Increase In Strength Research Articles

Performance of circular CFST columns strengthened with CFRP grid-reinforced ECC under axial compression: Numerical modelling and design

This paper describes a detailed numerical investigation using finite element models validated against test results from an experimental investigation on concrete-filled steel tubular (CFST) columns strengthened with carbon fiber-reinforced polymer (CFRP) textile grid-reinforced engineered cementitious composite (ECC). The three-dimensional model incorporates the confinement effects provided by the ECC, CFRP grid layers, and the circular tube. The validated model is used to evaluate the performance of strengthened CFST short columns through parametric assessments covering different geometric and material properties. Range analysis is applied in an orthogonal design to evaluate the relative significance of key parameters influencing the ultimate axial strength of the column member. The findings reveal a nearly 24 % increase in ultimate strength and over a 42 % enhancement in the residual strength of the concrete core due to the strengthening configuration. Additionally, the composite action of the CFRP grid-reinforced ECC leads to a 13 % increase in ultimate axial strength and over a 28 % improvement in the residual strength of the CFST column. The tube diameter is shown to have the greatest impact on the column axial resistance, followed by ECC thickness, ECC compressive strength, core concrete compressive strength, tube yield strength, tube thickness, and the number of CFRP grid layers. Finally, a simplified design model, which is supported by the experimental and numerical results, is introduced for the prediction of the compressive capacity of strengthened circular CFST columns.

Tailoring yield strength in Fe-20Mn-9Al-1.5C-3Cr-2Ni austenitic lightweight steels achieved by larger volume and size κ′-Carbide under extended aging

We investigate the microstructural evolution and its effects on mechanical properties of Fe-20Mn-9Al-1.5C-3Cr-2Ni austenitic lightweight steel, with particular emphasis on the intragranular κ’-carbides that are coherent with the austenitic matrix. By varying the aging treatment, we obtained different sizes and volume fractions of these coherent κ′-carbides. Our results reveal that the larger volumes and sizes κ′-carbides significantly contribute to the ultra-high yield strength (YS) of 1269 MPa while maintaining good total elongation (TEL) of 25.0 %. The YS arises from a combination of precipitation strengthening, solid solution strengthening, and grain boundary strengthening. Notably, precipitation strengthening was pivotal, contributing to an increase in strength of 501 MPa as the aging time was extended to 2040 min.

Anisotropy in shear failure of shale: An insight from microcracking to macrorupture

Anisotropic shear failure in shale is crucial to wellbore instability and hydraulic fracturing. While previous studies have examined bedding angles ranging from 0° to 90°, the intermediate angles have not been thoroughly investigated, with limited quantitative analysis from microcracking to macrorupture. To address this gap, we conducted direct shear tests on cubic shale samples with seven bedding angles (α = 0°, 15°, 30°, 45°, 60°, 75°, and 90°) using an innovative combination of acoustic emission (AE) and digital image correlation (DIC) techniques. This approach allowed us to gain a comprehensive understanding of the cracking damage process from the interior to the surface. Under various normal stresses, the minimum peak shear strengths occurred at α = 0°, while the maximum values were observed at α = 45° or 60°, rather than remaining constant. The internal friction angle peaked at α = 45°, not at α = 30° as previously reported. Furthermore, the shear failure pattern was influenced by complex interactions among nominal shear plane, bedding structure, and normal stress. The primary strain concentration zones and microfractures formed not only along the nominal shear plane but also along the bedding planes. Notably, microcracking damage initiated most readily at α = 0°, where the b value in AE events was higher and the fractal dimension was lower. At α = 30°–60°, the b value reached its minimum, while the fractal dimension peaked. The more random distribution of larger-scale microcracks was associated with an increase in the shear strength. These findings provide critical insights into the anisotropy of shear failure in shale and demonstrate the potential of microcracking analysis in predicting critical macrorupture and shear resistance. The identification of three distinct shear failure mechanisms further enhances our understanding of shale anisotropy.

Enhancing fruit preservation with sodium alginate films incorporating propolis extract and graphene oxide.

