Large Values Research Articles

Risk chain identification of single-vehicle accidents considering multi-risk factors coupling effect.

The real-time monitoring on the risk status of the vehicle and its driver can provide the assistance for the early detection and blocking control of single-vehicle accidents. However, complex risk coupling relationship is one of the main features of single-vehicle accidents with high mortality rate. On the basis of investigating the coupling effect among multi-risk factors and establishing a safety management database throughout the life cycle of vehicles, single-vehicle driving risk network (SVDRN) with a three-level threshold was developed, and its topology features were analyzed to assessment the importance of nodes. To avoid the one-sidedness of single indicator, the multi-attribute comprehensive evaluation model was applied to measure the comprehensive effect of characteristic indicators for nodes importance. A algorithm for real-time monitoring of vehicle driving risk status was proposed to identify key risk chains. The result revealed that improper operation, speeding, loss of vehicle control and inefficient driver management were the sequence of top four risk factors in the comprehensive evaluation result of nodes importance (mean value = 0.185, SD = 0.119). There were minor differences of 0.017 in the node importance among environmental factors, among which non-standard road alignment had the larger value. The improper operation and non-standard road alignment were the highest combination correlation of factors affecting road safety, with the support of 51.81% and the confidence of 69.35%. This identification algorithm of key risk chains that combines node importance and its risk state threshold can effectively determine the high-frequency risk transmission paths and risk factors through multi-vehicle test, providing a basis for centralization management of transport enterprises.

Modulation of Electrokinetic Potentials Using Graphene-Based Surfaces and Variable Substrate Charge Density.

Enhanced electrokinetic phenomena, manifested through the observation of a large streaming potential (Vs), were obtained in microchannels with single-layer graphene (SLG)-coated and few-layer graphene (FLG)-coated surfaces. In comparison to silicon microchannels, the Vs obtained for a given pressure difference along the channel (ΔP) was higher by 75% for the graphene-based channels, with larger values in the SLG case. Computational modeling was used to correlate the surface charge density, tuned through plasma processing, and related zeta potential to measured Vs. The implications related to deploying lower dimensional material surfaces for modulating electrokinetic flows were investigated.

How Representative Are European AERONET-OC Sites of European Marine Waters?

Data from the Ocean Color component of the Aerosol Robotic Network (AERONET-OC) have been extensively used to assess Ocean Color radiometric products from various satellite sensors. This study, focusing on Ocean Color radiometric operational products from the Sentinel-3 Ocean and Land Colour Instrument (OLCI), aims at investigating where in the European seas the results of match-up analyses at the European marine AERONET-OC sites could be applicable. Data clustering is applied to OLCI remote sensing reflectance from the various sites to define different sets of optical classes, which are later used to identify class-based uncertainties. A set of fifteen classes grants medium-to-high classification levels to most European seas, with exceptions in the South-East Mediterranean Sea, the Atlantic Ocean, or the Gulf of Bothnia. In these areas, spectra are very often identified as novel with respect to the generated set of classes, suggesting their under-representation in AERONET-OC data. Uncertainties are finally mapped onto European seas according to class membership. The largest uncertainty values are obtained in the blue spectral region for almost all classes. In clear waters, larger values are obtained in the blue bands. Conversely, larger values are shown in the green and red bands in coastal and turbid waters.

Dual-phase nano-glass-hydrides overcome the strength-ductility trade-off and magnetocaloric bottlenecks of rare earth based amorphous alloys

Metal-hydrogen systems have attracted intense interest for diverse energy-related applications. However, metals usually reduce their ductility after hydrogenation. Here, we show that hydrogen can take the form of nano-sized ordered hydrides (NOH) homogeneously dispersed in a stable glassy shell, leading to remarkable enhancement in both strength and ductility. The yield strength is enhanced by 44% and the plastic strain is substantially improved from almost zero to over 70%, which is attributed to the created NOH and their interplay with the glassy shell. Moreover, the hydride-glass composite GdCoAlH possesses a giant magnetic entropy change (−ΔSM) of 18.7 J kg−1K−1 under a field change of 5 T, which is 105.5% larger than the hydrogen-free sample and is the largest value among amorphous alloys and related composites. The prominent ΔSM-ductility combination overcomes the bottlenecks of amorphous alloys as magnetic refrigerants. These results provide a promising strategy for property breakthrough of structural-functional alloys.

