Compressed Thickness Research Articles

Compressive behavior of manufactured sand recycled coarse aggregate concrete-filled steel tubular short columns

To study the mechanical properties of manufactured sand recycled aggregate concrete-filled steel tubular (RACFST) columns, a total of 81 square short RACFST column specimens with different types of manufactured sand and natural sand were created and subjected to axial compression tests. The variables included sand type, core concrete strength, slenderness ratio, and steel tube thickness. The failure mode, axial load-displacement curve, axial compressive capacity, and deformation capacity of the specimens were analyzed in detail. The results indicate that the failure mode of the specimen is generally waist drum-type failure and shear-type failure, and both of them are local buckling. The load-displacement curve of the manufactured sand specimen is similar to that of the natural sand specimen, but the steel tube of the manufactured sand specimen yields later than that of the natural sand specimen. Generally, the limestone manufactured sand specimen has the highest axial compressive capacity and the best ductility ratio, while the pebble manufactured sand specimen has an axial compressive capacity similar to the natural sand specimen but a lower ductility ratio. The effects of concrete compressive strength, slenderness ratio, and steel tube thickness on specimens with manufactured sand are similar to those with natural sand. Based on the results of this experimental study, a formula for calculating the axial compressive capacity of square RACFST columns is provided.

Numerical investigation on composite enclosure walls of RC frames infilled with autoclaved aerated concrete panels under cyclic loads

To promote the application of prefabricated walls and autoclaved aerated concrete (AAC) panels in the Metro industry, the seismic resistance investigations on composite enclosure walls (CEWs) of reinforced concrete (RC) frames infilled with AAC panels suitable for the Metro station were performed. Based on the field test arrangement, the corresponding finite element (FE) models were established and verified according to the experimental results. Moreover, the parametric studies, including with or without AAC infill panels, the compressive strength and thickness of the AAC panels, the compressive strength of frame concrete, and the door opening location and width, were further investigated to explore the structural behavior under cycle loads. The results indicate the seismic performance of CEWs can be effectively improved by infilling AAC panels. The increase in the strength and thickness of AAC panels could enhance the load-bearing capacity and ductility of CEWs. The structural stiffness and cumulative energy dissipation of CEWs are increased with the increasing thickness of AAC panels. The increased range of the peak load, ductility, initial stiffness, and cumulative energy dissipation of CEWs would be maintained within 20.5 % when the concrete strength of the RC frame increases from 35 MPa to 45 MPa. With increasing distance between the constructional column and the door opening, the load-bearing capacity of CEWs is significantly decreased, while the ductility is enhanced. The high initial stiffness could be obtained when the door opens near the constructional column. The load-bearing capacity and initial stiffness of CEWs would be decreased with increasing width of the door opening, while the insignificant effect of the changed door opening width on the ductility.

The effects of brick wall and RC tie variables on the seismic performance of low-rise confined masonry buildings

An extensive parametric investigation is carried out to determine the effects of different RC tie system and brick wall variables on the performance of confined masonry walls and buildings. The variables considered include: the number of storeys and adjacent walls, the walls aspect ratio, thickness and compressive strength of masonry walls, presence of openings, the RC tie system dimensions, compressive strength and detailing of the longitudinal and transverse reinforcements. The main aim of the investigation is to verify the efficiency of some of the prescriptive code recommendations and to provide a basis for further descriptive guidelines for low-rise confined masonry buildings. Among the major conclusions, it is found that the main affecting parameters are those of the masonry walls themselves. When the walls have sufficient shear capacities, due to lower aspect ratio, higher compressive strength and wall thickness and lack of, or small openings, the flexural demand on the tie system is small and its elements act mainly as axially-loaded tie elements. Therefore, the least affecting parameters are those of the tie system's reinforcement detailing. However, when the masonry walls are weak in shear (low masonry strength and large openings), the demand on the tie system increases, to the point that instead of acting as an integral part of the wall, it acts similar to a weak, moment-resisting frame having infill masonry walls, for which it has not been designed. The scenarios that this will happen include: the wall aspect ratios AR > 2, the masonry compressive strength, f′m < 5.0 MPa and the ratio of length of opening to the length of the wall, Ol/Wl > 0.5. To avoid such behaviour, it is also suggested that the tensile stresses in the longitudinal bars of the RC tie elements be limited to 0.6fy.

