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To investigate the dynamic compression properties and crushing features of gas-containing coal under complex geological environments, a dynamic and static combined loading test system was independently developed for conducting triaxial dynamic compression tests. The dynamic stress-strain curves under different strain rates were analyzed to study the effects of strain rate and gas pressure on the dynamic mechanical characteristics. Crushed coal samples were sieved and analyzed using a standard sieve and fractal theory. The study reveals that strain rate and gas pressure significantly influence the plastic deformation stage of the dynamic stress-strain curve of gas-containing coal. Under high strain rates, low gas pressure lengthens the plastic deformation stage, while high gas pressure shortens this stage and enhances brittleness. Increased strain rates lead to higher peak stress and peak strain in gas-containing coal samples. As gas pressure increases, the dynamic peak stress decreases, and the peak strain initially increases and then decreases. The damage form of gas-containing coal is primarily tensile-shear, accompanied by crushing damage. The fractal dimension increases at higher gas pressures and strain rates but stabilizes at gas pressures greater than 0.7 MPa. These findings enhance the understanding of the dynamic behavior of gas-containing coal under triaxial loading and provide valuable insights for the prevention and control of dynamic hazards in gas-containing coal bodies under complex stress environments. [ABSTRACT FROM AUTHOR]

Silica fume (SF) has been widely used in engineering; however, its densification during transportation reduces its original pozzolanic activity. This paper investigates the effects of wet grinding and chemical activation on the mechanical properties and hydration products of silica fume in cement-based materials, revealing the mechanism by which wet grinding improves these properties. The results indicate that wet grinding effectively reduces the particle size of silica fume. Under optimal excitation conditions (250 r/min, 20 min), the median particle size is reduced to 12.1 μm, 2.27 times smaller than before excitation. The 28-day compressive strength of the silica fume cement paste reaches 60.8 MPa, 23.7% higher than that of the reference group. This approach effectively mitigates nano-agglomeration, enhances the pozzolanic activity of silica fume, and promotes AFt and C-S-H gel formation. The findings demonstrate that wet grinding activation can further enhance the utilization rate of silica fume. [ABSTRACT FROM AUTHOR]

This study reports an alkali-activated binder including blast furnace slag (BFS) together with marble waste (MW). Cement is an industrial product that emits a significant amount of CO2 during its production and incurs high energy costs. MW is generated during the extraction, cutting, and processing of marble in production facilities, where dust mixes with water to form a settling sludge. This sludge is an environmentally harmful waste that must be disposed of in accordance with legal regulations. In this study, a substantial amount of MW, a by-product with considerable environmental and economic impacts worldwide, was utilized in the production of a binder through the alkaline activation of BFS. In doing this, different experimental parameters were tested to obtain the best binder samples according to workability and mechanical properties. Then, some experiments such as drying shrinkage determination, strength testing, and microstructure analyses were fulfilled through samples with the best values. The findings supported the improvement of the rapid-setting property of BFS by means of the addition of MW. MW reduced the time-dependent drying shrinkage values of BFS by 55%, especially in slag alkaline activation systems with a low or moderate alkali activator content. The substitution of MW (≤50%) in BFS increased flexural and compressive strengths (4.5 and 61.7 MPa), while a reference sample contained BFS only. Although the use of MW did not create a new phase, it contributed to a C-S-H bonding structure during the alkali activation of BFS in a microstructure analysis. [ABSTRACT FROM AUTHOR]

Abstract To investigate the dynamic compression properties and crushing features of gas-containing coal under complex geological environments, a dynamic and static combined loading test system was independently developed for conducting triaxial dynamic compression tests. The dynamic stress-strain curves under different strain rates were analyzed to study the effects of strain rate and gas pressure on the dynamic mechanical characteristics. Crushed coal samples were sieved and analyzed using a standard sieve and fractal theory. The study reveals that strain rate and gas pressure significantly influence the plastic deformation stage of the dynamic stress-strain curve of gas-containing coal. Under high strain rates, low gas pressure lengthens the plastic deformation stage, while high gas pressure shortens this stage and enhances brittleness. Increased strain rates lead to higher peak stress and peak strain in gas-containing coal samples. As gas pressure increases, the dynamic peak stress decreases, and the peak strain initially increases and then decreases. The damage form of gas-containing coal is primarily tensile-shear, accompanied by crushing damage. The fractal dimension increases at higher gas pressures and strain rates but stabilizes at gas pressures greater than 0.7 MPa. These findings enhance the understanding of the dynamic behavior of gas-containing coal under triaxial loading and provide valuable insights for the prevention and control of dynamic hazards in gas-containing coal bodies under complex stress environments.

Objective: This study aims to explore the mechanical differences in executing the basic WALK step of the rumba from a kinematic perspective between professional dancers and amateur students, thereby guiding the teaching and training of the WALK step. Methods: Five professional dancers and five amateur students participated in video recordings using two JVC cameras. Kinematic data were processed using APAS software to analyze the center of gravity changes and lower limb joint data in both groups. Results: The movement time of the center of gravity showed no significant difference between the professional dancers and amateur students at different stages of the complete WALK step (p > 0.05). Center of gravity displacements were similar on the X-axis, but significant differences were observed on the Y and Z axes (p < 0.05). In lower limb kinematics, the amateur group exhibited notable variations in hip and knee flexion and extension in the sagittal plane compared to the professional group. Peak hip flexion and extension angles were 51.26 +/- 4.45° and -11.33 +/- 0.91°, respectively, in the amateur group, both smaller than those in the professional group (p < 0.05). Additionally, the peak knee adduction angle in the frontal plane was -4.64 +/- 5.65°, significantly smaller than that of the professional group (p < 0.05). The amateur group also demonstrated significant differences from the professional group in hip internal and external rotation, knee internal rotation, and ankle external rotation in the horizontal plane. Conclusion: The amateur group exhibits insufficient hip twisting and weak joint control during the execution of WALK steps, making them more susceptible to sports injuries. Strengthening lower limb muscle groups and improving overall body stability are recommended for this group.