Affective responses to acute exercise: A meta-analysis of the potential beneficial effects of a single bout of exercise on general mood, anxiety, and depressive symptoms.

Acute exercise elicits various biobehavioral and psychological responses, but results are mixed with regard to the magnitude of exercise-induced affective reactions. This meta-analysis examines the magnitude of general mood state, anxiety, and depressive symptom responses to acute exercise while exploring exercise protocol characteristics and background health behaviors that may play a role in the affective response. A total of 2,770 articles were identified from a MEDLINE/PubMed search and an additional 133 articles from reviews of reference sections. Studies had to have measured general mood before the acute exercise bout and within 30 minutes after exercise completion. Effect sizes were estimated using Hedges' g, with larger values indicating improvement in the outcome measure. A total of 103 studies were included presenting data from 4,671 participants. General mood state improved from pre-exercise to post-exercise (g = 0.336, 95%CI = 0.234,0.439). Anxiety (g = 0.497, 95%CI = 0.263,0.730) and depressive symptoms (g = 0.407, 95%CI = 0.249,0.564) also improved with exercise. There was substantial and statistically significant heterogeneity in each of these meta-analyses. This heterogeneity was not explained by differences in participants' health status. Meta-regression analyses with potential moderators (intensity of exercise, mode of exercise, usual physical activity level, or weight status of participants) also did not reduce the heterogeneity. This meta-analysis shows significantly improved general mood, decreased anxiety, and lower depressive symptoms in response to an acute bout of exercise. There was substantial heterogeneity in the magnitude of the effect sizes, indicating that additional research is needed to identify determinants of a positive affective response to acute exercise.

ОЦІНКА ОБЧИСЛЮВАЛЬНОЇ СКЛАДНОСТІ ГЕНЕТИЧНОГО АЛГОРИТМУ

The article is devoted to the estimation of computational complexity of a genetic algorithm as one of the key tools for solving optimisation problems. The theoretical aspects of computational complexity of algorithms and the interrelation of elements of a genetic algorithm are considered. The main types of computational complexity of algorithms are described: time, simple and asymptotic. Five basic rules for calculating the asymptotic complexity are given. A mathematical apparatus for estimating the asymptotic complexity of a genetic algorithm is presented, which takes into account the costs of forming the initial population and performing evolution. Evolution occurs through iterations, during which generations of individuals are subjected to certain operations in order to find an optimal solution (crossing, mutation, chromosome decoding, etc.). GA, as a global search algorithm, is considered to find the optimal path without getting stuck in local minima. To assess the computational complexity of GA, we consider solving the traveling salesman problem (TSP) for 28 cities of Ukraine using a modified TSPLIB library and the DEAP platform created in the Python programming language. A block diagram of the GA is presented, the main elements of which are the tournament selection operator, the ordered crossover operator, and the inversion mutation operator. The influence of the population size and the number of generations on the asymptotic complexity of the genetic algorithm in solving the TSP problem is studied. The study considered changing the size of the GA population from 50 to 500 with a step of 50, while for each such value four sets of the number of generations were modelled: from 50 to 200 with a step of 50. Based on the obtained results, we show a linear dependence of the GA execution time on the size of the considered input data. It is shown that the smallest time complexity of the presented GA for the given TSP problem is 0.33848 seconds with a population size of 50 and a similar number of generations, while the largest value is 3.752734 seconds with a population size of 500 and a number of generations of 200. The obtained results can be used to optimise the performance of a GA in the TSP problem.

