measurements for quality control, diffusion experiments and spin diffusion. The devices used are varying from low-field mobile NMR to high field laboratory spectrometers.
There is a multitude of techniques today every one of them with advantages and disadvantages. We can choose between them taking into account numerous variables, like the amount information extracted, cost, speed, benefits, complexity of the method, and comparison with other methods which can by applied to the specific problem. The unique feature of NMR is the non-destructive approach, making this method a suitable technique for measuring works of art or for complex in vivo experiments. The investigation of materialproperties is one of the most important goals of NMR. The mobile sensors developed lately make measurements possible at remote locations for some historical buildings or measuring rocks at the drilling platform minutes after the extraction. In some particular fields of investigation like amorphous samples or biomolecules, we can get structural information only from NMR measurements. After about 60 years of research in this domain, the technique is one of the most versatile and reliable method in use.
Innovative hybrid forming processes demand for new methods and implementations of FE models to accurately simulate and optimize them. One application is the interrelationship of strain and damage to materialproperties like the local electrical resistivity. To investigate the necessity of implementing such interrelationships, a conventional solid forward extrusion process was modelled and later extended with DC resistance heating. This included a strong coupling between plastic strain and local resistivity of the steel that was used. Experiments do not show significant changes in the punch force for various processing conditions. This behaviour is reproduced by the presented model. At the same time, the simulations of resistively heated samples show different local temperatures at the end of the process for the coupled and uncoupled approach. For high electric currents, significant differences in the temperature distribution between constant and strain dependent materialproperties could be predicted.
The results from the retinotopically defined masks as well as those from the searchlight approach suggest that there is a lot of information about materialproperties in early visual areas. As the results from the image statistics classification analysis show, very simple image statistics, in particular luminance and spatial frequency information, as well as the filter parameters defined by Portilla and Simoncelli, can be quite informative about certain types of materialproperties. The involvement of these could be the driving force for the classifier results in early visual areas. This notion is confirmed by the comparison of the labels assigned by the images statistics classifier and the MVPA. The effects of this analysis seem to be moderate, which is, however, expected, taking into account the noisiness of fMRI data and the fact that each material image was seen only once by each participant. All together, our results argue for an involvement of low-level image statistics in material perception. This agrees well Hiramatsu et al. (2011) , who found highest accuracies in V1 and V2 for classification of material categories. The few studies that have examined the neural basis of surface/material perception have found that tasks associated with visual material perception lead to an increase in activation in medial regions of the ventral extrastriate cortex, especially the collateral sulcus and parahippocampal gyrus ( Newman et al., 2005 ; Cant and Goodale, 2007, 2011 ;
The materialproperties of aluminum are assumed to be isotropic and constant, with a Young's modulus of ܧ ௨ ൌ ǡͳ ή ͳͲ ଵ Pa and a Poisson's ratio of ߥ ௨ ൌ Ͳǡ͵͵. Furthermore, the density is
ߩ ௨ ൌ ʹͲͲ kg/m³ and the structural damping coefficient is chosen to be ߟ ௨ ൌ ͲǡͲͲͷ. For the core
layer, the materialproperties of a particular viscoelastic material are applied. The material is a dedicated mixture of bromobutyl rubber for aeronautic applications as vibration dampers, developed in cooperation with the German Institute of Rubber Technology (Deutsches Institut für Kautschuktechnologie e.V.). The materialproperties are significantly frequency and temperature dependent and can be characterized by twelve parameter sets of the generalized Maxwell model, as well as by WLF and Arrhenius shifts. In Figure 4, the contour curves of the shear storage modulus and loss factor of bromobutyl rubber are presented.
