Nominal Samples Research Articles

Investigation into the fracture behavior of ZK60 Mg alloy rolling sheet under different stress triaxiality

In order to investigate the fracture behavior of the ZK60 Mg alloy rolling under different stress triaxiality, the different nominal stress triaxiality samples were well-designed, and the in-situ DIC tensile tests were carried out. The finite element method (FEM) model was validated by experimental results and the stress triaxiality evolution of samples was determined by modeling. The fracture strain of the ZK60 Mg alloy was non-monotonic with the nominal stress triaxiality increase and the best deformation performance of the central hole sample was indicated via the experimental and modeling results. The low stress triaxiality gradient of the central hole sample led to better deformation performance in terms of the macroscopic mechanical response. The transformation of the fracture mechanism from shear transgranular fracture to intergranular fracture and then to transgranular fracture during the stress triaxiality increased from 0 to 2/3 and was revealed via scanning electron microscope (SEM) characterization and FEM modeling. To further confirm the above fracture mechanism, X-ray computed tomography (XCT) was carried out to characterize the micro damage volume fraction and morphology. Due to the transgranular fracture induced by the high stress triaxiality at the initial fracture position of the central hole sample, the micro damage was smaller, delaying the fracture failure and achieving higher strain.

Behaviour of polymer-filled–concrete–steel double-skin tubular columns under combined lateral impact and axial compression loading

The paper presents a study on the suitability of using a Polymer as a protective layer for critical structural elements prone to impact damage. Conventional damage mitigation methods include using an outer steel jacket with a void, protecting the inner concrete-steel composite column. Whilst it is usually found that the outer steel jacket can partially negate the impact load, the inner column still experiences a significant brunt of the impact load. In order to minimise the damage to the overall critical structural element, a concept of a Polyurethane Polymer-Filled–Concrete–Steel Double-Skin Tubular Column is proposed. Scaled-down versions of two polymer-filled double-skin column configurations were tested under low-velocity impact using a drop tower. The pre and post-damage columns were tested for their axial capacities. These polymer-filled columns were critically compared to their nominal samples without the Polyurethane fill. It was shown that the mid-span deflection and localised indentations were reduced by 17%, and the localised deformations (at the point of impact) were reduced by up to 70% overall. The columns with Polyurethane also showcased retention of 70% of axial capacity post-impact, whilst the nominal sample was only capable of retaining 48%. Finally, the intrinsic properties of Polyurethane were discussed along with a critical discussion on its ability and mechanism on how energy is dissipated by comparing mechanical and chemical properties.

Exploring the structural and magnetic trends in Ba0.9Sm0.1Fe12−xAlxO19 M-type Hexaferrites

The current study describes the structural and magnetic properties of Ba0.9Sm0.1Fe12−x Al x O19 (x = 0.0, 0.5, 1.0, 2.0, 3.0) M-type hexaferrites. The conventional ceramic route was implied to prepare all the nominal samples. Morphological analysis suggested the non-presence of secondary phases as well as the formation of the hexaferrites material. X-ray Diffraction technique was used for structural analysis from which microstructural parameters are calculated and discussed. Magnetic properties are measured at room temperature. The saturation magnetization (Ms) and coercivity (Hc) values show a cyclic and converse trend for synthesized samples. Firstly, a decrease in Ms and an increase in Hc was observed up to intermediate dopant incorporation and becomes converse for higher doping levels. The maximum coercivity and minimum magnetization are observed for Ba0.9Sm0.1Fe11Al1O19. The c/a and Mr/Ms ratio suggest the formation of perfect M-type hexaferrites. This work suggests that synthesized material is a good option for magnetic applications e.g., transformer and inductor cores, microwave devices, recording heads, and magnetic shielding.