Oxoborates of the ludwigite group: Natural and mineral-like compounds as prospective materials

Research subject. Natural oxoborates of the ludwigite group, including azoproite, ludwigite, and vonsenite. Their empirical formulas based on five oxygen atoms have the following form: azoproite (Mg1.81Fe2+0.19)∑2.00(Fe3+0.36Ti0.26Mg0.26Al0.12)∑1.00 O2(BO3), ludwigite (Mg1.69Fe2+0.30Mn2+0.01)Σ2.00(Fe3+0.90Al0.07Mg0.02Sn0.01)Σ1.00O2(BO3) and vonsenite (Fe2+1.86Mg0.13)∑1.99 (Fe3+0.92Mn2+0.05Sn4+0.02Al0.02)∑1.01O2(BO3). Aim. To establish the relationship between the composition, crystal structure, and thermal behavior (293–1373 K) of the minerals. Materials and methods. Ludwigite was collected at the Iten’yurginskoe tin skarn deposit; vonsenite was collected at the Titovskoe magnesium-skarn boron deposit; azoproite was collected at magnesian skarns of the Tazheran alkaline massif. The methods of single crystal X-ray diffraction, energy dispersive X-ray spectroscopy, high-temperature X-ray diffraction, Mössbauer spectroscopy, and thermal analysis were used. Results. Low-charge cations (Fe2+, Fe2.5+, Mg2+) tend to occupy the M(1)–M(3) sites, and high-charge cations (Fe3+, Al3+, Ti4+, Sn4+) generally occupy the M(4) site. Azoproite is characterized by the highest melting temperature Tm > 1650 K. Due to the low Fe2+ content, azoproite does not undergo solid-phase decomposition across the investigated temperature range. The melting point of ludwigite exceeds 1582 K, which is due to the high Mg content; as a result of the Fe2+ → Fe3+ oxidation, it gradually decomposes with the formation of hematite, warwickite, and magnetite. The temperatures of oxidation and solid-phase decomposition in the Fe2+-rich vonsenite are approximately 100 K lower than those in ludwigite. The melting point of vonsenite is 1571 K. All the minerals are characterized by a weak degree of thermal expansion anisotropy. The main contribution to the thermal expansion anisotropy is due to the preferred orientation of the [BO3]3– triangles. Conclusions. The thermal properties of the oxoborates depend on their chemical composition. It was established that Tm increases with an increase in the Mg and Ti4+ content, and decreases with an increase in the Fe2+ content. The Fe2+ → Fe3+ oxidation is observed when the FeO component in the minerals exceeds 10 wt %, which leads to the solid-phase decomposition starting at temperatures of about 500–600 K. The values of the 293KαV volume thermal expansion of ludwigite and azoproite are comparable, while the largest values were observed for vonsenite. This is associated with the largest average bond lengths, primarily those of <Fe2+–O>6.

Regionalization of environmental and economic performances of rainwater harvesting systems

Study regionBeijing Region Study focusLimited studies have yet been done on regionalization of multi-performances of rainwater harvesting systems (RHS). In this study, the daily rainfall records from 77 stations are used, and a hydro-economic model is adopted to examine regional water saving, stormwater control and economic performances of RHS by proposing a regionalization approach. New hydrological insights for the regionHigher water saving efficiency (WSE) and reliability (R) of RHS are linked with lower water demand, larger tank size and greater rainfall conditions. Differently, higher stormwater capture efficiency (SCE) is related to higher water demand, larger tank size and lower rainfall. The WSE and R of RHS demonstrate substantial regional differences; their maximized obtainable values closely depend on water demand scenarios and range from 9% to 99%, with smaller values in western mountain area but larger values in northeast suburban and central urban areas. The maximum obtainable values of SCE range from 61% to 100%, with higher values in western mountain area, but lower values in northeast suburban and central urban areas. A 10 m3 tank size can provide the highest benefit-cost ratio of RHS across the Beijing region. The regionalization approach proposed is a useful guidance for the implementation of RHS and sustainable urban water management, and thus it has the potential for wide uses in other regions with high rainfall gradients.