Due to its high effectiveness and low cost, viscoelastic damper (VED) is a commonly used type of passive energy dissipation device to reduce structural vibrations and responses against earthquakes and strong winds. Over the past decades, scholars have developed new types of VEDs to be installed at different structural locations. These VEDs offer better post-disaster recoverability and smarter behaviors for structures. Nonetheless, existing efforts of various VEDs and the technologies supporting VEDs were seldomly summarized. This article presents a critical state-of-art review of the existing research on VEDs, hybrid VED devices, and the design methods for structures installed with VEDs. First, the VEDs are classified based on the design locations in building structures, including VEDs used as coupling beams and damping walls, installed in braces and beam-column joints, and used to connect parallel structures. In addition to these classic VEDs, the study presents the high-performance VEDs and the corresponding techniques, such as the combined usage with other materials and/or devices. Furthermore, as an important contribution to the presented work, various design methods for structures enhanced by VEDs were systematically summarized. These methods considered different evaluation parameters aiming at different design targets. Finally, this article identifies and highlights research challenges in the existing studies. Possible improvements that could be made in the future were also provided. [ABSTRACT FROM AUTHOR]

In this paper, a steady-state and dynamic response model is proposed to predict the working characteristics of the electromechanical transmission system including eddy-current magnetic couplers. Considering the influence of mechanical characteristics of motor and load device on the performance of eddy-current magnetic couplers, the system is divided into input and output for kinematic analysis. The expressions of electromagnetic torque versus speed are obtained through layer analysis of the eddy-current magnetic coupler during steady-state and then, the dynamic response model of the system is established by combining the kinematic analysis with the motor, the eddy-current magnetic coupler and three typical loads (constant torque load, quadratic rate load and constant power load). The dynamic characteristics during starting and speed-regulation of the system under constant torque loads are analyzed using the proposed model. The variations of the torque and speed with time of input and output are calculated by numerical integration. Finally, the speed and torque during starting and speed-regulation computed with the dynamic response model are compared with those obtained from the experimental results. The result shows a good agreement. [ABSTRACT FROM AUTHOR]

In recent decades, there have been initiatives to incorporate carbon nanomaterials (CNMs) into cement composites, particularly graphene oxide (GO), carbon nanotubes, graphite (GP), and mild carbon (MC). Nevertheless, little is known about how these CNMs interact with the cement matrix itself. In this research, the impact of CNM incorporation at high temperatures (250, 500, 750, and 1,000°C) on cement’s mechanical characteristics and microstructure was investigated. Nine mixes were created with the CNM content (0.1 and 0.3%) being taken into consideration. The microstructure of the CNM composites was further investigated using X-ray diffractometry, thermogravimetry, derivative thermogravimetry, digital microscopy, and micro-computed tomography (micro-CT). Based on research observations, the study demonstrated that the mechanical properties of most specimens could be enhanced through the introduction of CNMs. The recommended proportions of GP-0.1, GO-0.1, and MC-0.1, in accordance with the weight of the binder, and the impact of the CNMs on the elastic modulus were also assessed. As a consequence, the CNM’s porous structure and apparent crack pattern were identified using microstructure analysis.

Physical simulation test is an effective method of occurrence mechanism and prevention and control of coal mine gas disasters. At present, the mechanical strength and permeability of briquette materials used in coal mine gas disasters physical simulation test are very different from that of raw coal. How improve the compressive strength and permeability of the briquette coal（BC） is the key problem in the briquette forming process. Based on this, several secondary carbonized briquettes with different holding time were made by a hot pressing method in this paper, and SEM, NMR, XRD, FTIR, MTS-815 rock mechanics test system and gas-containing coal thermal-fluid-solid coupling triaxial servo seepage test device were used to test and analyze secondary carbonized briquettes with different holding times. The effects of different holding times on microcrystalline structural parameters, basic structural units of aromatic hydrocarbons, alkyl side chains and various functional groups, surface morphology, T2 spectral morphology, and porosity evolution were analyzed, the mechanical and seepage characteristics of secondary carbonized briquet under different holding times were clarified. and the optimal holding time was determined. The results show that the surface roughness and pore diameter of the secondary carbonized briquette gradually increase with the increases of holding time, and cracks appear on the surface of BC after increasing to 6.7 h. The longer holding time, the more obvious cracks are. BC cumulative porosity and mesoporous porosity increased gradually, while microporous porosity decreased gradually. The aromatic layer spacing (d002) decreased first and then increased, while the microcrystalline diameter (La) and microcrystalline height (Lc) increased first and then decreased. The length of fatty chain decreased, and the degree of condensation of aromatic ring (Aar/Aal) increased first and then decreased. The uniaxial compressive strength increases first and then decreases, and the permeability decreases first and then increases. When the holding time is 5.3 h, the optimal holding time is obtained. In this case, the uniaxial compressive strength and elastic modulus of hot pressing BC are the largest, Poisson's ratio and permeability are the smallest, and its mechanical strength, permeability and density are 9.85 MPa, 1.49 × 10−15 m2, and 1.127 g/cm3, respectively. This study has important practical guiding significance for improving the real reducibility of the occurrence mechanism and prevention and control basic test of coal mine gas disaster and effectively preventing and controlling coal mine gas disaster accidents.