According to different amounts and arrangements of teeth, seven basic types of radular morphologies have been recognized (e.g. Gray, 1853; Hyman, 1967; Steneck and Watling, 1982). In addition, radulae can show different tooth morphologies between taxa, but with a similar universal structure. They consist of a basis connecting the tooth to the radular membrane, a stylus, and a cusp consisting of denticles (e.g. Runham and Thornton, 1967; Brooker and Macey, 2001). Tooth morphologies can be very diverse also within single radula. For example, in the case of the taenioglossan radula, there are four distinct teeth: within each row one central tooth, flanked to the sides by one lateral tooth and two marginal teeth (fig. 1c-g). In addition to the variety of tooth morphologies there is diversity in materialproperties of radular teeth. Within the last two decades, materialproperties of rhipidoglossan and docoglossan radular teeth had been studied extensively in Patellogastropoda and Polyplacophora; it has been shown that different elements, sometimes a substantial amount of iron, is incorporated in the chitinous teeth material making the teeth more wear resistant (e.g. Runham, 1961; Towe et al., 1963; Runham et al., 1969; van der Wal, 1989; Evans et al., 1991, 1992; Lee et al., 2003; van der Wal et al., 2000; Brooker et al., 2003; Shaw et al., 2010; Weaver et al., 2010; Brooker and Shaw, 2012; Lu and Barber, 2012; Ukmar-Godec et al., 2015). Since the amount and the composition of embedded elements differ between the previously studied mollusc species, the teeth have different mechanical properties (e.g. Weaver et al., 2010; Lu and Barber, 2012; Grunenfelder et al., 2014; Barber et al., 2015; Ukmar-Godec et al., 2017). However, radular teeth are not everlasting, and through the continuous growth of the radular ribbon from posterior to anterior new rows of teeth constantly enter the wearing zone while at the same time the teeth in the last row break loose (e.g. Runham, 1962, 1963; Runham and Isarankura, 1966; Isarankura and Runham, 1968; Mackenstedt and Märkel, 1987; Lowenstam and Weiner, 1989; Franz, 1990; Padilla et al., 1996; Shaw et al., 2008). Only the outermost few rows of teeth are actively used (e.g. Runham, 1963; Runham and Isarankura, 1966; Isarankura and Runham, 1968; Mackenstedt and Märkel, 1987, Franz, 1990; Padilla et al., 1996; Shaw et al., 2008).
In the mm-wave/THz reflectometry scenarios mentioned, the role of holistic multiscale tissue models based on com- putational electromagnetics (EM) is therefore becoming increasingly important to maximize the sensitivity and selec- tivity achieved by machine learning and regression analysis approaches. The major challenge in developing such a tissue model concerns the complex multiscale morphology of the skin, which determines its macroscopic EM properties. Most of the current EM skin models follow a heuristic repre- sentation of the skin topology as a multi-layer structure as proposed by Alekseev et al.  containing typically 3 to 4 homogenized dispersive layers. The material parameters of the latter are retrieved either from fitting models to experi- mental data  or in the framework of the effective material theory (EMT) using extended analytic mixing rules with asso- ciated multipole Debye models (e.g. the Havriliak-Negami relationship ) to account for the corresponding frequency dependence. A more rigorous approach builds upon a hierar- chically organized multiscale EM model that is rooted in the skin’s proper cellular structure. This is used in conjunction with a numerical homogenization procedure of the tissue’s microstructure with the aim of determining both the disper- sive and tensorial EM materialproperties. Such a multiscale approach has been pioneered by Huclova et al.  for human tissue analysis up to 1 GHz including the full skin layer morphology together with macroscopic textures like, e.g., the upper and deeper vessel plexus  to determine sen- sitivity and specificity of changes in skin components . An extension to this model up to 1 THz has been provided by Saviz et al.  using classical mixing rules for the homogenization of the various tissue layers, and was later complemented by Spathmann et al.  to include macro- scopic features such as hair follicles and skin wrinkles for frequencies in the range of 100 GHz – 10 THz.