Magnetization dynamics of amorphous and nanocomposite CoFeMnNbSiB films with the addition of excess cobalt and boron

We report on the magnetic and structural characterization of Co75.4Fe2.3Mn2.3Nb4Si2B14 (nominal) nanocomposite thin films and compositional derivatives formed by the co-sputtering of additional cobalt and boron followed by ex-situ vacuum annealing at 520 °C for different annealing times. The structural and compositional analyses of these samples were performed using transmission electron microscopy and atom probe tomography (APT). For the quasi-static magnetic measurements, vibrating sample magnetometry (VSM) was used and the magnetization dynamics was studied using a custom-built broadband ferromagnetic resonance (FMR) instrument with a frequency range of 1–65 GHz and fields up to 1.6 T. Two strong resonances were observed for the annealed nominal and B-added samples whereas a dominant single resonance was observed for all as-deposited and all annealed Co-added samples. This observation correlates with APT results where Mn-rich columnar structures were observed in the as-deposited nominal and Co-added annealed films. Whereas, a nearly equiaxed morphology of the crystalline phase was observed for annealed nominal and B-added films. Hence, FMR spectroscopy was found to be sensitive to the different phases present in the samples and differences in morphology. The quasi-static magnetic properties measured using VSM were not able to distinguish between the individual contributions. However, they provide important information regarding the overall magnetization. The VSM results suggested that short time annealing of the nominal composition results in better soft magnetic properties compared to the derivative compositions that were investigated in this study.

Securing the Inter-Spacecraft Links: Physical Layer Key Generation From Doppler Frequency Shift

In this work, we propose a secret key generation procedure specifically designed for the inter-spacecraft communication links. As a novel secrecy source, the spacecrafts utilize Doppler frequency shift based measurements. In this way, the mobilities of the communication devices are exploited to generate secret keys, where this resource can be utilized in the environments that the channel fading based key generation methods are not available. The mobility of a spacecraft is modeled as the superposition of a pre-determined component and a dynamic component. We derive the maximum achievable secret key generation rate from the Doppler frequency shift. The proposed secret key generation procedure extracts the Doppler frequency shift in the form of nominal power spectral density samples (NPSDS). We propose a maximum-likelihood (ML) estimation for the NPSDS at the spacecrafts, then a uniform quantizer is utilized to obtain secret key bits. The key disagreement rate (KDR) is analytically obtained for the proposed key generation procedure. Through numerical studies, the tightness of the provided approximations is shown. Both the theoretical and numerical results demonstrate the validity and the practicality of the presented physical layer key generation procedure considering the security of the communication links of spacecrafts.

Highly selective and sensitive differential pulse voltammetric method based on poly(Alizarin)/GCE for determination of cefadroxil in tablet and human urine samples

Cefadroxil, which belongs to the first-generation cephalosporin class of β-lactam antibiotics, develops bacterial resistance necessitating development of sensitive and selective method for its determination. This paper reports determination of cefadroxil in tablet and human urine samples using poly(alizarin)/GCE. CV and EIS results confirmed deposition of a conductive and electroactive polymer film. Relative to the peak of cefadroxil at the bare electrode, an irreversible oxidative peak at poly(Aliz)/GCE with four folds of current and much reduced potential verified improvement on electrode surface conductivity and effective surface area. DPV current varied linearly with concentration of cefadroxil in the range 1.0 × 10−7–1.0 × 10−4 M with LoD, and LoQ of 8.1 × 10−9, and 2.7 × 10−8 M, respectively. Detection of 99. ± 3.01 and 99.5 ± 2.03% cefadroxil of the 10.0 and 20.0 µM nominal tablet samples, respectively showed agreement between the detected amount and tablet label. Spike recovery in the range 99.5–100.5% in tablet and human urine samples and interference recovery results in the presence of selected potential interferents in tablet sample with percent error of 0.0–4.9% validated the applicability of the method for determination of cefadroxil in real samples. Compared with previously reported works on cefadroxil determination, relatively wider linear range and extremely low limit of detection of the present method along with its excellent accuracy and selectivity make the method an outstanding candidate for determination of cefadroxil in real samples.