In this work, sodium alginate (SA) composite films containing propolis extract (PRO) and graphene oxide (GO) were developed. Subsequently, the effects of PRO and GO on different properties of SA composite films were studied, and the films were characterized by scanning electron microscopy, fourier transform infrared spectroscopy, X-ray diffraction, and thermogravimetric analysis. The PRO release properties and fruit preservation performance of the developed composite films were also investigated. The results showed that the incorporation of PRO resulted in a 51.16% increase in tensile strength. The simultaneous incorporation of PRO and GO reduced water vapor permeability (WVP) by 22.56% compared to the SA film. The temperatures at which the SA/GO/PRO film lost 5% of its weight were 8.0°C higher than those of the SA film. The incorporation of GO into the SA/PRO composite film also modulates the release of PRO. Furthermore, the incorporation of PRO and GO improved the tensile strength of the SA film, as reflected in the microstructure of the films. The reduced WVP of the SA composite film allowed the packaged blueberries to exhibit less weight loss and shrinkage, thereby prolonging their shelf life.

Impact of Virtual Reality Task-Oriented Training on Upper Extremity Motor Function in Children with Cerebral Palsy

This study aims to investigate the effect of a newly developed virtual reality task-oriented training (VR-TOT) video game on upper extremity fine motor function compared with conventional occupational therapy through leap motion in children with spastic hemiplegic cerebral palsy (CP). In this double-blind randomized clinical trial, 30 children with spastic hemiplegic CP aged six to 10years were included and randomly allocated into two groups. During six weeks, 15 patients in the intervention group received VR_TOT-based video game in addition to conventional occupational therapy, whereas 15 patients in the control group received only conventional occupational therapy. The outcomes of spoon and knife use time, as well as wrist extension range of motion (ROM), and handgrip strength were evaluated pre- and postintervention, and also at six-week follow-up. The reduction in spoon (6.27±3.08 vs 2.55±2.08; P<0.001) and knife (7.44±1.95 vs 2.74±2.46; P<0.001) usage time was significantly greater among children in the intervention group compared with the control group. The increase in grip strength was significantly higher among intervention group children (1.57±1.28 vs 0.50±0.77; P=0.011). However, the wrist extension ROM was not different between intervention and control groups. The results show that combining the VR-TOT with traditional occupational therapy methods improves fine motor function and grip strength in children with CP.

Influence mechanism of AC electric field on rime ice accretion on the insulator and its experimental verification in the natural environment

Insulator icing can easily trigger flashover trips in heavily ice-covered areas, and analyzing the formation mechanism of ice accumulation on the insulator is essential for predicting its flashover development. To accurately dissect the process of insulator icing, a coupled mathematical model of the flow field and electric field, as well as a droplet motion model were elaborated in this paper based on the principles of fluid mechanics and electromagnetic field. Subsequently, the characteristics of droplet motion deviation and its physical collision process with an insulator surface under AC electric field were investigated. The results demonstrate that the charged droplets tend to oscillate along the electric field lines in AC electric field, and the amplitude of the oscillation increases with the applied voltage increasing. Moreover, the number of droplets captured by the insulator rises with the increase of voltage, wind speed, and median volume diameter of the droplet. Combined with the simulation and natural icing experiments, it is observed that ice branches grow in the direction of electric field force, and as the voltage rises, ice branches gradually spread from the edge of the shed to its surface, increasing surface roughness. The density of ice exhibits an inverted U-shaped relationship as the electric field strength increases. Ice mass and ice length present nonlinear growth with an increase in icing time. Furthermore, compared with that without energization, the icing amount and icing length increase by more than 13 % under AC voltage of 40 kV.