The reason induced unique characteristics of local Nusselt number in straight and twisted square tubes for laminar flow

The velocity contribution and velocity gradient contribution to the transport of the heat flux defined by Fourier's law, q, are numerically investigated in this paper to investigate the reason induced the unique characteristics of Nusselt number in twisted and straight square tubes for periodically fully developed laminar flow. The reason of local Nusselt number in straight square tube at some regions is larger than that in twisted square tube are reported. It is found that the summation of velocity and its gradient contributions determines local Nusselt number under UWT. Both velocity and velocity gradient contributions are not uniformly distributed in the cross section in straight and twisted tubes. Velocity and its gradient both promote the transport of the local heat flux components along the normal direction of the wall surface which have larger values in straight square tube at some regions and result local Nusselt number has larger values. The summation contributions of velocity and its gradient are much larger in twisted square tube, especially in the region close to the wall surface. Thus the averaged heat flux components have much larger value and averaged Nusselt number in twisted square tube is larger than that in straight square tube.

LiNbO3-induced phase structure evolution and improved piezoelectric properties in BiFeO3–BaTiO3 ceramics

Eco-friendly (0.73-x)Bi1.05FeO3-xLiNbO3-0.27BaTiO3 ternary ceramics were designed and prepared via a solid-state sintering route. Based on the X-ray diffraction results and Rietveld refinement, it was found that the structure of the ceramics transformed from rhombohedral to tetragonal symmetry with the addition of LiNbO3, and at x = 0.003, there existed a morphotropic phase boundary separating the two phases. Near the phase boundary, the largest values were achieved for the piezoelectric constant d33 and planar electromechanical coupling coefficient kp, being 180 pC/N and 0.27, respectively. Due to the addition of LiNbO3, the grain size tended to become smaller. Additionally, the ceramics were transitioned from normal to relaxor ferroelectrics with increasing x. Despite the fact that the LiNbO3 addition would result in a gradual decrease of Curie temperature, a relatively high Curie temperature (535 °C) was still maintained at x = 0.003, the phase boundary composition, which also showed good temperature stability of piezoelectric properties. These experimental results can provide a reference for the practical applications of high-temperature lead-free ceramics.

Comparison of geomechanical upscaling methods for prediction of elastic modulus of heterogeneous media

Geomechanical properties of rocks are essential for understanding their elastic behavior. These parameters find their applications in various fields such as petroleum engineering, and geological storage sites, of nuclear waste and carbon dioxide and other geotechnical operations. There are several methods to obtain these parameters, including experimental methods, mathematical upscaling, and numerical simulation while experimental approaches are more trusted. The aim of this study is to estimate Young's modulus of a shale sample from several major upscaling mathematical methods and compare the results to polyaxial compressive strength test and nanoindentation measurements on the same piece of sample. To achieve this, five major theoretical upscaling models, including DEM, MT, SCA, KTF, and DM, have been utilized to calculate the Young's modulus based on constituent components of the sample that was obtained from routine XRD and geochemical analysis. The calculations for each of the five methods were performed in two scenarios: without incorporating the organic matter in the model and with it, in a range of porosity values while input parameters for each constituent components were found from the literature. Young's modulus with organic materials following the upscaling schemes was in the range of 24.0661 [GPa] to 27.0001 [GPa]. Likewise, excluding the organic substances Young’s modulus was calculated 25.1784 [GPa] and 29.1394 [GPa], as the smallest and largest values, respectively. These values were compared to the Young's modulus obtained from the nanoindentation (34.15 GPa) and polyaxial test (24.36 GPa). The Young’s modulus decreases of approximately 7% with considering organic matter around 2.45% and decrease of less than 5% with variation of 1% porosity. Based on the results, it was concluded that upscaling methods overall provide results in an acceptable range while they are more cost-effective and time-efficient when compared to expensive and time-consuming experimental approaches and can replace them. Furthermore, the use of upscaling methods reduces the need for destructive testing and also eliminates the requirement for expensive equipment with limited access to proper size of the samples and required preparations that should be followed. However, the lithology of the sample and presence of certain type of pore spaces and fractures should not be taken lightly in this process.