Hygroscopic behavior of thermo-hygro-mechanical (THM) densified oil palm sawn timber

ABSTRACT To facilitate the drying process and enhance the properties of oil palm wood, oil palm boards were mechanically pre-dewatered and thermo-hygro-mechanically (THM) densified. The thickness of the boards was reduced with compression ratios of 40%, 60% and 75%. Since densified wood tends to recover from compression, especially under humid conditions, this study examined the set-recovery and the hygroscopic behavior of THM densified oil palm wood. The equilibrium moisture content (EMC), differential swelling and swelling coefficient, linear swelling and shrinkage as well as the differential swelling anisotropy were determined under climate conditions with different relative humidity (RH) (20°C/35% RH, 20°C/65% RH and 20°C/85% RH). The maximum swelling was measured after water soaking and the remaining set-recovery was evaluated after re-drying at 103°C. The EMC was reduced by the THM process by around 20%. In the direction of compression (thickness), the densified specimens show higher values for all analyzed swelling and shrinkage parameters than the undensified specimens from the equivalent position within the trunk. The maximum swelling in thickness of 22–38% during water soaking is mostly reversed by shrinkage during re-drying and a comparably low remaining set-recovery of 3–8% is measured at oven dry condition.

Experimental investigations on the partially concrete-filled steel tubular slender beams

This paper focuses on the flexural behaviour of partially concrete-filled steel tubular (PCFST) beams having slender cross-sections (D/t > 150). PCFST beam is developed by optimising the tension zone concrete in a concrete-filled steel tubular (CFST) beam. Twelve specimens were investigated under a four-point load to understand the flexural behaviour and load transfer mechanism of PCFST slender beams. Parameters considered for the tests are concrete compressive strength, shear-span-to-depth ratio, and concrete wall thickness. The failure mode, load-deflection, strain distribution and moment-rotation data of the test specimens are reported and compared. In general, PCFST beams exhibit the same flexure behaviour as CFST beams in terms of flexural resistance and stiffness, and the weight reduction is around 40 %. However, composite action is lost in PCFST without tension zone concrete, and the beam behaves like an empty steel tube. Therefore, a minimum concrete wall thickness (tc,min) in the tension zone is required in PCFST and an equation for tc,min is proposed based on the test results. Concrete compressive strength is found to have lesser significance in the PCFST beam, whereas a decrease in the shear span-to-depth ratio from 2 to 1 can alter the mode of failure from flexure to shear. A numerical model is developed using ABAQUS to support the test results. This study finds the PCFST beam an optimised replacement for CFST beams in flexure-predominant structural systems. Additionally, a flexure capacity equation is proposed using the plastic stress distribution method, and made good predictions with the experimental and finite element results.

Surface Subsidence Characteristics and Causes Analysis in Ningbo Plain by Sentinel-1A TS-InSAR

In recent years, the Ningbo Plain has experienced significant surface subsidence due to urbanization and industrialization, combined with the area’s unique geological and hydrological conditions. To study the surface subsidence and its causes in the Ningbo Plain, this study analyzed 166 scenes of Sentinel-1A SAR images between January 2018 and June 2023. The time series interferometric synthetic aperture radar (TS-InSAR) technique was used to acquire surface subsidence information in the area. The causes of subsidence were analyzed. The results show that: (1) the annual deformation rate of the Ningbo Plain ranges from −44 mm/yr to 12 mm/yr between 2018 and 2023. A total of 15 major subsidence zones were identified by using both the subsidence rate map and optical imagery. The most severe subsidence occurred in the northern industrial park of Cixi City, with a maximum subsidence rate of −37 mm/yr. The study reveals that the subsidence issue in the main urban area has been significantly improved compared to the 2017 subsidence data from the Ningbo Bureau of Natural Resources and Planning. However, three new subsidence areas have emerged in the main urban area, located, respectively, in Gaoqiao Town, Lishe Town, and Qiuyi Village, with maximum rates of −29 mm/year, −24 mm/year, and −23 mm/year, respectively. (2) The causes of subsidence were analyzed using various data, including land use data, geological data, groundwater-monitoring data, and transportation network data. It is found that a strong link exists between changes in groundwater levels, compressible layer thickness, and surface subsidence. The groundwater levels changes and the soft soil layer thickness are the main natural factors causing subsidence in the Ningbo Plain. Additionally, the interaction between static loads from large-scale industrial production and urban construction, along with the dynamic loads from transportation networks, contribute significantly to surface subsidence in the Ningbo Plain. The results from this study enhance the understanding of the driving factors of subsidence in the Ningbo Plain, which can provide necessary guidance for the economic development and decision-making in the region, helping to manage and potentially mitigate future subsidence issues.