Ryegrass root-soil composites mechanical properties and its slope stability: Experimental study and numerical analysis

ABSTRACT Urbanization and infrastructure projects generate huge amount of construction and demolition waste (CDW), posing significant challenges for the environment and human health. In order to reduce the environment and safety risks caused by the CDW landfills, this study was amid to utilize plant roots to develop a root-CDW-soil system for strengthening the CDW and enhancing the slope stability of CDW landfills. A series of experimental analyses were conducted, focusing on shear tests of root-soil composites under various moisture conditions and root content ratios. The results indicate that the inclusion of ryegrass roots plays a critical role in significantly enhancing the shear strength of the soil, and the soil samples reinforced with 0.6 g of ryegrass roots exhibited a shear strength increase of up to 35% compared to the unreinforced samples. The slope stability treated by the plant roots was evaluated by finite element simulations under different rainfall conditions. The factor of safety (FoS) for reinforced slopes increased from 1.18 to 1.59 after five days of heavy rainfall (480 mm/d), highlighting the significant improvement in stability provided by the root systems. These findings suggest that the root-soil system offers a sustainable solution for slope management, reducing risks associated with construction waste and extreme weather conditions. Implications: Urbanization and infrastructure projects generate significant waste, posing environmental and safety challenges. This study investigates the enhancement of slope stability through the integration of ryegrass root systems. The findings indicate that ryegrass roots substantially improve soil shear strength and overall slope stability. Furthermore, the study demonstrates that these root systems enhance resilience to heavy rainfall, thereby mitigating the risk of slope failure. These results suggest that plant root systems offer a sustainable solution for slope management, effectively addressing environmental concerns related to construction waste and extreme weather conditions. This research provides a comprehensive understanding of the physical and mechanical properties of root-soil composites, thereby promoting their practical application in slope stabilization.

Sulfate attack, freeze-thaw and high-temperature performances by evaluation of colemanite waste as binding material and aggregate in green geopolymer production

To turn the construction industry into a green application phase, alternatively, cementitious source materials have been partially or completely replaced by waste materials and industrial by-products. With this situation, boron minerals and products have a wide usage area and are increasing daily. The most common of the boron minerals is colemanite. In this study, in addition to using blast furnace slag (S) and fly ash (FA) as source materials in geopolymer mortar production, the mechanical and durability performances of geopolymer mortars by evaluating colemanite waste (CW) instead of both source material and aggregate were compared with 10 different series cured at room temperature. Mechanical properties were investigated on the 7th, 28th, and 90th days. For the durability study, a high-temperature test (300, 600, and 900 °C), freeze-thaw test (15 cycles), and sulfate solution attack test (10% magnesium sulfate (MgSO4) and sodium sulfate (Na2SO4)) were performed. Also, SEM, XRD, and TGA-DTA analyses were used to examine the situation before and after the durability tests. Substitution of colemanite waste up to 10% as a source material allowed it to show a strength increase. The highest compressive strength result on the 90th day was 39.06 MPa in the series where it was replaced with 5% fly ash. In the case of using colemanite as an aggregate, results close to the control sample were obtained. In the high temperature and freeze-thaw test, the colemanite waste formed a protective layer and provided better results in the series in which it was replaced by slag and used as an aggregate.

The impact of interplanetary magnetic field intensity on the Martian ionosphere

The interplanetary magnetic field (IMF) is one of the important external drivers that controls the Martian-induced magnetosphere and ionosphere. Previous studies have shown that the ion escape process is highly influenced by both the direction and intensity of the IMF. The enhanced IMF may decrease the ion escape rate by inducing a stronger magnetosphere that protects the Martian ionosphere, but the mechanisms have not been investigated thoroughly. Further studies are needed to reveal the response of ionospheric heavy ions to IMF variation as well as the underlying physical mechanism. This study aims to investigate the influence the IMF strength has on the Martian ionosphere. We adopted a multifluid magnetohydrodynamic (MHD) model in this study, which can self-consistently simulate the interaction between solar wind and Mars. By comparing different cases, we analyzed the ionospheric structure on the dayside and near nightside as well as the ion transport process. We aim to obtain a deeper understanding of how the IMF intensity variation impacts the Martian ionosphere and the escape of planetary ions. A three-dimensional multifluid MHD model was used to simulate the interaction between the upstream solar wind and Mars. Four major species in the Martian ionosphere, H^+, O_ O^+, and CO_ are considered in the model, with the chemical reactions and particle collisions included to calculate ion distribution and ion motions. We analyzed three cases where the IMF strength was set to nT ， nT and nT The enhancement of the IMF produces a stronger electromagnetic field in the Martian plasma environment. Both the electric field and magnetic field intensity increase, which provides a shielding effect to the Martian ionosphere, hindering the intrusion of solar wind particles. Thus, less planetary ions are produced by the chemical reactions between the solar wind and the Martian neutral particles, leading to shrinkage of the ionospheric upper boundary. As the IMF strength increases, both the day-to-night plasma transport and the ion outflow decreases. Thus, a more depleted nightside ionosphere is formed, and the tailward ion escape may be weakened, decreasing the global ion escape rate. Moreover, the strong crustal fields in the southern hemisphere enhance the electromagnetic field on the southern dayside, which withstand the penetration of solar wind plasma more effectively, resulting in asymmetry structures in the ionosphere.