Intermittency of Gravity Wave Potential Energy Generated by Mountains Revealed from COSMIC-2 Observations

The intermittency of gravity wave potential energy (GWPE) in the upper troposphere and stratosphere was investigated using the Constellation Observing System for Meteorology, Ionosphere, and Climate-2 (COSMIC-2) temperature data over three typical mountains (Tibetan Plateau, Rocky Mountains, and Andes). These typical mountains have high sea level elevations but different land–sea contrast. The probability density function (PDF) of GWPE has the independent variable of GWPE and dependent variable of occurrence probability of GWPE over a region. Our analysis showed that the PDFs of GWPE over these three mountains roughly followed lognormal distributions in all heights and months. But, the key parameters (mean value and standard deviation) of lognormal distribution varied with heights and months. Above each mountain, the two key parameters exhibited similar temporal and spatial distributions. They had the largest values around the tropopause region, smaller values in the lower stratosphere (~20–30 km), and larger values in the upper stratosphere (~35–45 km). The intermittency of GWs is represented as the ratio of the GWPE at 50th percentile to the GWPE at 90th percentile. The weakest intermittency was at ~20–30 km (above the zonal mean winds of zero) over the Tibetan Plateau and Rocky Mountains in all months and over the Andes from November to March, respectively. Generally, the weakest intermittency (~0.4) occurred in the region where the key parameters were the smallest around summer. The key parameters of lognormal distribution were dominated by annual variation over the Andes throughout the height range, 8–50 km. However, the semiannual variations are also significant in the lower stratosphere over the Tibetan Plateau and Rocky Mountains. The seasonal variations in the intermittency were not as obvious as those of the key parameters. The lognormal distributions and the intermittencies derived here provide an observational constraint on the tunable parameters in GW parameterization schemes.

Experimental and simulation study on oscillating flow and heat transfer characteristics of the cooling gallery in steel pistons

To characterize the oscillating flow and heat transfer characteristics of the cooling gallery inside a steel piston, a visual experimental platform was designed and constructed. Based on experimental results, simulation models of the cooling gallery under calibration conditions were established, and the oscillating flow and heat transfer characteristics of different oil injection strategies were studied. The results show that adjusting the nozzle diameter has a more significant impact on the fluid charge ratio (FCR) of the cooling gallery compared to the injection pressure. During the reciprocating motion of the steel piston inside the cylinder, the gallery has the largest heat transfer coefficient (HTC) on the Top wall at the top dead center (TDC) and the largest value on the Bottom wall at the bottom dead center (BDC). The average HTC of the Top wall is always the largest, followed by the Bottom wall, the In wall, and the Out wall being the smallest. Compared to the original design, the average HTC of the Top, Bottom, Out, and In walls can be increased by a maximum of 4.39 %, 3.96 %, 8.01 %, and 11.80 %, respectively.

Synthesis of ultrathin hybrid membranes via the co-polymerization of acrylic acid, styrene and molybdenum disulfide and their high adsorption selectivity for lead(II) in the mixture of metal ions