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The coal and gas outburst and rockburst coupling disaster is becoming increasingly serious due to deep mining. To clarify the mechanism inducing the outburst–rockburst coupling disaster, a true triaxial single-sided unloading mechanical test was conducted with the aid of a true triaxial solid–thermal–gas coupling test device, an industrial computed tomography (CT) system, and an acoustic emission system. Through this test, the mechanical characteristics, meso crushing characteristics, and acoustic characteristics in the disaster formation process were obtained. Additionally, the outburst–rockburst coupling instability disaster law was verified by numerical simulation. The results demonstrated that the stress unloading degree of the coal body was negatively correlated with the initial gas pressure in the outburst–rockburst coupling disaster. The time domain parameter count and energy of acoustic emission exhibited a "bimodal" distribution pattern in the instability stage. The rockburst would occur when the peak value was in a "low-count and high-energy" state, while coal and gas outburst would occur when the peak value was in a "high-count and low-energy" state. The meso slice revealed that gas degradation promoted the development of microcracks in the coal body, and the penetration of cracks resulted in the main cracks of structural instability during rockburst. The coal and gas outburst was mainly attributed to the "cross" shear failure pattern of the coal body. These research findings may lay a foundation for the effective prevention and control of outburst–rockburst coupling disasters. [ABSTRACT FROM AUTHOR]

Silica fume (SF) has been widely used in engineering; however, its densification during transportation reduces its original pozzolanic activity. This paper investigates the effects of wet grinding and chemical activation on the mechanical properties and hydration products of silica fume in cement-based materials, revealing the mechanism by which wet grinding improves these properties. The results indicate that wet grinding effectively reduces the particle size of silica fume. Under optimal excitation conditions (250 r/min, 20 min), the median particle size is reduced to 12.1 μm, 2.27 times smaller than before excitation. The 28-day compressive strength of the silica fume cement paste reaches 60.8 MPa, 23.7% higher than that of the reference group. This approach effectively mitigates nano-agglomeration, enhances the pozzolanic activity of silica fume, and promotes AFt and C-S-H gel formation. The findings demonstrate that wet grinding activation can further enhance the utilization rate of silica fume.

Copyright of Journal of Architecture & Civil Engineering is the property of Chang'an Daxue Zazhishe and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Aiming at the problem that the guide mechanism of arc-shaped self-floating anti-collision device is prone to plastic deformation during daily operation, the hydrodynamic analysis model of arc-shaped self-floating lifting anti-collision device based on three-dimensional potential flow theory has been established to analyze the motion response and mechanical characteristics under the combination of different incident angle of wave and flow. The results show that the continuous action of water flow is beneficial to reduce the motion response of the anti-collision device. The high stiffness of the guide mechanism on the downstream side leads to a greater force while other guide mechanisms have no force or have little force. The wave incidence angle has great influence on the force of guiding mechanism. When the Angle between the wave incidence angle and the flow direction is small, the superposition effect of the wave current will increase, the guiding mechanism on the downstream side will lead to a steep increase in the axial force. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the potential of Spirulina platensis (SP), a high protein content microalgae species, to be used as feedstock for a new type of solid biofuel technology, namely bio-coke. The SP bio-coke production was conducted at different formation temperatures of 130, 150 and 170 °C without any binder. The results showed that SP BIC 150, which was produced at the optimum formation temperature of 150 °C, exhibited the highest density and mechanical strength when compared with that of SP BIC 130 and SP BIC 170. This means that it strongly influenced its stable structure during the combustion process. With the strong structure of SP BIC 150, the breakdown of bio-coke can be prevented during flame combustion, thereby contributing to a longer char and total combustion time. The conversion of SP microalgae showed good potential to be used as an alternative renewable energy source in the future.

Purpose. Presentation of the results of modeling and practical implementation of a magnetoelectric converter for hydraulics and pneumatics systems of the aerospace industry. Methodology. Calculations of three-dimensional magnetic fields are carried out with the Finite Element Method by JMAG program. The solution of the differential equations connecting the input voltage, current, magnetic flux and torque is performed by numerical integration. Results. As a result of calculations, the converter configuration was obtained. Tests of the prototype model of the converter confirmed the principle workability of the adopted design and design solutions in its development. Practical value. Tests of the converter prototype sample confirmed the fundamental performance of the adopted design and constructive solutions.

A sodium-cooled fast reactor (SFR) considers adopting 3-dimensional seismic isolation devices for withstanding seismic loads not only horizontal but also vertical direction. A seismic isolation device consists of a laminated rubber bearing and horizontal oil dampers for horizontal direction, coned disc springs and vertical oil dampers for vertical direction, respectively. And also, in order to make horizontal and vertical motion independent, sliding elements are adopted. In order to investigate the performance of each component and the feasibility of integrated system for SFR, the experiments such as load-displacement tests, vibrating tests, etc., to each component of seismic isolation devices and seismic response analysis are carried out. As those experimental results, the mechanical characteristics of each component and the devices are grasped, then it is demonstrated that components and devices have expected performances to reduce the seismic loading within the design range. As the analytical results of seismic response, it is indicated that this 3-dimesional seismic isolation device and system can reduce the seismic response on horizontal and vertical simultaneously. Based on the analytical studies and experimental results, the feasibility of newly developed 3-dimensional seismic isolation system is obtained and the prospect of practical application of 3D seismic isolation system for fast reactor is implied in this paper.