Structural evolution of particle configurations: Zero-temperature phases under increasing confinement.

In this study, we investigate the phase behavior and structural organization of colloidal particles in a two-dimensional (2D) system under isotropic harmonic confinement using overdamped Langevin dynamics simulations. We employ a modified mermaid potential, which introduces an additional short-distance term resulting in a null-force region, distinct from the conventional mermaid potential. This modification facilitates a richer exploration of self-assembled structures, revealing a variety of phases influenced by the interplay between confinement strength V0 and the interaction potential. Our analysis spans a wide range of parameters, resulting in a detailed phase diagram that captures transitions from dispersed clusters to well-ordered patterns, including square, triangular, rhomboidal, and mixed configurations, as the confinement strength increases. The findings underscore the intricate balance of forces governing the self-assembly of colloidal systems and offer valuable insights for future experimental realizations.

Transforming contaminated biosolids into biochar for a sustainable cement replacement material

Abstract Contaminated biosolids especially with per- and polyfluoroalkyl substances (PFAS) in biosolids pose significant environmental risks, restricting their potential applications and necessitating sustainable solutions to address these challenges. In this context, pyrolysis emerges as a promising technology capable of degrading contaminants while transforming biosolids into useful products like biochar. This study demonstrates the application of pyrolysis at different temperatures of 450–750 °C to investigate its effect on contaminant removal and the properties of the resulting biochars. Subsequently, the biochars were utilized to prepare cement mortars by replacing 0.5, 1, 2, 4, and 6% of cement weight with biochar, and their compressive strengths were determined after 7 days of curing. The findings revealed that biosolids contained significant levels of PFAS, including perfluorooctanesulfonic acid (PFOS), 324 ng/g, perfluorohexanesulfonic acid (PFHxS), 9.15 ng/g, and heavy metals. Pyrolysis at 450 °C effectively degraded most contaminants, including PFAS. The biochar produced at 450 °C exhibited the highest concentrations of inorganic nutrients such as potassium (K), calcium (Ca), nitrogen (N), and phosphorus (P), though their levels decreased with increasing pyrolysis temperature. On the other hand, compressive strength tests for cement mortars with varying proportions of biochar replacement demonstrated that a 0.5% replacement was beneficial for all biochars (except 650 °C—biochar that achieved the maximum compressive strength with 2%). This resulted in a 30–45% increase in compressive strength compared to plain cement mortar. However, increasing the biochar content to 6% significantly reduced compressive strength. Overall, this study highlights the potential of biochar as a sustainable solution for enhancing cement mortar strength while mitigating biosolid contamination. Graphical abstract

Evaluation of mechanical and wear properties of LM24/fly ash/titanium diboride hybrid metal matrix composites using stir casting