Numerical studies of the distribution capability of a continuous linear strain soil base model for largesized raft foundations

The paper examines the existing methodology for determining the main design parameters of the model in the form of a continuous linearly strained layer of finite distribution capability (the design thickness of the layer H0 and design stress-strain modulus E0) to simulate the adequate interaction between soil bases and large-size slab foundations. The aim of this work is to numerically study the stress-strain state of a uniformly loaded flexible rectangular foundation slab when the thickness of the soil base model layer is reduced in the form of a continuous linearly deformed layer of finite distribution capacity. Numerical studies of the effect of the thickness of the layer of the specified soil base model that interacts with a large-size flexible slab foundation of various rectangular shapes in plan were conducted in the SCAD package using the finite element method. The numerical study results have shown that when the ratio H0/Ha (the design thickness of the layer of the soil base model H0 to the actual compressible thickness of the soil base Ha) decreases, the maximum moment forces along the orthogonal axes of rectangular foundations decrease to 50% because of the decrease in the distribution capability of the soil base model and, accordingly, in the edge reactions R under the slab at equal average settlements of the slab saver. Numerical studies have shown interesting results on the distribution of moment forces in flexible rectangular slabs, where the maximum is outside the center of gravity of a uniformly loaded raft, which confirms the peculiarity of the interaction of flexible slabs with relatively narrow compressible layers under the sole. With an appropriate in-situ experimental justification, the use of the soil base model in the form as a continuous linearly strained layer of finite distribution capability with the design parameters (H0 and E0) rather than with the actual parameters (Ha and Ea) in calculations of large-size slab foundations can be of fundamental practical importance in their rational design, as the reinforcement can be reduced to 50%

NUMERICAL STUDIES OF THE DISTRIBUTION CAPACITY AND DEFORMABILITY OF THE SPATIAL MODEL OF THE SOIL BASE IN THE FORM OF A LINEAR-DEFORMED LAYER

The article analyses the existing approaches to modelling the interaction between a structure and a soil foundation, which consider the joint deformation of the soil and the structure. The “base-foundation-structure” models can be created in one-dimensional, two-dimensional, or three-dimensional space. Each of these models has its own set of boundary conditions and calculation methodology The advantages and disadvantages of each model, during application in engineering calculations, are presented. The purpose of research is to substantiate the methodology for assigning the geometric parameters of a three-dimensional model of a soil foundation, represented as a linearly deformed layer of finite resolution, for adequate modelling of interaction in the "base- foundation-structure" system. A finite-element model of the interaction between the soil base and the slab foundation was built using the modern SCAD software package. The modelling was performed in three dimensions. The soil base is represented by volumetric finite elements with constant deformation characteristics. The foundation is modelled by plate finite elements In context of this research, the slab model of the foundation was assumed to be rigid to neglect stress redistribution in the above-ground part of the building. Based on the analysis of modern approaches to the assignment of geometric parameters to the model of the soil base represented by a continuous linearly deformed layer with finite overall dimensions, which is created in a three-dimensional problem statement, it was shown that today there is no single approach to modelling such a “base-foundation-structure” system. Numerical studies of the effect of rigid horizontal constraints in the plan on the stress-strain state of a uniformly loaded rigid foundation interacting with a linearly deformed layer (compressible thickness) of finite distribution capacity were carried out using the SCAD program. Based on the analysis of the results of numerical calculations for a three-dimensional problem, the minimum allowable sizes in terms of the model of a linearly deformed layer of finite distribution capacity, which considers the distribution of compressive stresses along the depth at an angle of α = 25º to the vertical from the edges of the loaded foundation, are substantiated. At the same time, the overall size of the model in the plan according to the distribution angle α = 25º has practically no effect on the average settlement and maximum moment forces of the foundation compared to the angle α = 45º. Keywords: slab foundation, soil foundation, linear-deformed model, distribution angle, stress-strain state.