The degree of methoxylation is often used as a key parameter for pectin application. The following examples show, however, that pectins with comparable molecular parameters (especially nearly identical DM) of different companies and even from one company but different production periods were far from similar in their materialproperties and gelling behaviour. The examples were the HMP 2A, 3A and 3G with DM about 69 % and the LMP 2C and 3E with DM 30 %, for the detailed values see Table 1.
diameter, as can be seen from electron micrographs depicted in Figure 2A. This microstructure benefits rapid electrolyte pene- tration through the open pore network and simultaneously increases the overall electrolyte-electrode interface area. Ac- cordingly, the Li-diffusion distance in the solid state is decreased and fast charge and discharge rates are enabled. A small number of larger particles with a diameter 1 mm in the network of LTO nanoparticles can be seen from the scanning electron micrographs. The particle morphology is largely maintained for modification temperatures of up to 800 8C, as no changes were observed by SEM and TEM characterization (Figure 2A–D). However, a stark impact on the optical materialproperties can be seen, as the powder changed its color from white to light blue and then to blue. At temperatures above 800 8C, distinct changes of the powder microstructure occur, since the powder density starts to rise markedly (Figure 2E–F). Simultaneously, the color of the samples transforms into dark blue (900 8C) and finally to black (1000 8C). The LTO nano- particles start to coalesce to larger primary particles with a diameter of about 100 nm at 900 8C (Figure 2E, inset). When adjusting the temperature to 1000 8C, all LTO nanoparticles were transformed into micrometer-large particles with some internal porosity (Figure 2F).
Abstract: This work investigates the application of lock-in thermography approach for solar loading thermography applications. In conventional lock-in thermography, a specimen is subjected to a periodically changing heat flux. This heat flux usually enters the specimen in one of three ways: by a point source, a line source or an extended source (area source). Calculations based on area sources are particularly well suited to adapt to solar loading thermography, because most natural heat sources and heat sinks can be approximated to be homogenously extended over a certain region of interest. This is of particular interest because natural heat phenomena cover a large area, which makes this method suitable for measuring large-scale samples. This work investigates how the extended source approximation formulas for determining thermally thick and thermally thin materialproperties can be used in a naturally excited setup, shows possible error sources, and gives quantitative results for estimating thermal effusivity of a retaining wall structure. It shows that this method can be used on large-scale structures that are subject to natural outside heating phenomena.
Though a general association of monovalent cations and pectin materialproperties, gelation and storage stability must be assumed and was also part of the conclusion from our previous studies, experimental evidence is still lacking. The tested samples differed not only in their content of monovalent cations but also in other parameters, like neutral sugar content and the molecular weight. Both parameters undergo changes depending on the demethoxylation method (Einhorn-Stoll et al., 2019; Kastner et al., 2019). It is well described that gelation is affected by neutral sugar side chains (Sousa, Nielsen, Armagan, Larsen, & Sørensen, 2015) and by the molecular weight (Ngouémazong et al., 2012; Hotchkiss et al., 2002). Furthermore, cleavage of neutral sugar side chains during storage competes for water with demethoxylation and backbone hydrolysis and may affect thermal degradation type and intensity.
Within the numerical model the materialproperties of the incoming metal strip are varied to check for the influence of the materialproperties on both the flatness as well as the residual stress distribution across the sheet thickness after levelling. According to the considered material behavior under low cyclic loading, the material parameters considered are the initial yield stress ı y,0 and the parameters describing kinematic hardening C and Ȗ. The initial yield stress ı y,0
A new experimental program on shotcrete and the evaluation of three advanced constitutive models for shotcrete, i.e., the Meschke model, the Schädlich model and the SCDP model, on the basis of the test data, were presented. The present paper closes the gap between the outdated experimental data on shotcrete available in the literature on the one hand and the nowadays available advanced constitutive models for representing the complex material behavior of shotcrete on the other hand. The new experimental program concentrated on the evolution of materialproperties of young shotcrete up to the age of 28 days as well as on the shrinkage and creep behavior, tested on sealed specimens up to the age of 56 days. Experiments were performed on two different types of specimens, i.e., drill cores sampled from spray boxes and directly sprayed specimens, the latter especially for experiments at very early shotcrete ages. The following conclusions can be drawn from the experimental program: • The application of directly sprayed specimens from tubular molds proved to be a suitable