This study focuses on the development of novel hybrid composites based on the LM24 alloy, utilizing liquid metallurgy stir casting to incorporate dual reinforcements (titanium diboride (TiB2) and fly ash (FA)). The weight percentage of TiB2 was maintained at levels of 2.5%, 5%, and 7.5%, keeping the FA at 2.5% during the course of fabrication. The introduction of 7.5 wt% TiB2 and 2.5 wt% FA displayed a very notable 43.18% increase in hardness and a 21.53% increase in tensile strength of the hybrid composite compared to the LM24 alloy. Furthermore, hybrid composites with a total reinforcement of 10 wt% exhibited superior wear resistance across the entire range of applied loads. Tensile fractography revealed ductile fracture mode for the LM24 alloy, while hybrid composites displayed a mixed-mode fracture. High-load-induced abrasive wear with little plastic deformation was seen on worn surfaces of hybrid composites, whereas adhesive wear was the dominant type of wear in the LM24 alloy. The results show that hybrid composites have better mechanical and tribological properties because the reinforcement particles are well distributed and the load is transmitted optimally. However, it is noted that increased reinforcement levels lead to a reduction in ductility, resulting in decreased impact resistance for the hybrid composites.

Optimized Heat Treatment for Electron Beam Powder Bed Fusion Processed IN718: Correlating Microstructure, Texture, and Mechanical Properties

This study investigates the microstructure and mechanical properties of Inconel 718 (IN718) manufactured via electron beam melting (EBM). The EBM‐processed IN718 exhibits a unique grain structure with columnar grains along the build direction (BD) and equiaxed grains perpendicular to it. Contrary to typical solidification textures, the strongest texture intensities are observed for (110) and (111) orientations, attributed to in situ δ phase precipitation during high‐temperature processing. The microstructure notably lacks cellular structures common in additively manufactured materials, instead featuring δ phase formed through in‐situ aging. A tailored heat treatment strategy is developed to control δ phase precipitation at grain boundaries, mitigating grain boundary sliding (GBS). This treatment results in &lt;100&gt; texture and large columnar grains, leading to a twofold increase in yield strength compared to the as‐printed (AP) condition. Interestingly, the AP EBM IN718 shows no signs of dynamic strain aging (DSA), distinguishing it from conventionally processed IN718. This comprehensive analysis of microstructure, texture, and mechanical behavior provides valuable insights for optimizing EBM processing and heat treatment of IN718 for enhanced performance in high‐temperature applications.

Heat-Responsive PLA/PU/MXene Shape Memory Polymer Blend Nanocomposite: Mechanical, Thermal, and Shape Memory Properties

This study investigates the fabrication and characterization of heat-responsive PLA/PU/MXene shape memory polymer blend nanocomposites with varying PLA content (10, 20, 30, and 50%) and a fixed MXene content of 0.5 wt.%. The results indicate significant improvements in mechanical properties, with the 50% PLA/PU/MXene blend showing a 300% increase in ultimate tensile strength and a 90% decrease in % elongation compared to pure PU. Additionally, the 50% blend exhibited a 400% increase in flexural strength. Microstructural analysis revealed dispersed pores and sea–island morphology in pure PU and the 50% PLA/PU/MXene blend. Thermal analysis using DSC showed an increase in crystallinity from 33% (pure PU) to 45% for the 50% PLA/PU/MXene blend, indicating enhanced crystalline domains due to the semi-crystalline nature of PLA and MXene’s influence on molecular ordering. TGA demonstrated a significant improvement in thermal stability, with the onset temperature rising from 185 °C (pure PU) to 212 °C and the degradation temperature increasing from 370 °C to 425 °C for the 50% blend, attributed to the rigid structure of PLA and MXene’s stabilizing effect. Shape memory testing revealed that the 30% PLA/PU/MXene blend achieved the best shape fixity and recovery with optimal performance, whereas higher PLA content diminished shape memory behavior.

Dragon Intermittency at the Transition to Synchronization in Coupled Rulkov Neurons