125Te NMR for structural investigations in phase change materials: Optimization of experimental conditions coupled to NMR shift prediction

Phase Change Materials as those of the Ge-Sb-Te ternary system are of great interest for technological applications. Properties of these compounds are strongly related to presence of vacancies and structural investigations remain challenging. In this paper we evidence that 125Te NMR in natural abundance and using commercial systems at intermediate field (14.1 ​T) together with NMR parameters prediction can contribute to improve understanding of electronic structure of such systems. GeTe is a typical phase change material, whose structure contains germanium vacancies, even in its stoichiometric form, giving it metallic properties. Here, we use nominal Ge50Te50 and Ge48Te52 crystalline samples as an example to optimize the WURST-CPMG technique, a powerful technique to record wide NMR spectra which has not yet been used on 125Te. The goal was to minimize the time devoted to experiments as well as maximize the signal-to-noise ratio in order to detect small intensity signals directly linked to vacancies. Virtual Crystal Approximation (VCA) calculations performed with WIEN2K helped to interpret the NMR spectra. For Te-based crystalline conducting samples the best experimental results were obtained using 3.2 ​mm thin wall rotors with diluted samples 40 ​vol% GeTe-60 ​vol% SiO2. In addition to the WURST-CPMG technique, high resolution spectra using MAS as implemented in the pj-MAT technique allowed us to identify the distributions of chemical shift parameters in the high intensity contribution of the 1D spectra. The NMR spectra recorded on the samples showed that an addition of Tellurium in the stoichiometric Ge50Te50 sample leads to an important broadening of the spectrum together with a shift of the lines. According to VCA calculations it could be attributed to a distribution of concentrations of germanium vacancies in the sample and it would appear that Knight Shift but also Chemical Shift could contribute in similar proportion to the NMR line position when metavalent bonding is invoked.

Applications of deep learning in big data analytics for aircraft complex system anomaly detection

Big data analytics with deep learning approach have attracted increasing attention in transportation engineering, involving operations, maintenance, and safety. In commercial aviation sectors, operational, and maintenance data produced on modern aircraft is increasing exponentially, and predictive analysis of these data is an exciting and promising field in aviation maintenance, which has a potential to revolutionize aerospace maintenance industry. This study illustrates the state-of-the-art applications of deep learning in big data analytics for predictive maintenance and a real-world case study for commercial aircraft. A Long Short-Term Memory network based Auto-Encoders (LSTM-AE) is proposed for complex aircraft system fault detection and classification, which makes use of the raw time-series data from heterogeneous sensors. The proposed method uses nominal time-series samples corresponding to healthy behavior of the system to learn a reconstruction model based on LSTM-AE framework. Then the system health index (HI) and fault feature vectors are derived from the reconstruction error matrix for fault detection and classification. The proposed method is demonstrated on a real-world data set from a commercial aircraft fleet. The typical PCV faults as well as the 390 F sensor and 450 F sensor faults due to sense line air leakage are successfully detected and distinguished based on the extracted features. The case study results show that the computed HI can effectively characterize the health state of the aircraft system and different fault types can be identified with high confidence, which is helpful for line fault troubleshooting.