Frictional slippage of elastomeric disks compressed between rigid platens and subjected to torsion

A new analysis is applied to compressible, linearly elastic disks that are compressed by flat rigid platens. The disks are not bonded to the platens and Coulomb (Amonton) friction is assumed to act at the interfaces between the disk and the platens. Slip may occur in an outer annular region, while the inner circular (stick) region of the disk does not slip. The critical radius (slip boundary) is of major interest. The governing equilibrium equations in terms of the deflections are satisfied exactly. Approximations are made in some of the boundary conditions and the transition (matching) conditions at the critical radius. Numerical results are presented for nearly incompressible disks, both for (a) compression only and (b) compression plus torsion. In the latter case, during twisting, either the compressed thickness of the disk is fixed while the compressive force varies, or the compressive force is fixed while the thickness varies. The effects of the aspect ratio and Poisson's ratio of the disk, the coefficient of friction at the platens, and the twist angle on the critical radius, stresses, compressive force, torque, and effective compression and shear moduli are investigated. Applications include structural (especially bridge) bearings, seismic-isolation devices, mounting blocks and bushings, and rheometry.

A numerical study on a novel demountable cold-formed steel composite beam with profiled steel sheeting

Cold-formed steel composite beams are known for their unique advantages, like being lightweight and ease of installation. The use of profiled steel sheeting in cold-formed composite beams reduces construction time and costs by acting as a permanent formwork in the composite beams. The current study presents a 3D finite element model of cold-formed steel composite beam specimens comprising a cold-formed double-lipped channel section, profiled steel sheeting, concrete slab, and bolted shear connector. Employing bolted shear connectors, structural components can be deconstructed and replaced after their service life expires or if they are damaged. The characteristics of the materials obtained from an experimental program were assigned to the finite element model. Geometric characteristics, material nonlinearities, and loading procedures were attentively simulated, and a dynamic explicit procedure was employed for the numerical analyses. A comparison of the results obtained from the finite element models and the available experimental results validated the precision of the models. Then, numerical studies were conducted to investigate the effects of various parameters, including compressive strength of concrete, thickness of concrete slab, height and grade of cold-formed steel section, thickness of profiled steel sheeting, number and diameter of shear connectors, on the behavior of the composite beam. The results showed that the height and grade of the cold-formed steel section and compressive strength and thickness of the concrete slab have a significant effect on increasing the capacity of the composite beam.

Integrating SBAS-InSAR and Random Forest for Identifying and Controlling Land Subsidence and Uplift in a Multi-Layered Porous System of North China Plain

Controlling groundwater table decline could mitigate land subsidence and induced environmental hazards in over-explored areas. Nevertheless, this becomes a challenge in the multi-layered porous system as (in)elastic deformation simultaneously occurs due to vast spatiotemporal variability in the groundwater table. In this study, SBAS-InSAR was used to estimate annual land deformation during 2017–2022 in a specific region of North China Plain, in which aquifers are composed of many layers of fine-grained compressible sediments and the groundwater table has experienced a prolonged decline. The random forest (RF) was applied to establish the nonlinear relationship between accumulated deformation and its potential driving factors, including the depth to the groundwater table (GWD) and its change rate, and the compressible sediment thickness. Results show that the marked subsidence and uplift co-exist in the region even though the groundwater table has risen widely since the South–North Water Diversion Project. The land subsidence is attributed to inelastic compaction of the thick compressible deposits in depression cone centers, where the GWD is over 40 m and 90 m in the shallow and deep aquifers, respectively. In contrast, the marked uplift is primarily attributed to fast rising of the groundwater table (e.g., −2.44 m/a). The RF predictions suggest that, to control the subsidence, the GWD should be less than 20 and 70 m in the shallow and deep aquifers, respectively, and the rising rate of the GWD should increase to 2–5 times of current rates in the depression cones. To mitigate the marked uplift, the rising rate of the GWD should reduce to 1/2–1/5 of the current rates in the shallow aquifers. The uneven deformations of sediments in the depression cone centers and uplift in their boundaries may exacerbate geohazards. Therefore, it is vital to implement appropriate governance of groundwater recovery in the multi-layered porous system.