According to the graph, all treatments with polystyrene have enhanced hydrophobic properties when compared to both unmodied and tosylated wood: aer ve days in water, unmodied wood gained about 160% water, while all wood– polystyrene composites only gain about 70%. Wood samples with polystyrene in lumen only (St experiment) also show a clear reduction in water uptake similar to St3 in the rst water- soaking cycle. It is well known that lumen lling by polymers decreases the space available for water, blocks cell cavities and consequently retards or avoids water entrance into the cell walls. 30–32 Interestingly, aer the rst drying cycle better results
Cross-laminated timber (CLT) is a planar structural element, consisting of several layers of timber boards glued on their wide faces but not necessarily on their narrow faces. The layers are stacked perpendicular to each other, with the outer layers having the same orientation. Through this design, CLT is a member with enhanced stiffness and strength, and favorable shrinking/swelling behavior compared to regular timber, whose mechanical properties in grain direction are significantly different from across the grain. CLT can be used in panel-like structures such as walls and slabs, making structural timber an appealing alternative to steel or concrete structures. Nowadays, in engineering practice, the finite element method is used to predict the response and load-bearing capacity of structures, based on a discretization by shell elements in case of planar structural members. For layered structures, shell elements can only be used if homogenized cross-sectional stiffness properties are available. In this contribution, the homogenized parameters of a shell stiffness tensor for CLT composed of five layers of spruce wood with equal layer thickness of 20 mm are derived, see also .
The semiempirical EAM has been successfully applied to wide range of metal clus- ters, including homoatomic systems [105, 106, 157, 170, 171] as well as nanoalloys [172, 173, 174, 175]. As a simple model potential the EAM is particularly suitable for the search of the lowest-energy structures of clusters, which has made it a popular computational method to perform global optimizations [105, 106, 157, 174, 175]. In this thesis an analytic MEAM is used to calculate the energy of Li and Na clusters. It was initially developed for bulk alkali metals and applied to various properties of these systems, e.g. the Debye temperature, heat capacity or surface energy . The results were in good accordance with other theoretical methods and experiments, therefore we were optimistic that an application to alkali clusters would be successful. Initial, pre- liminary investigations, published as bachelor thesis , showed the applicability of this analytic modified EAM to sodium clusters. Three isomers of Na N clusters (with 2 ≤ N ≤ 60) had been considered for the global optimization process. Due to the short time available for the bachelor thesis, only a limited investigation of the clusters’ PES was possible. This was not a problem within the present study, where a very thorough GEO of the clusters and a comprehensive structural and energetic analysis could be performed. Each cluster size could be studied in more detail, more isomers and larger cluster sizes could be considered. Additionally, some minor errors have been removed, which enhances the efficiency and accuracy of the source code, used for the GEO of the alkali clusters. Moreover, it should be stressed that none of the results, obtained within the bachelor project, have been used for the investigations within the present study. According to the MEAM, used in the present study, the total energy of a system can be described via three terms , where the first two terms, the embedding energy F (ρ h i ) and the pair potential φ(r ij ), are also included in the original version of the EAM [159, 160]. The embedding energy depends on the interatomic distances r ij through the hosts’ electron density ρ h i at position i, whereas the pair potential directly depends on the distance between two atoms, with one atom being located at position i and the other one being located at position j. The electron density ρ h i originates from the pres- ence of the other atoms of the system. The third energetic contribution M (P i h ) is the aforementioned modification term that corrects the assumption of linearly superposing spherically atomic electron densities and it is a function of the second order of the hosts’ electron density P i h at site i . Hence, the total energy of a system consisting of N atoms can be described by the following equation:
the tests performed are in the short-time area, with the highest frequency in the region up to 2000 hours. Only few points are present in the normal creep design area of component life-time of 100.000-200.000 hours. Figure 46 shows the ap- plied stress frequency, where it is obvious that the normal creep limits of 100-130 MPa at 540°C, are in the lower left part of the applied stress frequency diagram, which is in line with the Figure 45 – i.e. higher levels of stresses are leading to the shorter times to rupture. Finally, Figure 47 shows temperature distribution, where it is obvious that 3 main target temperatures of 500, 550 and 600°C take up most of the test numbers. These three diagrams clearly demonstrate the gap between creep testing and design in creep region – i.e. the long-time properties are usually derived from short-term creep tests on much higher stress levels. Temperature coverage is, in contrast, equivalent to the design application of the material, sug- gesting the isothermal nature of testing approach applied for the testing.