Solid Solution Li(Ni,Mn,Co,Fe)O2 Homogeneity Range

By the combustion of the starch-based gel the two series of the nominal composition samples were synthesize: Li1.1Co1−x(Ni0.33Mn0.33Fe0.33)xO2 (0 ≤ x ≤ 1) and Li1.1Ni1−x(Mn0.33Co0.33Fe0.33)xO2 (0 ≤ x ≤ 1). The estimation of the homogeneity range’s extension of the type ɑ-NaFeO2 layered solid solution Li(Ni,Mn,Co,Fe)O2 was based on the results of the x-ray phase analysis of the obtained samples. It was found that the solid solution was continuous at the Li1+γCoO2-Li1+γNi0.33Mn0.33Fe0.33O2 conode and limited at the Li1+yNiO2-Li1+γMn0.33Co0.33Fe0.33O2 conode. Within the isobaric-isothermal tetrahedron Li1+yNiO2-Li1+yMnO2-Li1+yCoO2-Li1+yFeO2, the position of the stable range of the solid solution Li(Ni,Mn,Co,Fe)O2 is shown by the Li1+yCoO2-Li1+yNi0.5Mn0.5O2-Li1+yFeO2 and Li1+yNiO2-Li1+yMn0.5Co0.5O2-Li1+yFeO2 sections.

Influence of oral health in the quality of life of preschoolers in a faculty-based practice in Rio de Janeiro

To evaluate the influence of oral health status on the quality of life of preschool children using the dmft and pufa indexes, crossing information with the B-ECOHIS questionnaire to achieve quality of life related to oral health (OHRQoL). All children, healthy, between 3 and 5 years old, with a primary dentition who sought dental care at the Department of Pediatric Dentistry and Orthodontics at Universidade Federal do Rio de Janeiro, during a period of 2 months, were selected and divided into two groups: advanced caries: dmft score ≥ 1 and pufa score ≥ 1 (G1) and moderate caries: dmft score ≥ 1 and pufa score = 0 (G2). An epidemiological survey of oral health using the dmft and pufa indexes, in addition to economic evaluation questionnaires and the B-ECOHIS questionnaire, was carried out and a quality of life survey was performed. Statistical tests were performed to compare nominal variables (Chi-square and Fisher’s exact test) and independent samples and their numerical variables (Mann–Whitney). Sixty-nine preschoolers were included, with a mean age of 54 months. The mean dmft scores were 6.72 (G1) and 1.05 (G2) (p < 0.001) and the mean pufa scores were 2.45 (G1) and 0 (G2). The B-ECOHIS questionnaire results in the child impact section (CIS) were 8.79 (G1) and 1.73 (G2). In the family impact section (FIS), the means for G1 and G2 were 5.76 and 1.10, respectively. The CIS and FIS presented a significant correlation (p < 0.001). The oral health condition affects preschoolers and their OHRQoL. The poorest oral health condition had a greater negative impact on the quality of life in both the families and the children.

Time for a comprehensive approach to the syndrome of fever in the tropics

Time for a comprehensive approach to the syndrome of fever in the tropics

Fusion of multiple formant-trajectory- and fundamental-frequency-based forensic-voice-comparison systems: Chinese /ei1/, /ai2/, and /iau1/

This study investigates the fusion of multiple formant-trajectory- and fundamental-frequency-trajectory-based (f0-trajectory-based) forensic-voice-comparison systems. Each system was based on tokens of a single phoneme: tokens of Chinese /ei1/, /ai2/, and /iau1/ (numbers indicate tones). Human-supervised formant-trajectory and f0-trajectory measurements were made on tokens from a database of recordings of 60 female speakers of Chinese. Discrete cosine transforms (DCT) were fitted to the trajectories and the DCT coefficients used to calculate likelihood ratios via the multivariate kernel density (MVKD) formula. The individual-phoneme systems were fused with each other and with a baseline mel-frequency cepstral-coefficient (MFCC) Gaussian-mixture-model universal-background-model (GMM-UBM). The latter made use of the entire speech-active portion of the recordings. Tests were conducted using high-quality recordings as nominal suspect samples and mobile-to-landline transmitted recordings as nominal offender samples. Fusion of the phoneme-systems with the baseline system via logistic regression did not lead to any substantial improvement in validity and reliability deteriorated.

