AO) groups, show great affinity for U(VI) ions. However, excessive amidoximation could cause the shrinkage of PAN fibers, resulting in decreased adsorption performance. Hence, an amino-reinforced amidoxime (ARAO) swelling layer was constructed on the PAN fiber surface (PAN-NH2-AO) by modification of the strongly hydrophilic amino group to prevent shrinkage. The molecular chains in the ARAO swelling layer would be swelled due to the adsorption of a large amount of water. Simultaneously, U(Ⅵ) ions can penetrate into the ARAO swelling layer with water molecules and coordinate with amino or AO groups, leading to increased adsorption performance. PAN-NH2-AO exhibited maximum U(VI) and water adsorption capacities of 492.61 mg·g-1 and 20.32 g·g-1 at 25 ℃ with a swelling ratio of 20.73%, respectively. The adsorption capacity of PAN-NH2-AO was 0.312 mg·g-1 after a 91-day immersion in Yellow Sea, China. The study of the adsorption thermodynamics and kinetics of PAN-NH2-AO showed that the adsorption process was spontaneous homogeneous chemical adsorption. This paper proposes a novel method to obstruct amidoximation induced shrinkage and to maximize the potential application of PAN-based materials.

Direct ink writing (DIW), an extrusion-based additive manufacturing method, has been proposed as a versatile process for preparing ceramics for structural and functional applications. However, controlling the strength of ceramics during processing remains a challenge. In this study, a novel composite binder system consisting of aqueous polyvinylpyrrolidone solution and Al(H2PO4)3 gel was adopted for the DIW of alumina ceramics. Throughout the process, the mechanical performance, dimensional shrinkage, phase compositions and microstructure of samples were evaluated. The results indicate that the composite binder improves green strength by generating hydrogen bonding, which considerably enhances the strength of alumina ceramics under low-temperature sintering due to the reaction between Al(H2PO4)3 gel and nanosized clay particles. This also promotes the high-temperature sintering performance of Al2O3-based ceramics. Overall, the current composite binder is anticipated to be promising for DIW of alumina ceramics, providing sufficient strength for post-processing and greatly improving strength after low-temperature sintering.

Vat photopolymerization is a versatile 3D printing method that produces parts using polymeric materials with uniform mechanical properties, high quality surface finish and high-resolution features. However, it is challenging to make composite materials with vat photopolymerization mainly due to the imperfect filler dispersion in the photo resin. Herein, we describe a methodology to incorporate aramid nanofibers (ANFs) into a 3D printable photoresin as a dispersion, followed by a solvent exchange process that limits anisotropic shrinkage and cracking of the printed polymer. By incorporating 0.60 wt.% of ANFs, both the tensile strength and toughness increased by 264 % and 219 % respectively, while the Young’s modulus had a 406 % increase compared to the control photoresin.

Low-illumination image restoration has been widely used in many fields. Aiming at the problem of low resolution and noise amplification in low light environment, this paper applies style transfer of CycleGAN(Cycle-Consistent Generative Adversarial Networks) to low illumination image enhancement. In the design network structure, different convolution kernels are used to extract the features from three paths, and the deep residual shrinkage network is designed to suppress the noise after convolution. The color deviation of the image can be resolved by the identity loss of CycleGAN. In the discriminator, different convolution kernels are used to extract image features from two paths. Compared with the training and testing results of Deep-Retinex network, GLAD network, KinD and other network methods on LOL-dataset and Brightening dataset, CycleGAN based on multi-scale depth residuals contraction proposed in this experiment on LOL-dataset results image quality evaluation indicators PSNR = 24.62, NIQE = 4.9856, SSIM = 0.8628, PSNR = 27.85, NIQE = 4.7652, SSIM = 0.8753. From the visual effect and objective index, it is proved that CycleGAN based on multi-scale depth residual shrinkage has excellent performance in low illumination enhancement, detail recovery and denoising.

Near-neutral salt activated slag cement has better performance in environmental protection and shrinkage behavior than common sodium silicate -activated slag (AAS) cement. However, the growth of mechanical performance is too slow, which limits its application. Reactive MgO can improve early mechanical properties, while it may have different effects on the shrinkage due to changes in alkali-activators. Two near-neutral salts, sodium carbonate (SC) and sodium sulfate (SS), were selected to prepare AAS cement. The influence of reactive MgO on autogenous and drying shrinkages was studied. The hydration process and pore structure were assessed with hydration heat and nitrogen adsorption, respectively. The phase composition was evaluated by thermogravimetry (TG/DTG) and X-ray diffraction (XRD). The results indicate that the addition of reactive MgO increases the autogenous shrinkage of SC and SS activated slag. This is mainly due to accelerated reaction by reactive MgO. The drying shrinkage of AAS mortars activated with SC increases first and then decreases with the increase in reactive MgO. For SS activated slag, the more the reactive MgO used, the lower the drying shrinkage is observed. This is related to the effect of reactive MgO on pore structure and hydration products. When reactive MgO increases from 2% to 10%, the mesopore in SC activated slag increases at first and then decreases, while the SS activated slag group shows a constant decrease. Reactive MgO promotes the formation of hydrotalcite in SC activated slag, while AFt is found in SS activated slag. Hydrotalcite and AFt are crystalline products, which are beneficial to inhibit drying shrinkage.