A numerical analysis of the effect of layer-scale and microscopic parameters of membrane electrode assembly in proton exchange fuel cells under two-phase conditions

A multiphysics, multiphase, multiscale model of the membrane electrode assembly (MEA) of a polymer electrolyte membrane fuel cell (PEMFC) is presented. The model accounts for varying local effective transport that arise from assembly compression of the gas diffusion layer (GDL) and MEA microstructure, providing a more realistic description of heterogeneities. The model is validated against previous experimental data in terms of polarization curve, effect of inlet relative humidity on performance, and rib/channel saturation distribution. Then, a parametric analysis of layer-scale (compression and GDL thickness) and microscopic (pore radius and defect volume fraction) parameters is presented. The results show that performance can be improved by reducing compression under the rib (provided that electrical contact resistances are negligible), tailoring GDL thickness at intermediate values around 200μm, designing macroporous layer (MPL) and catalyst layer (CL) with pore sizes between 50–100nm and 0.5–1μm, respectively, and reducing large defect volume fractions in MPLs and CLs. To achieve these goals, an integral design of MEAs is necessary to minimize electrical contact resistances, cracks and defects, reduce inhomogeneous compression and produce highly porous multiscale structures with large continuum pore sizes at multiple scales.

Estudio comparativo de la dosis de radiación de la mamografía espectral con contraste (CEM), mamografía digital y tomosíntesis mamaria

IntroductionThe use of contrast-enhanced spectral mammography (CESM) has increased in recent years, as has awareness of radiation dose safety among professionals and patients. The principal aim of this study was to compare radiation exposure measured using the entrance surface dose (ESD) and the average glandular dose (AGD) in CESM, full-field digital mammography (FFDM) and digital breast tomosynthesis (DBT). Our second objective was to evaluate differences caused by compressed breast thickness, compression force and patient age. Material and methodsA retrospective observational study included all patients who had undergone a CESM between May 2021 and May 2022. Data was collected on ESD and AGD from the different CESM studies, and breast density and volume were determined by 2expert radiologists. The comparative analysis focused on the dose of radiation received during the craniocaudal (CC) projection of the right breast in CESM studies and FFDM or DBT, performed within a 12-month period. Lastly, a statistical analysis was performed to determine the influence of breast compression thickness, compression force and patient age. ResultsSeventy-seven patients participated in the comparative study and forty-four in the dosimetric study. Differences in radiation dose (ESD/AGD) were found among the 3breast imaging techniques. The dose in CESM (1.70/5.39 mGy) was lower than in DBT (2.19/6.79 mGy) and higher than in FFDM (1.26/4.06 mGy) for an average breast compression thickness of 59.64mm. A positive correlation was observed between the dose received in CESM and breast compression thickness (ρ=0.55), and a negative correlation was observed with patient age (ρ= –0.27). No differences in dosimetric variables were observed for different compression forces. ConclusionsThe ESD and AGD in the CC projection of the right breast in CESM are higher than in FFDM but lower than in DBT. The dose had a positive correlation with breast compression thickness and a negative correlation with patient age.

Structural optimization study on porous transport layers of sintered titanium for polymer electrolyte membrane electrolyzers

An effective way to improve the performance of polymer electrolyte membrane (PEM) electrolyzers is to optimize the structural design of porous transport layers. This paper uses mirco-computed tomography (μ-CT) to study the three-dimensional microstructure distribution characteristics of commercial sintered titanium powder-based porous transport layers (PTL). A three-dimensional PTLs model with different porosity, pore diameter and thickness was established by Stochastic reconstruction model method. In addition, lattice Boltzmann method is used to study the influence of PTL structural parameters and single-phase permeability. The results show that the large compression thickness not only can significantly improve the PTL single-phase permeability, but also has little effect on the interface contact area. In addition, an increase in pore size and porosity will increase the transport performance while reducing interface contact. It is recommended that the average pore size of PTL should be greater than 10 μm, and the porosity should be greater than 30%. This work can be used to guide the preparation technology of PTL in order to improve the performance of PEM electrolyzer.

Nonlinear deformations of the compacted soil base under the broadening of piles in punched holes