In the field of rock engineering, complexity of stress environment is an important factor affecting its stability. Thus, in view of fracture mechanism of rock under different loading rates within the scope of quasi-static strain rate, four groups of uniaxial compression tests with different strain rates were carried out on sandstone specimens, and strength, deformation, failure modes and acoustic emission characteristics of specimens were compared and analyzed. Furthermore, the fracture mechanism was discussed from the perspective of fracture characteristics based on fractal dimension, crack propagation law inverted through acoustic emission b-value, and micro fracture morphology. The results showed that as the strain rate increased from 10 to 5 s-1 to 10-2 s-1, the fractal dimension of rock fragments increased, and the fractal dimension of rock fragments increased by 9.66%, 7.32%, and 3.77% successively for every 10 times increase in strain rate, which means that the equivalent size of fragments was getting smaller, and the fragmentation feature was becoming increasingly prominent. The crack propagation process based on acoustic emission b-value showed that with the increase of loading rate, the specimen entered the rapid crack propagation stage earlier, in order of 68%, 66%, 29%, and 22% of peak stress. Moreover, the microscopic fracture morphology showed that with the increase of loading rate, transgranular phenomenon was clear, and the fracture morphology changed from smooth to rough. That meant that the fracture of sandstone rock at high loading rates was mainly caused by the propagation of large cracks, which was different from the slow process of initiation, convergence and re-propagation of small cracks at low strain rates. Due to warm and humid air currents of the Indian Ocean and the southwest monsoon, the Palong Zangbo catchment in southeastern Tibet has developed oceanic glaciers in the valley, and the activity of glacial debris flows has been gradually intensified under neotectonic activity, frequent earthquakes, climate change, and extreme rainfall. In this paper, the topographic and morphological data of the debris flow basin, the dynamic evolution characteristics of glaciers and glacial lakes were analyzed by using multisource long-term series of remote sensing images. Simultaneously, the distribution of moraines and landslide sources were extracted based on satellite image. In addition, climate change in the study area was analysed using temperature and rainfall data from the last 40 years, revealing that the average temperature in the study area from May to October presented a fluctuating tendency as a whole, especially after 2013, when the temperature gradually increased. As these temperature changes led to continuous melting of the glaciers in the study area, the glacier area decreased from 8,300 km2 in 1988-4,584 km2 in 2019, which decreased nearly 45%. However, the number and area of glacial lakes in the study area gradually increased under a power-law trend, which further led to a significant increase on the possibility of glacial lake rupture in the study area. Due to the joint effects of earthquakes, glacier melting and glacial lake collapse, the debris flows in the study area were well developed, and a total of 122 debris flows were found with varying channel lengths, areas and material sources. Importantly, the characteristics of the glaciers, glacial lakes and climate change in the study area have indicated that the glaciers have retreated, the number of glacial lakes has increased, and the risk of debris flow in this basin will increase in the future. Therefore, it is necessary to strengthen monitoring and early warnings on floods due to glacial lake collapses and debris flows in the study area to improve the risk management of debris flows and floods and the prevention and mitigation of disasters. [ABSTRACT FROM AUTHOR]

Due to increasing awareness of the indoor environmental quality, efforts to maintain human indoor thermal comfort have been intensely carried out worldwide in recent decades. Particularly, thermal insulating materials with good mechanical performance are of great interest to suit this functionality. In this respect, construction materials should be able to impede heat transfer while achieving the required mechanical strength. Silica aerogel (SA) is attractive to fit these criteria due to its favorable characteristics such as low thermal conductivity, lightweight, and sustainability. Therefore, the present work studies the mechanical properties of both mortar with sand replaced by silica aerogel and sandwiched mortar with silica aerogel mat core. First, the optimal mix design was determined for the mortars with 0%, 15%, 20%, and 25% sand replaced by volume with silica aerogel through compressive strength on Days 7 and 28. Flexural strength and modulus of elasticity were also assessed. In terms of sandwiched mortar with silica aerogel mat core, both edgewise and flatwise compressive characteristics were examined for 9-, 12-, and 15-mm core thicknesses. Additionally, the optimal parameters of both specimen types were linked to their microstructures and failure modes. According to the result, 15% by volume of silica aerogel (by replacing sand) was determined as the optimum ratio for the SA powder mortar. Meanwhile, for silica aerogel sandwiched mortar, samples with 15- and 12-mm core thicknesses achieved the highest flatwise and edgewise compressive strengths, respectively. [ABSTRACT FROM AUTHOR]

The backfill materials are often subject to external dynamic disturbances such as blasting and drilling when playing a supporting role, which seriously endangers the mining safety, and the length of maintenance time will also affect the mining efficiency of the mine. Therefore, the Separated Hopkinson Pressure Bar (SHPB) system is used to study the dynamic characteristics of cemented tailings backfill materials of different ages, and LS - DYNA finite ele- ment software is used to numerically simulate the stress strain characteristics of samples under dynamic impact. The results show that under dynamic impact, the samples aged 28 d have a shorter compaction stage and a longer linear elastic stage than the samples aged 3 d, and the post-peak strength decreases significantly. The dynamic strength of the 2 samples is basically positively correlated with the strain rate. The simulation results show that there is a large stress concentration area on the side near the transmission end of the sample at the age of 3 d, and the strain is generated and extends uniformly to the incident end. The stress concentration zone and strain of the sample at 28 d of age mainly appeared in the lateral axial direction and gradually ran through the whole sample. The simulation results are consistent with the crack propagation captured by high-speed photography, and the research results can provide some theoretical reference for determining a reasonable mining time for underground mines. [ABSTRACT FROM AUTHOR]

The development of a computational model of an induction motor with ring windings (IMRWs) for processing of nuclear waste is considered. At the first stage of the work, the overload capacity of the computational model of an IMRW was analyzed using the finite element method, the calculation being carried out in stages, taking into account the production and physical features of the IMRW prototype design. The IMRW model takes into account the influence of the oxide film on stator core sheets, technological gaps, eddy currents, and temperature conditions of the stator and rotor windings on the overload capacity of the IMRW. At the second stage, the mechanical characteristics of the IMRW were analytically calculated in the Ansys program using the parameters of the equivalent circuit determined by analyzing the design model of the motor. The calculated mechanical characteristics of an IMRW obtained by the finite element method and analytical calculation are compared with the results of testing the prototype. [ABSTRACT FROM AUTHOR]