Acoustic chemometrics for material composition quantification in pneumatic conveying — The critical role of representative reference sampling

Reliable monitoring of pneumatically conveyed particulate materials is critical for on-line detection and controlling material composition changes in the regimen of Process Analytical Technology (PAT), e.g. as the case investigated here: determination of varying concentration levels of extraneous material in a source stream. Results are reported from an experimental test campaign on a pilot-scale pneumatic conveying facility. Optimal sensor deployment and material flow rates are decisive parameters for signal quality and prediction performance. The test campaign resulted in an optimal sensor location/flow rate combination, based on which we present a validated prediction model (Partial Least Squares Regression model) for prediction of extraneous material concentration levels, with a RMSEP (rel) of 17.7% (RMSEP: 0.92) and r 2 of 0.95. The present approach is based on acoustic chemometrics (a.c.). The impact of nominal reference values vs. representative reference values used as response variables in prediction models is discussed. Optimal reference values were obtained through the use of representative sampling equipment (based on Theory of Sampling, TOS), specifically designed for pneumatic conveying systems, and compared with nominal concentration levels, allowed an improvement of the prediction model: (RMSEP (rel) , of 15% (RMSEP: 0.85) and r 2 0.95). Whilst the present experimental rig test resulted in relative minor quantitative improvements only, representative reference samples, required for prediction models, are essential when nominal concentration levels cannot be determined or are unknown, which is usually the case in enclosed pneumatic conveying systems, the target for this study. All prediction results are validated with independent data (test set validation). We calibrate/validate a successful PLS-R model, based on optimal sensor location/flow rate combination for prediction of extraneous material concentration levels in pneumatically conveyed material streams. The impact of nominal reference values vs. representative reference values used as response variables in prediction models is discussed. Schematic drawing of pneumatic conveying system indicating sensor locations and source of y-values (representative/nominal). ► Prediction model for material composition quantification in pneumatic conveying ► Test campaign resulted in an optimal sensor location/flow rate combination ► Reliable reference values obtained through the use of a representative sampler ► Comparison of nominal versus representative reference samples as response variable ► All prediction results are validated with independent data (test set validation).

Mitochondrial and nuclear DNA analysis revealed a cryptic species and genetic introgression in Littorina sitkana (Mollusca, Gastropoda)

We investigated mitochondrial and nuclear DNA genotypes in nominal Littorina sitkana samples from 2 localities in Eastern Hokkaido, northern Japan. Our results indicated the existence of cryptic species. In the analysis of partial mitochondrial Cytchrome b gene sequences, haplotypes of L. sitkana samples were monophyletic in a phylogenetic tree with orthologous sequences from other Littorina species, but were apparently separated in 2 clades. One included typical L. sitkana (CBa clade) samples, which formed a clade with an allopatric species, L. horikawai. The other, CBb, was independent from CBa and L. horikawai. Haplotypes of the mitochondrial 16S rRNA gene also separated into 2 clades. We additionally examined intron sequence of the heat shock cognate 70 (HSC70) nuclear gene and identified 17 haplotypes. These were also separated into 2 clades, HSCa and HSCb. Among the examined Hokkaido samples, 60% of individuals were heterozygotes. However, each heterozygote consisted of haplotypes from the same clade, HSCa or HSCb, and no admixture of HSCa and HSCb haplotypes was observed. These results indicate reproductive isolation between the 2 clades. Among the genotyped Hokkaido samples, 93% of individuals had CBa+HSCa or CBb+HSCb genotypes, and 7% had CBb+HSCa genotypes. The discrepancy between the mtDNA and nuclear DNA haplotypes in a few individuals may have been caused by genetic introgression due to past hybridization.