We investigate the synchronization dynamics of two non-identical, mutually coupled Rulkov neurons, emphasizing the effects of coupling strength and parameter mismatch on the system’s behavior. At low coupling strengths, the system exhibits multistability, characterized by the coexistence of three distinct 3-cycles. As the coupling strength is increased, the system becomes monostable with a single 3-cycle remaining as the sole attractor. A further increase in the coupling strength leads to chaos, which we identify as arising through a novel type of intermittency. This intermittency is characterized by alternating dynamics between two low-dimensional invariant subspaces: one corresponding to synchronization and the other to asynchronous behavior. We show that the system’s phase-space trajectory spends variable durations near one subspace before being repelled into the other, revealing non-trivial statistical properties near the onset of intermittency. Specifically, we find two key power-law scalings: (i) the mean duration of the synchronization interval scales with the coupling parameter, exhibiting a critical exponent of −0.5 near the onset of intermittency, and (ii) the probability distribution of synchronization interval durations follows a power law with an exponent of −1.7 for short synchronization intervals. Intriguingly, for each fixed coupling strength and parameter mismatch, there exists a most probable super-long synchronization interval, which decreases as either parameter is increased. We term this phenomenon “dragon intermittency” due to the distinctive dragon-like shape of the probability distribution of synchronization interval durations.

Effect of Plyometric Exercises of Lower Limb on Strength, Postural Control, and Risk of Falling in Stroke Patients

Background and Objective: Stroke, a major contributor to long-term disability worldwide, often results in significant impairments in motor function. These impairments can include weakness, impaired balance, and decreased coordination, which can have a significant influence on one’s quality of life and independence. Finding an effective protocol for rehabilitation to improve these points will decrease the impact of stroke and its coast of rehabilitation. Materials and Methods: This study was conducted to assess the effect of lower limb plyometric exercises on strength, postural control, and risk of falling in stroke patients. Materials and Methods: This study involved 40 chronic left stroke patients randomly divided into two equal groups. The experimental group participated in a 12-week supervised plyometric training program, while the control group received conventional physical therapy program. Lower limb muscle strength was measured using a handheld dynamometer, and balance and fall risk were assessed via the Biodex Balance System (BBS). These measurements were conducted before and after the intervention period to evaluate treatment effects. Results: The results of this study demonstrated significant improvements in muscle strength and balance parameters among stroke patients who underwent plyometric exercise compared to those receiving a conventional program. The plyometric group exhibited significantly greater increases in knee extension strength (p &lt; 0.05), hip abduction strength (p &lt; 0.05), ankle dorsiflexion strength (p &lt; 0.05), and ankle eversion strength (p &lt; 0.05). Furthermore, the plyometric group showed significant improvements in overall stability (p &lt; 0.05), mediolateral stability (p &lt; 0.05), and anteroposterior stability (p &lt; 0.05), as measured by the Biodex Balance System (BBS). Conclusions: The results of this study suggest that plyometric exercise may be an effective intervention for decreased risk of falling and enhancing muscle strength and balance during recovery from stroke.

Optimization of the Properties of Eco-Concrete Dispersedly Reinforced with Hemp and Flax Natural Fibers

Dispersed reinforcement of concrete with various types of plant fibers is currently a fairly popular area in the field of construction materials science. The relevance of this topic is determined by the fact that the issue has not been studied on a large scale in comparison with concrete reinforced with artificial fibers, and the fact that these types of concrete meet the requirements of the Sustainable Development Goals. The purpose of this work was to evaluate the efficiency of using hemp fiber (HF) and flax fiber (FF) for the dispersed reinforcement of concrete, and to compare their efficiency and practical applicability in the construction industry. Before use, HF and FF were treated with a NaOH solution and stearic acid to increase their resistance to the aggressive alkaline environment of concrete. A total of 15 concrete compositions were made. The percentage of dispersed reinforcement for both types of fibers varied from 0.2% to 1.4%, with a step of 0.2%. The standard methods of mechanical testing and microscopy for investigation the properties of fresh and hardened concrete were applied. The optimum amount of HF in concrete was 0.6%, which provided an increase in compressive and flexural strength of 7.46% and 28.68%, respectively, and a decrease in water absorption of 13.58%. The optimum percentage of FF concrete reinforcement was 0.8%, which allowed an increase in compressive and flexural strength of 4.90% and 15.99%, respectively, and a decrease in water absorption of 10.23%. The results obtained during the experiment prove the possibility and effectiveness of the practical application of hemp and flax fibers in concrete composite technology.