Lead(II) is a potential carcinogen of heavy-metal ions (HIs). With the wide application of Pb-bearing products including lead alloy products, and new-energy lead-ion batteries, lead pollution has become a tricky problem. To solve such a difficulty, novel ultrathin MoS2-vinyl hybrid membranes (MVHMs) with a “spring” effect were synthesized via co-polymerization of acrylic acid, styrene and molybdenum disulfide (MoS2) and their adsorptions for HIs were explored. The “spring” effect derived from the interaction between the tendency of the short polyacrylic acid (PAA) chain connected with MoS2 to spread outward and the coulomb force between layers from MoS2 (s-MoS2), which enlarge the spacing of MoS2 layers without changing the number of layers after membrane formation, which changes the swelling membrane to a dense membrane and reduces the original thickness from 0.5 cm to 0.011 mm in the thickness direction. The adsorption experiment revealed that these MVHMs had super adsorption performance and high selectivity for Pb2+ by comparison with other five metal ions: Cu2+, Cd2+, Ni2+, Cr3+ and Zn2+. Especially, the adsorption quantity of MVHMs for Pb2+ could approach 2468 mg/g and the maximum adsorption ratio of qe[Pb2+]/qe[Cu2+] can reach 10.909. These values were much larger than the data obtained with the adsorbents reported in the last decade. A variety of models are applied to evaluate the effect of ionic groups. It was confirmed that –COOH plays a key role in adsorption of HIs and s-MoS2 also has a certain contribution. Conversely, ion exchange plays only a minor role during the period of adsorption process. Effective diffusion coefficient (Deff) of Pb(II) had the largest values among these metal ions. Hence, these hybrid membranes are promising adsorbents for the removal of Pb2+ from water containing various ions.

Pengaruh Leadership Style, Reward, dan Punishment terhadap Kinerja Karyawan pada PT. Hikmah Sejahtera Surabaya

PT Hikmah Sejahtera is a private company engaged in general trading. This research aims to determine how the influence of leadership style, reward, and punishment on the performance of employees of PT Hikmah Sejahtera Surabaya. The research method used in this research is a quantitative approach method with interviews, observation, documentation, and distributing questionnaires conducted by researchers in obtaining the required data. The population in this study were employees of PT Hikmah Sejahtera Surabaya, totaling 50 respondents. The analysis technique uses multiple linear regression analysis. Based on the results of this research it is concluded that the variable leadership style (X1), punishment (X3) can affect employee performance (Y) and reward (X2) has no effect on employee performance (Y). Of the three independent variables leadership style (X1), reward (X2), and punishment (X3) which have a dominant effect on the dependent variable employee performance (Y), the variable is punishment (X3) with a coefficient value of 0.327 which is the largest value among other variables.

TiO2 Nanotube Arrays Inside Ultrafine Ti Tubes with an Aspect Ratio of 2500 for Sensing Needles: The Bubble Effect in a Confined Space.

Capillary metal tubes have attracted considerable interest for flexible electronics, portable devices, trace sampling, and detection. Tailoring the microstructure and wettability inside the capillary tubes is of paramount importance, yet it presents great difficulty because of the spatial confinement. Here, the coupling effect is revealed between the fluidic and electric field induced by bubble motion in a confined space during anodic oxidation. By controlling the bubble regeneration and flow rate, uniform and superhydrophilic TiO2 nanotube arrays are developed throughout the inner surface of an ultrafine Ti tube with a diameter of 0.4mm and length of 1000mm, equivalent to an aspect ratio of 2500 that is the largest value being ever reported. The inner surface of a capillary tube is further coated with a polytetrafluoroethylene layer and explored as a sensing needle for liquid detection in terms of concentration and species. This study provides an innovative approach to tailor the microstructure and wettability in a confined space for functional capillary tubes.

Spatial relationships among offender, knife, and victim during slashing attacks: implications for crime scene reconstruction.

The offender-victim spatial relationship is crucial in reconstructing a crime scene. The study aims to evaluate the spatial relationship of performing slashing attacks on a dummy using a Chinese kitchen knife, and thus to establish a scientific basis for crime scene reconstruction. Twenty-four participants (12 males and 12 females) slashed a dummy's neck or chest using a kitchen knife, and the kinematic data were obtained using a three-dimensional motion capture system. The spatial relationships among offender, knife, and victim during slashing attacks were analyzed. Slashing distance and occupancy area are significantly influenced by gender (all P < 0.05), with males having higher values than females. Body parts significantly influence bevel angle, offender and victim azimuth angles, slashing distance, relative slashing distance, and occupancy area (all P < 0.01), with slashing the chest resulting in larger values than slashing the neck. Gender and body position significantly influence the spatial relationships of slashing action. Our data indicate that males stand farther away and occupy a larger area during slashing attacks. When the chest is slashed, the wound orientation is more diagonal, the offender's standing position and slashing distance are farther, and the occupancy area is larger compared to the neck. The findings could help identify the spatial relationships among offender, knife, and victim, providing a scientific basis for criminal investigations and court trials.