Purpose. Presentation of the results of modeling and practical implementation of a magnetoelectric converter for hydraulics and pneumatics systems of the aerospace industry. Methodology. Calculations of three-dimensional magnetic fields are carried out with the Finite Element Method by JMAG program. The solution of the differential equations connecting the input voltage, current, magnetic flux and torque is performed by numerical integration. Results. As a result of calculations, the converter configuration was obtained. Tests of the prototype model of the converter confirmed the principle workability of the adopted design and design solutions in its development. Practical value. Tests of the converter prototype sample confirmed the fundamental performance of the adopted design and constructive solutions. [ABSTRACT FROM AUTHOR]

The coal and gas outburst and rockburst coupling disaster is becoming increasingly serious due to deep mining. To clarify the mechanism inducing the outburst–rockburst coupling disaster, a true triaxial single-sided unloading mechanical test was conducted with the aid of a true triaxial solid–thermal–gas coupling test device, an industrial computed tomography (CT) system, and an acoustic emission system. Through this test, the mechanical characteristics, meso crushing characteristics, and acoustic characteristics in the disaster formation process were obtained. Additionally, the outburst–rockburst coupling instability disaster law was verified by numerical simulation. The results demonstrated that the stress unloading degree of the coal body was negatively correlated with the initial gas pressure in the outburst–rockburst coupling disaster. The time domain parameter count and energy of acoustic emission exhibited a “bimodal” distribution pattern in the instability stage. The rockburst would occur when the peak value was in a “low-count and high-energy” state, while coal and gas outburst would occur when the peak value was in a “high-count and low-energy” state. The meso slice revealed that gas degradation promoted the development of microcracks in the coal body, and the penetration of cracks resulted in the main cracks of structural instability during rockburst. The coal and gas outburst was mainly attributed to the “cross” shear failure pattern of the coal body. These research findings may lay a foundation for the effective prevention and control of outburst–rockburst coupling disasters.

In the field of rock engineering, complexity of stress environment is an important factor affecting its stability. Thus, in view of fracture mechanism of rock under different loading rates within the scope of quasi-static strain rate, four groups of uniaxial compression tests with different strain rates were carried out on sandstone specimens, and strength, deformation, failure modes and acoustic emission characteristics of specimens were compared and analyzed. Furthermore, the fracture mechanism was discussed from the perspective of fracture characteristics based on fractal dimension, crack propagation law inverted through acoustic emission b-value, and micro fracture morphology. The results showed that as the strain rate increased from 10 to 5 s−1 to 10−2 s−1, the fractal dimension of rock fragments increased, and the fractal dimension of rock fragments increased by 9.66%, 7.32%, and 3.77% successively for every 10 times increase in strain rate, which means that the equivalent size of fragments was getting smaller, and the fragmentation feature was becoming increasingly prominent. The crack propagation process based on acoustic emission b-value showed that with the increase of loading rate, the specimen entered the rapid crack propagation stage earlier, in order of 68%, 66%, 29%, and 22% of peak stress. Moreover, the microscopic fracture morphology showed that with the increase of loading rate, transgranular phenomenon was clear, and the fracture morphology changed from smooth to rough. That meant that the fracture of sandstone rock at high loading rates was mainly caused by the propagation of large cracks, which was different from the slow process of initiation, convergence and re-propagation of small cracks at low strain rates.

The task of ensuring smooth movement of the conveyor belt during the operation of powerful belt conveyors with a long route and several intermediate electric drives is an urgent technical problem. One of the effective ways to solve this problem is to create drives that ensure the joint operation of an electric motor and a hydraulic coupling. In this article, a mathematical model of the joint operation of an electric motor and a hydraulic coupling is proposed. When constructing the mechanical characteristics of their joint work, possible deviations of the electric motor slip from the nominal values are taken into account. To simulate various possible approximating functions that describe the mechanical characteristics of the drive, two of the most accurate mathematical expressions that are used are the Kloss equation and the equation for interpolating hyperbolic functions. With regard to the electric drive of a powerful belt conveyor, the analysis of the appropriate areas of application of these dependencies is carried out, their main advantages and disadvantages are considered. [ABSTRACT FROM AUTHOR]

This paper focuses on the development of high-flowability liquefied stabilized soils (HFLSS) made of recycled construction sludge (RCS) to enhance their application in construction work. Liquefied stabilized soils (LSSs) have already found widespread use in construction sites, particularly for filling long-distance structures and dealing with complex underground spaces. However, to further optimize their performance, the development of high-flowability liquefied stabilized soils (HFLSSs) with superior flowability is required. This study experimentally investigates the basic properties, including mechanical characteristics and flowability performance, of the newly developed HFLSS made of RCS. The results confirm that the developed HFLSS made of RCS meets the quality requirements expected from LSSs and exhibits enhanced flowability, making it a promising material for construction applications. The advanced development of LSSs in this paper expects to promote recycling construction-generated soils, including construction-generated sludges in the construction industry. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Mechanical Strength / Jixie Qiangdu is the property of Zhengzhou Research Institute of Mechanical Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Safety protection design is a key problem to be considered in structural design. The study on mechanical characteristics of rolling lobe air spring（RLAS） under the extreme working condition lays an important foundation for its safety protection design. Considering the influence of outer diameter of rubber bellows along with the height of air spring, taking the radius of arc segment and inner cone angle of linear segment as the key design parameters, a novel mechanical model of rolling lobe air spring with safety protection design is established. The experimental results show that the maximum relative error of structural parameters of rolling lobe air spring is 11.9%, the relative error of static stiffness under different pressure in the extreme condition is less than 11% and the maximum relative error of load capacity is less than 6%, which all proves the correctness of mechanical model of RLAS. Force gain and stiffness gain are further proposed as quantitative characterization indexes of safety protection design, and the influence laws of key design parameters on mechanical characteristics and quantitative characterization indexes of rolling lob air spring under extreme condition are explored. The research results provide theoretical support for accurate calculation of safety protection capability of RLAS in the design stage.