The peculiarity of piles in punched holes with broadening (PPH), performed according to the technology of foundations in rammed pits, is considered to be a high load-bearing capacity compared to traditional driven piles. At the same time, from the long-term practice of using the PPH, the actual excess of the calculated settlement is noted. This is due to a significant excess of pressure of the order of 1,000-3,000 kPa under the widening of the pile over the calculated resistance of the compacted soil layer. This makes it necessary to calculate such a foundation for the second group of limit states, taking into account the nonlinearity within the limits of the calculated allowable pressure. The article compares three methods of calculating settlement taking into account non-linearity: according to the tables of the standard, the methods of N.V. Ornatsky and M.V. Malyshev. It is noted that the methods do not always correspond to the actual work of the foundation in the ground, which can reduce the reliability of calculations. The authors proposed to modernize the existing methods of calculating settlement due to the peculiarities of the work of the PPH. In the calculation scheme of the PPH, to determine the settlement, it is necessary to take into account the soil layer with an increased modulus of deformation created during the punching of the well and the formation of broadening. Zones of marginal equilibrium develop with a margin within the boundaries of the compacted layer under broadening. It is proposed to take into account the nonlinear dependence of soil deformations on stresses within the specified boundaries, and to take into account the remaining deformations of the compressible thickness in a linear formulation. Taking into account the non-linearity in the determination of settlement leads to an increase in the reliability of the application of the piles in question, especially in weak clay water-saturated soils, and in relatively strong soils allows us to confirm the reliable use of PPH.

Physicomechanical Characterization of a Novel Resin-Modified Glass Ionomer Luting Cement Functionalized with a Phosphate Functional Monomer

Background. Resin-modified glass ionomer cements (RMGICs) are characterized by their ability to chemically bond with the tooth structure and their fluoride release, making them commonly used to retain indirect restorations. However, inferior mechanical properties and solubility (SO) are their main drawbacks compared to the most recent resin-based cement. Aim of the Study. Formulate a novel brand of experimental RMGIC (eRMGIC), based on RMGIC by incorporating 2-(methacryloxy) ethyl phosphate (2-MEP), an organophosphorus monomer with the potential to enhance mechanical properties along with low SO. Materials and Methods. eRMGICs were prepared by the inclusion of 2-MEP monomer with different weight percentages (0–40 wt%) into the RMGIC’s liquid (Fuji PLUS, GC. Corp.), then their compressive strength (CS), flexural strength (FS), film thickness (FT), setting time (ST), SO, and water sorption were examined and compared to the conventional RMGIC. Furthermore, a scanning electron microscope analyzed their surface homogeneity and integrity. Shapiro–Wilk test of normality was used to analyze data, one-way analysis of variance, Dunnett T3, and Tukey’s honest significant difference post-hoc tests. Results. After 28 days and 180 days of storage, the values of CS of the eRMGICs were significantly higher. However, after 24 hr of storage, the values were comparable to the control group. The FS results showed a double-fold increase in different concentrations of eRMGICs through all the time intervals ( p &lt; 0.001 ) compared to conventional RMGIC. Furthermore, the inclusion of 2-MEP increased water uptake and decreased SO. The FT of experimental eRMGICs cement showed a statistically significant increase with increasing 2-MEP concentration. However, it was within the specification given by ISO 9917-1:2007. There was a decrease in the ST of eRMGICs compared to control cement; however, it was within the specification given by ISO 9917-2:2017. Conclusions. 2-MEP monomer showed encouraging results and could be used in producing new (eRMGICs) with enhanced physicomechanical properties, which can increase the longevity of cement and improve its ability to resist occlusal stresses without fracture.

3D phantom for image quality assessment of mammography systems

Objective. To present an innovative approach for the design of a 3D mammographic phantom for medical equipment quality assessment, estimation of the glandular tissue percentage in the patient’s breast, and emulation of microcalcification (μC) breast lesions. Approach. Contrast-to noise ratio (CNR) measurements, as well as spatial resolution and intensity-to-glandularity calibrations under mammography conditions were performed to assess the effectiveness of the phantom. CNR measurements were applied to different groups of calcium hydroxyapatite (HA) and aluminum oxide (AO) μCs ranging from 200 to 600 μm. Spatial resolution was characterized using an aluminum plate contained in the phantom and standard linear figures of merit, such as the line spread function and modulation transfer function (MTF). The intensity-to-glandularity calibration was developed using an x-ray attenuation matrix within the phantom to estimate the glandular tissue percentage in a breast with a compressed thickness of 4 cm. Main results. For the prototype studied, the minimum confidence level for detecting HA μCs is 95.4%, while for AO μCs is above 68.3%. It was also possible to determine that the MTF of the commercial mammography machine used for this study at the Nyquist frequency is 41%. Additionally, a one-to-one intensity-to-glandularity calibration was obtained and verified with Monte-Carlo simulation results. Significance. The phantom provides traditional arrangements presented in accreditation phantoms, which makes it competitive with available devices, but excelling in regarding affordability, modularity, and inlays distribution. Moreover, its design allows to be positioned in close proximity to the patient's breast during a medical screening for a simultaneous x-ray imaging, such that the features of the phantom can be used as reference values to specify characteristics of the real breast tissue, such as proportion of glandular/adipose composition and/or μC type and size lesions.