All of these requirements are valid for both targets to be used as radioactive sources for, e.g., nuclear spectroscopy investigations and targets to be applied in accelerator experiments. Thickness and homogeneity are important in targets to be used for, e.g., activity measurements in order to reduce scattering and absorption of radiations (i.e., back-scattering, self-scattering, and self-absorption) in the sample and in its support. At the same time, targets to be used in accelerator experiments need to be thin and uniform to allow various charged particles to pass through the deposit without undue energy loss. Chemical and radiochemical purities are of course important as interfering radioactive background has always to be avoided. As regards the cracking of the layers, this usually gains more attention in the case of irradiation experiments as cracks and other aberrations in the target result in an increased tendency to break under the thermal stress of the beam . This can lead to material flaking off the target backing, resulting in dead spots on the target face, the wasting of isotopically pure materials and contamination of the experimental area . Further, the target and its backing experience an increase in temperature due to irradiation, which results in warping and often breaking of the deposited layer . Therefore structural rigidity of the produced targets is another fundamental requirement.
( ε 0 f ) n 0 (4)
To determine the cyclic materialproperties, strain-controlled fatigue tests on unnotched specimens, Figure 2 a, were conducted. To measure the strain, a clip-gauge extensometer with a measuring length of 5 mm was used. The strain amplitudes were chosen to be between 0.14% and 0.80%, so that the resulting numbers of load cycles covered the range of approximately 100 to 5·10 6 . These tests were conducted in accordance with Standard SEP 1240 [ 19 ]. Since SEP 1240 is a German standard, it shall be described briefly: Strain-controlled fatigue tests are conducted at different levels. The strain amplitude is controlled and kept constant for the whole test. The axial reaction force acting on the specimen is measured and recorded throughout the test. The criterion used to identify the number of cycles for crack initiation N is a drop or increase in the measured stress amplitudes of 10% compared to the stabilized stress amplitude [ 19 ]. The result of a strain-controlled test is a data triplet of the strain amplitude, stress amplitude, and number of cycles endured. The determined number of cycles is usually valid for crack initiation. The stress amplitude σ a , on the other hand, is determined at the half-life (N/2) of the specimen, where the material behavior has already stabilized after the so-called initial cyclic hardening or softening that occurs for many metallic materials. For a detailed explanation on the evaluation of such test results, see, e.g., [ 20 ]. The cyclic properties of the strain–life curve σ 0 f , b, ε 0 f , and c are determined by regression analysis of the individual test results (see SEP 1240 [ 19 ], also described in [ 20 ]). The properties of the cyclic stress–strain curves are calculated from the aforementioned properties using Equations (3) and (4).
Abstract Most studies dealing with materialproperties of sandstones are based on a small data set. The present study utilizes petrographical and petrophysical data from 22 selected sandstones and *300 sandstones from the litera- ture to estimate/predict the material and weathering behaviour of characteristic sandstones. Composition and fabric properties were determined from detailed thin sec- tion analyses. Statistical methods applied consist of data distributions with whisker plots and linear regression with confidence regions for the petrophysical and weathering properties. To identify similarities between individual sandstones and to define groups of specific sandstone types, principal component and cluster analyses were applied. The results confirm an interaction between the composi- tion, depositional environment, stratigraphic association and diagenesis, which leads to a particular material behaviour of sandstones. Three different types of pore radii distributions are observed, whereby each is derived from different pore space modifications during diagenesis and is associated with specific sandstone types: (1) bimodal with a maximum in capillary and micropores, (2) unimodal unequal with a maximum in smaller capillary pores and (3) unimodal equable with a maximum in larger capillary pores. Each distribution shows specific dependencies to water absorption, salt loading and hygric dilatation. The strength–porosity relationship shows dependence on the content of unstable lithic fragments, grain contact and type