Slow response of surface water temperature to fast atmospheric variability reveals mixing heterogeneity in a deep lake

Slow and long-term variations of sea surface temperature anomalies have been interpreted as a red-noise response of the ocean surface mixed layer to fast and random atmospheric perturbations. How fast the atmospheric noise is damped depends on the mixed layer depth. In this work we apply this theory to determine the relevant spatial and temporal scales of surface layer thermal inertia in lakes. We fit a first order auto-regressive model to the satellite-derived Lake Surface Water Temperature (LSWT) anomalies in Lake Garda, Italy. The fit provides a time scale, from which we determine the mixed layer depth. The obtained result shows a clear spatial pattern resembling the morphological features of the lake, with larger values (7.18± 0.3 m) in the deeper northwestern basin, and smaller values (3.18 ± 0.24 m) in the southern shallower basin. Such variations are confirmed by in-situ measurements in three monitoring points in the lake and connect to the first Empirical Orthogonal Function of satellite-derived LSWT and chlorophyll-a concentration. Evidence from our case study open a new perspective for interpreting lake-atmosphere interactions and confirm that remotely sensed variables, typically associated with properties of the surface layers, also carry information on the relevant spatial and temporal scales of mixed-layer processes.

Stress-strain states of reinforced concrete spans of a railroad overpass using a spatial finite element model

The paper presents the results of computational analysis of the stress-strain state of reinforced concrete spans of the railway (single-track railway line) overpass over the highway, under specified loads using spatial finite element models. The static load consists of a cohesion of three TEM-18 diesel locomotives and two loaded gondola cars (up to 25 tons per axle). The purpose of this study was to ensure reliable and safe operation of artificial structures on the railroads, as there is a constant increase in transit freight trains from China through the territory of Kazakhstan to near and far abroad, and often the load on the axle reaches 25 tons, and sometimes larger values – up to 27 tons per axle. The results of the study are recommended to be used for inspections and tests of typical girder bridge spans, as well as in the case of monitoring their technical condition with increasing operational loads.

Experimental and numerical failure mechanism evaluation of anisotropic rocks using extended finite element method

Rocks often show an anisotropic behavior due to microcracks, mineral-based structure, and unequal in-situ stresses. The crack tip's stress intensity factors (SIFs) that control rock failure heavily depend on anisotropy. Given the significance of extensive research to identify the effects of anisotropy on the mechanical behavior and strength of rocks, numerical modeling is considered an essential method in designing structures and analyzing their stability. This study experimentally and numerically evaluated the effects of the bedding angle, initial crack angle with the loading axis, crack length, and anisotropy ratio on the stress intensity factor of transversely isotropic rocks via the extended finite element method (XFEM). Cracked chevron-notched Brazilian disks (CCNBDs) were fabricated from phyllite under the International Society for Rock Mechanics (ISRM) standards and tested at different initial crack lengths and angles for validation. The XFEM approach was then used to predict toughness and crack propagation path in the tested and new specimens with varying ratios of anisotropy and bedding angles (ψ = 0, 30, 45, 60, and 90°). The results demonstrated that with the increase of the anisotropy ratio, in equal crack length and initial angle, the absolute value of the SIFs have larger values. In addition, with the increase of crack length, the first and second modes of SIF increased, which indicates the failure of the specimen at lower loads. Also, bedding angle is effective on the stress intensity factors and this effect becomes more intense as the crack length increases. Finally, the anisotropy properties not only affect the values of SIFs, but also can change the angle at which the specimen experiences pure mode I or mode II.