Impact of Tuning Molar Ratio in the Starting Materials: Magneto-Transport Features of Hybrid YSr2Ru0.9Cu2.1O7.9

The impact of slightly tuning molar ratio in the starting materials on the physical properties of 1212-type rutheno-cuprate, YSr2Ru0.9Cu2.1O7.9 (nominal) samples prepared under four synthesis approaches are reported. Interestingly, all samples clearly show the differences in the physical properties of the samples prepared under different synthetic protocols. However, neither XRD nor EDX reveal any notable differences in the crystal structure or sample composition. All the samples exhibit magneto-superconducting properties (Hext=5 Oe) which are slightly varied with synthetic approaches. The high field (Hext=10 kOe) temperature dependence of magnetization data shows a sharp ferromagnetic transition around 150 K and all the samples obey Curie–Weiss linear behavior above 180 K. The experimental effective paramagnetic moment for the various samples is in the range of 2.5 and 2.7μB/Ru which are in line with the literature report. The magnetization, M(H) isotherm curves measured at 5 K and −10 kOe≤H≤10 kOe conditions reveal weak ferromagnetic-like hysteresis loops for all samples with returning moment (Mr) and coercive field (Hc), whereas the high field M(H) loops indicate soft ferromagnetic behaviors with magnetic saturation. The saturation moment of the samples is slightly varied with the synthesis approaches. None of the samples showed bulk superconductivity (\(T_{\mathrm{c}}^{R = 0})\) down to 2 K, while all samples show onset transitions (\(T_{\mathrm{c}}^{\mathrm{onset}}\)) except the sample prepared by approach-3. The latter approach sample shows semiconducting behavior down to 2 K. The \(T_{\mathrm{c}}^{\mathrm{onset}}\) noticed at 34 K, 12 K, and 6 K for the sample prepared by approach-1, 2, and 4, respectively. The nearly linear dependence suggests that hopping conduction is dominant in certain temperature range for all samples. The magneto-transport features of these samples exhibit maximum magnetoresistance (MR) at low temperatures. Remarkably, the sample prepared by approach-1 shows largest −MR about 77% at low temperature 2 K and H=90 kOe which stimulates for further investigations. Among the four synthesis approaches employed in the present study, we can probably suggest that the approach-1 (0.5Y2O3+0.5SrO2+1.5SrCuO2+0.9RuO2+0.6CuO) is the preferable method to achieve the best sample (in terms of magneto-transport features).

Structural and hyperfine evolution of the (Fe 79Mn 21) 1− xCu x system under milling time

The evolution with milling time ( t m) of the structural and hyperfine properties of mechanically alloyed (Fe 79Mn 21) 0.85Cu 0.15 and (Fe 79Mn 21) 0.70Cu 0.30 nominal composition samples are reported. The samples milled during t m = 1, 3, 6, 9, 12, 15 and 18 h are characterized by X-ray diffraction (XRD) and Mössbauer spectroscopy. From the XRD results two phases are observed, a BCC one corresponding to α-Fe(Mn, Cu) and a FCC-phase associated to Fe–Mn–Cu solid solution. Mössbauer spectra show complex structure evidencing several Fe environments. Two hyperfine magnetic field distributions were used to reproduce the spectra, a high magnetic field interaction ascribed to the BCC phase and a low hyperfine magnetic field distribution linked to the FCC solid solution. An increment in the average hyperfine magnetic field ( B hf) and in the isomer shift ( δ) values of the low hyperfine magnetic field distribution is observed when the milling time increases. All the structural and hyperfine parameters remain without changes after 9 h of milling. Once this stationary regime is archived, the B hf of the (Fe 79Mn 21) 0.85Cu 0.15 sample resulted higher than that of the (Fe 79Mn 21) 0.70Cu 0.30 one.

Hall effect and sign reversal in Gd(Ba 2−xNd x)Cu 3O 7+δ

We have investigated the Hall measurement of Gd(Ba 2− x Nd x )Cu 3O 7+ δ with x=0, 0.05, 0.1, 0.15, and 0.2 in a magnetic field of 0–1 T. The nominal samples has been prepared by the conventional solid-state reaction technique. The iodometric titration experiment was carried out for samples. The Rietveld analysis of the X-ray diffraction patterns indicates that samples are mainly single phase. The normal state Hall coefficient behaves as 1/ T in all samples. All samples with nominal compositions show single sign reversal with variation of magnetic field and temperature. The Hall resistivity of the samples with x=0 and 0.1 close to the superconducting transition temperature changes its sign with decreasing temperature and tends to a minimum − Δ max, and then monotonically goes to zero. The absolute value of − Δ max decreases with the increase of magnetic field. This can be qualitatively explained by a model calculation based on the time-dependent Ginsburg–Landau theory.