In order to solve the problem of calculating the air gap magnetic field and torque of slotted-type magnetic couplers, a subdomain analysis model is introduced. The magnetic couplers are divided into five regions along the axis, the boundary equations are established at the interfaces of each region. According to the alternating arrangement characteristics of yoke teeth and the conductor and the vector magnetic potential formulas in yoke teeth and the copper conductor disk are deduced respectively. Due to the end effect, Schwarz-Christoffel mapping is used to modify the coefficient of the flux density at the end face of the cogging. On the basis of obtaining the vector magnetic potential of the yoke iron and conductor respectively, the formulas of the air gap magnetic field and electromagnetic torque are deduced. The structure parameters of the slotted-type magnetic couplers are substituted into the theoretical model to calculate the axial air-gap magnetic field distribution and mechanical characteristic curves. By comparing the results with those obtained by finite element simulation, the accuracy of the theoretical model is verified and the cause of the error is analyzed.

The use of natural fiber to develop bio-composites has a low impact on the environment because of its renewable resources and biodegradability. This work investigated the feasibility of producing bio-composites of natural hemp fiber (hemp)-filled biopolymer polylactic acid (PLA). A high blend ratio of hemp (up to 30 wt%) was successfully achieved in a scaling up process. This production process was further verified by blending hemp with different PLA types and the mechanical properties of the obtained bio-composites showed repeatable results. In addition, the PLA/hemp composites showed comparable tensile strength as neat PLA (~50 MPa, depending on the PLA types) and a faster degradation ratio than neat PLA. This work provides a scalable, convenient and cost-effective approach to produce high-quality PLA/hemp bio-composites, which paves the way for scaling-up commercial production of PLA/hemp bio-composites toward practical applications.

By virtue of a great progress of semiconductor fabrication technologies, micro electro‐mechanical systems (MEMS) have been developed for a wide variety of industries. For reliability of MEMS, micromaterials in MEMS need to be examined experimentally, and the obtained results need to be reflected in the design of MEMS. In addition, with the benefit of such the MEMS technology, nowadays mechanical characteristics of nanomaterials have been evaluated precisely. Nanoscale mechanical testing provides an opportunity to find new unique physical phenomena, such as plastic deformation in Si at intermediate temperatures. In this review paper, mechanical testing technologies developed for investigating micro and nanoscale materials are reviewed. Then, mechanical characteristics of Si and other materials evaluated using the micro and nano mechanical testing technologies are introduced. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Cyclical impact loads will transform into low-frequency fatigue loads during propagation and will induce creep deformation of far-field rock under long-term disturbance loads. Laboratory tests of specimens under different fatigue shear loads were conducted. The mechanical responses and creep laws of the specimen were analyzed in detail. Based on the experimental results, a new constitutive model was explored. The results reveal that the stress‒strain curves of the specimen show a trend of step-path increasing under stable and fatigue load circularly. With an increase in fatigue load, the shear strength and elastic modulus of the specimens decrease gradually, while the corresponding failure strain increases gradually. The damage index composed of peak time and peak shear stress can reflect the failure of rock under fatigue loading, and the fatigue amplitude has the greatest influence on specimen deterioration. A fatigue stage in the shear creep curve occurs and is caused by the fatigue load. The fatigue creep rate increases gradually as the fatigue parameter increases. A combined nonlinear damage creep model based on the Nishihara model, elastic body, nonlinear creep body, and fatigue damage function (termed the NENF model), describing the creep responses of rock, anchor, accelerated creep, and fatigue load, respectively, was established. Compared with test data, the creep equation of the model has good accuracy in describing the whole shear creep process of specimens under fatigue loading and provides a new framework for the stability of anchoring rock masses. In this study, an experimental study on the mechanical responses of marble under different fatigue loads was conducted using a servo-controlled compression shear test machine equipped with an improved fixture system. The mechanical responses and creep laws of the specimen were analyzed in great detail. Based on the experimental results, a combined Nishihara model, elastic body, nonlinear creep body, and fatigue damage function (NENF) model describing the whole process of shear creep in an anchored joint rock mass (AJRM) under fatigue load was established. Compared with test data, the creep equation of the model has a good accuracy in describing the whole shear creep process of the specimen under the combination of stable load and fatigue load. This study provides the theoretical basis for the understanding of the long-term stability in AJRM. [ABSTRACT FROM AUTHOR]

Although the current ecological engineering technology can reinforce shallow landslides, it cannot reinforce deep landslides. A new type of ecological engineering technology-living tree stump slope protection was developed, aiming at the deficiency of current ecological engineering technology. For living stumps with different tap root lengths, the mechanical properties of the living stump slope and root system were analyzed. The model was based on the finite element method, using the Mohr-Coulomb failure criterion to consider the mechanical plasticity of the soil. The three-dimensional (3D) models of living stumps with different tap root lengths were simulated by embedded beam elements. Changes in stress and strain of soil and root system were simulated. The strength reduction method was used here to calculate the safety factor of the slope. The results showed that long taproots moved the soil shear stress area to deeper soil layers, increasing the stability of the slope. The root system in the middle and lower part of the slope mainly exerted its tensile strength and played a positive role in the stability of the slope. The longer the taproots, the more stable the slope. Slope stability may be affected by root length, spatial root morphology, and the spatial layout of the root system on the slope. Planting living stumps in the middle and lower part of the slope densely was recommended in ecological engineering. [ABSTRACT FROM AUTHOR]

Recently, increasing attention has been paid to sheet joining process for building lightweight structures. Clinching technology is an energy-saving and cost-efficient green joining method. The main factor affecting the development of conventional clinching using round punch is the unsatisfactory joint strength. To improve the mechanical properties of clinched joints, the tools and process parameters of the clinching process need to be optimized. In the study, the influence of forming forces on joining quality of clinched joints using a stepped punch was investigated using experimental methods. The geometrical parameter, failure mode, mechanical characteristic and energy absorption were analyzed in detail. From comparing the clinched joints created with a round punch, it can be concluded that the usage of stepped punch is meaningful to create joints with higher neck thickness. At the same forming force, the maximum increment in tensile and shear strength of the joints created by the stepped punch was 26.1% and 59.2%, respectively.