Two‐dimensional layered MoS2/lignin as additives for epoxy composites with improved mechanical and tribological properties

AbstractThe MoS2/lignin hybrid material was successfully synthesized and incorporated into an epoxy resin to fabricate composite coatings. The results demonstrate that MoS2 is uniformly attached to the surface of lignin sheets. Compared to adding lignin alone, the MoS2/lignin hybrid‐epoxy resin (EP) composite coatings exhibited enhanced friction‐reducing and wear‐resistant properties. Specifically, the 1 wt% MoS2/lignin hybrid displayed excellent dispersion and high interfacial compatibility within the resin matrix, leading to a 66.7% increase in Vickers hardness, a 27.5% increase in tensile strength, and a 73.9% improvement in char yield. Furthermore, the friction coefficient and wear rate were reduced by 63.2% and 75.8%, respectively. As a uniformly dispersed hybrid structure, the MoS2/lignin material can endure higher loads, autonomously repair defects, and form a stable and complete transfer film on the worn surface, demonstrating synergistic friction‐reducing and wear‐resistant effects within the epoxy resin matrix. Integrating MoS2 into a two‐dimensional material can provide a practical reference for designing polymer‐based hybrid materials with outstanding comprehensive properties.Highlights The MoS2/lignin hybrid material was successfully synthesized. MoS2 is uniformly attached to the surface of lignin sheets. The hybrid significantly enhances friction‐reducing and wear‐resistant properties. Vickers hardness increased by 66.7%, and tensile strength increased by 27.5%. The friction coefficient was reduced by 63.2%, and the wear rate was reduced by 75.8%.

The effect of steel fibres on the uniaxial compressive strength and tensile strength of soil-cement

ABSTRACT Soil-cement is gaining acceptance in the construction industry for use in the improvement of sandy soil, despite its low strength Research has attempted to increase the strength of this material by increasing the percentage of additives. The current study investigated the effect of steel fibre (SF) as a reinforcer on the performance, UCS and TS at different fibre contents, lengths, diameters and shapes. The results showed that the use of 2% straight fibre significantly increased the UCS and that the samples performed better than those containing hooked or crimped. A decrease in the SF length from 10 to 5 mm and increase in the diameter from 0.3 to 0.6 mm caused decreases in the UCS. The greatest increase in TS occurred with the addition of 2% hooked fibres and was 4.6 times the increase in strength without fibres. The reason for the increase in the strength of the samples was bridge-like performance of the SFs in the soil-cement. The use of SFs together with cement to improve sandy soil is a new and effective way of improving the mechanical behaviour of the soil. This indicates that the addition of SFs can be a step towards more optimal use of soil-cement in engineering projects.

Effects of exercise intensity on nutritional status, body composition, and energy balance in patients with COPD: a randomized controlled trial

BackgroundHigh-intensity exercise is recommended for the pulmonary rehabilitation of patients with chronic obstructive pulmonary disease (COPD); however, it can cause an energy imbalance due to increased energy expenditure. Here, we aimed to explore the effect of reducing exercise intensity on energy balance in patients with COPD experiencing high-intensity training-induced weight loss.MethodsAll participants underwent high-intensity endurance and resistance training for a 2-week preliminary period. Those who lost more than 1% of their weight were then randomized to either continue high-intensity exercise (AA group) or switch to low-intensity exercise (AB group) for another 2 weeks (experimental period).ResultsThe analysis included 30 participants (AA, n = 15; AB, n = 15). The AA group showed significant increases in body composition, dietary intake, nutritional status, muscle strength, and exercise capacity at week 4 than at week 2, with no significant changes in the AB group. After the experimental period, a greater proportion of the AA group had energy intake exceeding expenditure than did the AB group (80% vs. 40%).ConclusionsIn patients with COPD who lost body weight during pulmonary rehabilitation with high-intensity exercise, continuing this exercise had a more positive effect on body composition, nutritional status, physical function, and energy balance than did reducing exercise intensity. These results suggest the importance of continuing high-intensity exercise, while taking into consideration energy intake and nutritional therapy, even when body weight loss occurs during pulmonary rehabilitation in patients with COPD.Trial registrationThis study was retrospectively registered on the UMIN-CTR as UMIN000050976 on May 5, 2023.