Stress-Strain State Assessment of Building Subfoundations Having Flexible Constructive Scheme in Irregular Soil Stratification

Introduction. One of the main problems in the operation of buildings and structures is possibility of their damage due to non-uniform deformation of subfoundation soil caused by the various natural and technogenic factors. To establish the possible character and degree of damage of the above-surface structures, it is necessary to calculate the value of subfoun- dation relative differential settlement at the level beneath the foundation bottom. The subfoundation settlement is calculated within the compressible soil thickness using the specific gravity values and soil deformation modulus. The increment of settlement is induced by the increase of vertical stresses in the massif and increase of soil deformability upon growth of moisture. The purpose of the study is to establish the dependence of the magnitude of the relative difference in settlement on the deformation properties of soils with uneven occurrence of layers in order to predict the nature of damage to above-ground structures.Materials and Methods. An example of subfoundation deformation calculations at the bottom level of the free-standing foundations of a building having flexible constructive scheme has been studied. A model of stratification of two heterogeneous geotechnical elements with a 1:4 boundary slope and differing physical and mechanical properties has been used. It has been assumed that one of the geotechnical elements has natural properties enabling the building foundations to rest on it without prior site preparation. Another geotechnical element has significantly worse properties. The calculations on determining the settlement have been made in accordance with the layer-wise summation methodology.Results. The regularity in alteration of the predicted settlement value depending on the ratio of firm and soft soils thickness in the irregular stratification has been established. It has been proven that the difference between the specific gravity values of the heterogeneous beds within 10 % does not affect the depth of compressible soil thickness if the calculation of settlement is made using the layer-wise summation methodology.Discussion and conclusions. The calculation results analysis of the subfoundation settlement of the equidistant column foundations was carried out, the engineering solution was proposed to ensure reliability per limit state groups.

Evaluation of the relationship between digital mammography radiation dose and patient age, breast volume and density

Aims: To determine the average radiation dose values in patients who underwent routine screening mammography in our hospital, establish the relationship between breast density and volume, and investigate other factors affecting radiation dose.&#x0D; Methods: Screening bilateral mammography was retrospectively evaluated within the specified period of 2 months. Patient age, breast density ratio, mammographic size of the breast, calculated breast volume, tube voltage, current, exposure time (ms), compression force (kg), compression thickness (mm), and radiation dose (mGy) given in each projection were recorded separately for each patient. According to the BI-RADS, breast densities classified as types A-B were considered non-dense, while types C-D were considered dense breasts. The 75th percentile dose value (mGy) was chosen as the cutoff for high dose group. Logistic regression analyses were used to examine the factors affecting radiation dose.&#x0D; Results: 1720 mammograms from 430 patients were studied. 276 (64.2%) breasts were non-dense, while 154 (35.8%) breasts were dense. The mean total breast volume was 595±334 ml, compression thickness was 36.5±12.0 mm, and radiation dose was 2.04±0.75 mGy. There was a negative correlation between radiation dose and age (r=-0.330, p

Size, but not sex, predicts pinch force and exoskeleton mechanical properties in crayfish of the genus Faxonius

AbstractStudies of animal weaponry and defensive structures rarely take into consideration their underlying mechanical properties. We measured the compressive strength and thickness of the exoskeleton of the claw (chela) in two North American crayfish species, Faxonius virilis and F. limosus. We performed similar measures on the carapace, a body region not directly involved in agonistic contests. Males of both species generated significantly stronger maximum pinch forces than females. However, these differences can be attributed to differences in claw size between the sexes. The thickness (ultrastructure) of the claw exoskeleton was a significant predictor of its compressive strength and likely explained the difference in compressive strength we observed between the two species. Neither claw thickness nor claw compressive strength was correlated with maximum pinch force. Additionally, we found that crayfish body size was a strong predictor of carapace compressive strength and thickness, whereas sex was not. The claw had greater compressive strength and thickness than the corresponding values for the carapace. Our study shows that the mechanical properties of the crayfish exoskeleton are largely a function of size and highlights the need to integrate mechanical properties into studies of animal morphology and performance.