Tyres are the sole vehicle components in direct contact with the ground, so making an accurate description of their ground pressure distribution is crucial for studying tyres and vehicles mechanical characteristics. The incorporation of an insert body on the rim leads to a significant divergence in the ground pressure distribution of inserts supporting run-flat tyre (ISRFT) under zero-pressure conditions compared to radial tyres. To elucidate the ground pressure distribution law of ISRFT, this study first develops a theoretical model of ISRFT-ground contact and proposes a modified non-linear ground pressure distribution. Subsequently, the verification and estimation of the parameters related to the modified non-linear ground pressure distribution were conducted. The lateral and longitudinal forces of ISRFT under various load and pressure conditions were then examined in conjunction with the brush tyre model. The results demonstrate that the modified non-linear ground pressure distribution exhibits a high degree of fitting accuracy, with a maximum error of 5.27% between theoretical and simulation. The lateral force increases rapidly when the slip angle is less than 3°, and slows down when it exceeds 3°. Furthermore, the slip angle at which the maximum lateral force occurs under zero-pressure conditions is 3–5° greater than that under standard pressure. The longitudinal force exhibits a rapid increase when the slip rate exceeds −0.2, and then plateaus as the slip rate further increases. It is noteworthy that the maximum longitudinal force under zero-pressure conditions is 23.33% lower than that under standard pressure. This research lays a theoretical foundation for the mathematical modelling of ground pressure distribution of ISRFT and provides a reference for analysing tyres and vehicles mechanical characteristics. • The theoretical models of ISRFT-ground under different pressure conditions are established. • The modified non-linear ground pressure distributions of ISRFT considering different radial loads are proposed. • The mechanical and dynamic characteristics for vehicles equipped with ISRFT and NT are compared. • Results indicate the modified non-linear ground pressure distributions of ISRFT have high accuracy. • Results indicate ISRFT preserves vehicle control under zero-pressure conditions, but with less force and steering. [ABSTRACT FROM AUTHOR]

Non-pneumatic tyre technology can overcome the safety problems of traditional pneumatic tyres. Hence, it is expected to improve driving safety significantly. Accordingly, in recent years, this technology has received extensive attention. This paper reviews the status of research of non-pneumatic tyres and discusses their development trends. Initially, the fundamental concept of non-pneumatic tyres is introduced, and their structural characteristics are described in detail. Subsequently, the research progress on the material properties of non-pneumatic tyre components is summarised. The research results on the mechanical properties of non-pneumatic tyres are recapitulated in terms of vertical mechanical, longitudinal mechanical, lateral mechanical, grounding, vibration, and fatigue characteristics. Moreover, the advantages and disadvantages of non-pneumatic tyres are analysed. Three prevailing forming technologies and tyre performance tests are discussed. The application of intelligent materials and structures to non-pneumatic tyres is proposed for these tyres to be lightweight, functional, and intelligent. Finally, the technical problems that must be resolved in the study of non-pneumatic tyres and the anticipated development trends are presented in this paper.

The long‐term characteristics and durability of alkali‐activated mortars based on waste glass are crucial to better understand their performance in aggressive environments. In this regard, the performance of waste glass as a building material and its characteristics such as mechanical (compressive, flexural, and tensile strengths), durability (chloride migration coefficient, sulfate resistance, and drying shrinkage), and microstructural properties [x‐ray diffraction (XRD), Fourier transform infrared (FTIR), and scanning electron microscopy (SEM) with energy dispersive x‐ray analysis (SEM/EDX)] were evaluated. For this purpose, the specimens with different amounts of silica modulus and Na2O content were prepared. The specimens were cured at 95°C for 20 h and then kept at a relative humidity of 50% at room temperature until testing. The specimen with 10% Na2O and a silica modulus of 1.5 demonstrated the highest compressive, flexural, and tensile strengths. The specimens illustrated a lower chloride migration coefficient and lower expansion than the Portland cement one. By increasing both silica modulus and Na2O contents, the drying shrinkage of the specimens increased due to the presence of more free water. The microstructural results indicated that amorphous gels such as sodium aluminum silicate hydrate (N‐A‐S‐H) and sodium (calcium) silicate aluminum hydrate [N‐(C)‐A‐S‐H] were formed. The results of this study signify the utilization possibility of waste glass as an eco‐friendly material with desirable characteristics. [ABSTRACT FROM AUTHOR]

This research has developed the slice test device to test natural rubber composites made of magnetically modified natural zeolite on nanosilica-reinforced natural rubber composites. We tested the sample similarity with incision cadavers in surgical practice with mechanical characteristics like human tissue. Natural rubber was used as a primary component in the production of synthetic human tissue. The natural rubber was blended with magnetic particle nanosilica, an alternative filler that mixes nanosilica, natural zeolite, and magnetite. This project used several materials formulas to give synthetic human tissue the desired mechanical qualities and incision test characteristics. We used technical specifications rubber (TSR) SIR 20 with nanosilica reinforced fillers and Titanate coupling agent (TCA) as filler and elastomer binders. Samples were characterized using Universal Testing Machine and then tested with the incision test equipment specially designed by the team. Mechanical characteristics of different human body part tissue were compared to the control samples and had similar mechanical characteristics with internal human tissue characteristics. It was found that nanosilica fillers combined with magnetically modified zeolites and titanate coupling agents are potentially applicable for synthetic muscle replacement cadavers with a custom formula.