NMR-melting-curve study of bitumen of different types and origin

The nuclear magnetic resonance (NMR) melting-curve method, employing measurement of the temperature-dependent width of the1H NMR spectrum, was used in a comparative study of softening of various industrial bitumen types (BIT 60 and BIT 90) produced by different manufacturers. Out of three manufacturers involved in the study, only the bitumen samples of one of them exhibited the expected regularity — the NMR melting curves formed two well-defined groups, one belonging to BIT 60-type samples and the other to BIT 90-type, and the BIT 90 samples showed softer melting characteristics. This indicates a reproducible industrial production process and reliable classification into different bitumen types. The NMR melting curves of nominal BIT 60-type samples of the other two manufacturers are scattered irregularly over a large range, extending much beyond the total span of the BIT 60 and BIT 90 curves of the first manufacturer. Hence the classification of these samples into one bitumen type (BIT 60) makes less sense.

Failure mode and weakening effect of water on sandstone

Previous studies have shown that brittle strength of a rock is generally reduced in the presence of water. However, for siliciclastic rocks, there is a paucity of data on the waterweakening behavior in the cataclastic flow regime. To compare the weakening effect of water in the brittle faulting and cataclastic flow regime, triaxial compression experiments were conducted on the Berea, Boise, Darley Dale, and Gosford sandstones (with nominal porosities ranging from 11% to 35%) under nominally dry and saturated conditions at room temperature. Inelastic behavior and failure mode of the nominal dry samples were qualitatively similar to those of water‐saturated samples. At elevated pressures, shear localization was inhibited, and all the samples failed by strain hardening. The compactive yield strengths (associated with the onset of shear‐enhanced compaction) in the saturated samples were lower than those in the dry samples deformed under comparable pressure conditions by 20% to 70%. The reductions of brittle strength in the presence of water ranged from 5% to 17%. The water‐weakening effects were most and least significant in the Gosford and Berea sandstones, respectively. The relation between water weakening and failure mode is consistently explained by micromechanical models formulated on the basis that the specific surface energy in the presence of water is lowered than that in vacuum by the ratio λ. In accordance with the Hertzian fracture model the initial yield stress in the compactive cataclastic flow regime scales with the grain‐crushing pressure, which is proportional to λ3/2. In the brittle faulting regime, damage mechanics models predict that the uniaxial compressive strength scales with λ1/2. In the presence of water the confined brittle strength is lower due to reductions of both the specific surface energy and friction coefficient.

Anomalous magnetic disaccommodation in yttrium iron garnet

An alternative approach to account for the oxygen loss at sintering temperatures in YIG allows an explanation to the not yet elucidated accommodation effect observed in the magnetic disaccommodation spectrum of nominal stoichiometric samples below 130 K; i.e., the observed time increase of the initial permeability μi after demagnetizing the samples instead of the usual time decrease. In single phased YIG samples sintered under low oxygen pressures, electric balance considerations leads to the existence of interstitial cations. These cations are expected to affect the normal superexchange interactions and the ferromagnetic ordering, obstructing the formation and movement of the domain walls after the sample has been demagnetized; the net effect would be a μi smaller than that of the sample free of interstitials. However, given a suitable energy of activation at a given temperature, the potential energy barriers would be surmounted and the interstitial magnetic moments would become more or less arranged into the ferromagnetic order, attaining a minimum of free energy. Thus, the impediments to domain wall formation and movement would be at least partially eliminated, causing the observed accommodation outcome.