This paper focuses on the development of high-flowability liquefied stabilized soils (HFLSS) made of recycled construction sludge (RCS) to enhance their application in construction work. Liquefied stabilized soils (LSSs) have already found widespread use in construction sites, particularly for filling long-distance structures and dealing with complex underground spaces. However, to further optimize their performance, the development of high-flowability liquefied stabilized soils (HFLSSs) with superior flowability is required. This study experimentally investigates the basic properties, including mechanical characteristics and flowability performance, of the newly developed HFLSS made of RCS. The results confirm that the developed HFLSS made of RCS meets the quality requirements expected from LSSs and exhibits enhanced flowability, making it a promising material for construction applications. The advanced development of LSSs in this paper expects to promote recycling construction-generated soils, including construction-generated sludges in the construction industry.

There have been no reports of the simultaneous application of natural fillers, such as magnetite and natural zeolites, to increase the strength of composites containing silica (SiO2) fillers as reinforcing fillers in natural rubber. This study has investigated the effect of magnetically modified natural zeolite on nanosilica-reinforced natural rubber composites that include a mechanical characteristic like human tissue. We use technical specifications rubber (TSR) SIR 20 with nanosilica reinforced fillers and Titanate coupling agent (TCA) as fillers and elastomer binders. The results showed that the nanosilica-zeolite-magnetite (Fe3O4) mixture had an influence on strength and stiffness and could be a substitute filler. The precursors made with some variations include the optimization of filler and the optimization volume fraction of nanosilica. Mechanical characteristics of different human body part tissue were compared to the control samples and have similar mechanical characteristics with internal human tissue characteristic. Based on these results, nanosilica fillers combine with magnetically modified zeolites and titanate coupling agents, potentially as an alternative filler to replace carbon black, and are applicable for synthetic muscle replacement cadavers with a customized formula.

Gabion mixed media is an important ecological protection method for preventing riverbank scouring. It is favored by engineers for its use of local materials, low carbon footprint, and environmental friendliness. However, the mechanical characteristics of gabion mixed media are closely related to the shape of the gabion mesh, the diameter of the gabion wire, and the type of internal media. Thus, its macroscopic properties are difficult to analyze. Therefore, this study adopts a discrete element method, Particle Flow Code 3D (PFC3D), to establish a numerical calculation model of gabion structures. This method analyzes the mechanical characteristics of gabion structures filled with spherical and oblate stones by considering porosity, mesh shape, filler size, and mesh size. Key results demonstrate that the bearing capacity and stability of a gabion structure filled with oblate stones is stronger than that of a gabion structure filled with spherical stones, with an increase of about 25 % in bearing capacity. Porosity and mesh shape have a considerable effect on the compressive strength of the gabion structure. Compared with high-porosity gabion structures, low-porosity gabion structures have a 50 %−65 % increase in compressive strength. Additionally, hexagonal mesh gabion structures exhibit better stability than quadrilateral mesh gabion structures and under axial loads, the hexagonal mesh is less prone to breakage. Increasing mesh size may cause smaller fillers to overflow, reducing the porosity of gabion structures and resulting in decreased compressive strength. The results of this study can provide a basis for estimating integrated parameters of gabion mixed media and determining slope stability. • Random reconstruction of stone fillers and correction of gabion wire parameters improve the experimental results' reliability. • Gabion structures filled with oblate stones exhibit stronger bearing capacity compared to those filled with spherical stones. • Gabion structures with low porosity and hexagonal mesh display greater compressive strength and better stability. • Larger mesh sizes can lead to filler overflow, reducing porosity and compressive strength. [ABSTRACT FROM AUTHOR]

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At present, the research considering multi-factor softening conditions is rarely performed, and the research on the deformation law and mechanical properties of the tunnel in diatomite is even rarer. Diatomite is easy to soften in water, and its physical and mechanical properties change greatly after softening. Therefore, take the high-speed railway tunnel that passes through the diatomite stratum in East China as an example, considering various softening conditions (including softening degree and softening position), the deformation law and mechanical characteristics of the tunnel are obtained, and corresponding suggestions are also put forward according to different softening conditions. The results show that the deformation law and mechanical characteristics of the tunnel are greatly affected by the symmetry of softening part. The deformation of the inverted arch caused by the lower surrounding rock softening of the tunnel is the largest, and the maximum stress occurs at the arch foot when the upper surrounding rock of the tunnel softens. Different softening degrees and positions have a great influence on the mechanical characteristics and deformation law of the tunnel. The results obtained in this paper may provide some important references for similar projects in the future. [ABSTRACT FROM AUTHOR]

Loading tests were carried out on the dowel bar-concrete substructure of concrete pavement. Mechanical characteristics of dowel bar-concrete interaction were studied. In the elastic range of concrete, the bearing modulus, which is a crucial parameter but is usually determined by presumption, was calculated using classic Westergaard equations. Its influencing factors were evaluated such as concrete strength, dowel bar thickness, joint width, and anti-cohesive layer. Besides, a theoretical equation for tangential stress at the most dangerous point of concrete was deduced from Westergaard's and Timoshenko's equations. The equation reveals how the tangential stress of the most dangerous point at the dowel bar-concrete interface is affected by influencing factors. Lastly, the deterioration process of concrete around the dowel bar was revealed. The strain gauges' data show that deterioration of concrete develops from the most dangerous point to far away from the dowel bar gradually. Two failure modes were found; one is circular spalling, the other is three main cracks. The initiation of the dowel-bar concrete structure's deterioration is circular spalling, attributed to high radial compressive stress in concrete. The deterioration starts around half the load capacity of the structure. [ABSTRACT FROM AUTHOR]

Copyright of Railway Investigation & Surveying is the property of Railway Investigation & Surveying Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)