High Load Conditions Research Articles

ТРИБОТЕХНИЧЕСКИЕ ИССЛЕДОВАНИЯ ВТОРИЧНЫХ БРОНЗОВЫХ ПОКРЫТИЙ

One of the features of agricultural machines is the use of a sufficiently large number of parts made of non-ferrous metals and alloys in their designs, since they have high antifriction properties, corrosion resistance, withstand significant specific loads and high speed conditions. Most often these are bronze plain bearings of the bushing type. Tribotechnical studies of coated samples based on secondary composite materials on a friction machine is an important direction in the development of technologies for the restoration and hardening of bronze parts and assemblies. Secondary composite materials are obtained from production waste by the electroerosion dispersion, which allows to reduce production costs and reduce the environmental burden. Such powders can be used to create repair coatings with high wear resistance. (Research purpose) The research purpose is performing a comparative analysis of the tribotechnical properties of coatings obtained usng secondary composite materials and electric spark processing. (Materials and methods) Samples with bronze coatings were produced for research. Conducted tests on the friction machine II5018. (Results and discussion) It was determined that coated samples based on secondary composite materials have higher wear resistance and less friction compared to uncoated samples. It was found that with increasing load and sliding speed, the difference in wear resistance and friction between coated and uncoated samples increases. The coating based on secondary composite materials is especially effective in conditions of high loads and sliding speeds. (Conclusions) Comparative tribotechnical studies of coated samples based on secondary composite materials have shown that such coatings can be an effective way to increase wear resistance and reduce friction in various machine components.

Heat transfer and rock-soil temperature distribution characteristics in whole life cycle for different structure sizes of medium-deep U-shaped butted well

Medium-deep U-shaped butted well (MUBW) is one of the most potential geothermal-heating way. However, the thermal interference may happen during long-term geothermal extraction period, which results in a heating performance attenuation. In this work, the heat transfer performance and surrounding rock-soil temperature distribution characteristics of MUBW in whole life cycle were investigated. The three-dimension full-size heat transfer model for long-term thermal extraction was proposed and the different structure sizes were considered. The results showed that the thermal interference is more likely to happen in a high heating load condition for the conventional structure size. By increasing horizontal length from 200 m to 600 m, the average specific heating load could increase by 26.1 %. When vertical depth increases to 3000 m, the heating load increases by 47.0 % at least. It is noted that the annual average inlet and outlet temperatures decrease by 5.1 °C in the whole life cycle, which should be considered in design on system operation. Additionally, the horizontal length of 600 m is large enough to avoid thermal interference in whole life cycle for MUBW with depth of 2000∼3000 m. This study has a practical meaning for ensuring a sustainable thermal extraction of MUBW.

Effect of Stellite12 and NiCrBSi HVOF coatings on the tribological behavior of CrN PVD film

CrN film deposited on the stainless steel substrate is easy to crack and peel off due to the intrinsic brittleness and the low load carrying capability, which severely constricts its practical utilization under high load conditions. In this paper, CrN/Stellite12 and CrN/NiCrBSi duplex coatings were produced by PVD and HVOF technologies, then the microstructure, mechanical, and tribological properties was studied, and compared with single CrN film. The HVOF layers improved the hardness, binding strength and load carrying capability of duplex coatings, the wear resistance also be enhanced significantly, especially for CrN/NiCrBSi. We analyzed the wear mechanism and discussed the influence of different HVOF coatings on the tribological behavior.

Visuospatial perspective-taking of a protagonist during narrative comprehension: the effects of task load and individual differences in visuospatial working memory.

This study examined whether visuospatial perspective uses the character perspective during narrative comprehension. Participants read narrative stimuli depicting the spatial positional relationships between characters and objects and judged whether the objects were on the left or right from the character's perspective. We manipulated whether the spatial positional relationships between characters depicted in the narrative stimuli resulted in a visuospatial perspective. We hypothesized that the high-load perspective-taking condition would indicate longer reaction times compared to the low-load perspective-taking condition, as shifting perspectives between characters in the high-load condition require more time for visuospatial perspective-taking. As predicted, the reaction time was longer for high-load perspective-taking than for low-load perspective-taking. During narrative comprehension, the reaction time for visuospatial perspective-taking must move virtually within the representation from the main character's perspective to that of another character. Visuospatial perspective-taking is involved in narrative comprehension.

Noise Analysis and Structural Optimization of Automobile Scroll Compressor Air Valve

The air conditioning compressor is a critical component in automobile heating, ventilation and air conditioning systems. However, compressor noise has long been a problem for automobile manufacturers. In recent years, the development and application of automobile air conditioning scroll compressors has increased significantly due to their low mechanical vibration and noise. However, their limitations in terms of airflow pulse and noise cannot be ignored, especially in low speed and high load conditions where the noise generated has a negative impact on driving and passenger experience. Noise and airflow pulses are important considerations that cannot be ignored. This study innovatively modifies the end cap structure of the scroll compressor, using the principles of expansion muffler and insertion tube structure, with the aim of improving the acoustic quality of the scroll compressor. The results show that the novel valve construction can significantly reduce the sound pressure level of the scroll compressor noise to a maximum of 75.20 dBA. The results of this study provide a theoretical basis and practical technical applications for future research and development in the automobile industry.

Experimental and numerical analysis of NdFeB magnets under static and dynamic loading conditions

Neodymium iron boron (NdFeB) magnets, known for their superior magnetic properties, are pivotal in various high-performance applications, ranging from electric motors to wind turbines. The durability and reliability of these devices significantly depend on the mechanical integrity of NdFeB magnets under various stress conditions. In this work, the mechanical behavior and failure processes of NdFeB magnets are experimentally studied by in-door tests. We specifically examine the failure behavior of these magnets when subjected to dynamic loads, employing the Split Hopkinson Pressure Bar test both with and without initial loading perpendicular to the pressure bar direction. Furthermore, to complement the experimental findings, the experiments are numerically reproduced with a hybrid finite-discrete element method titled Continuous-Discontinuous Element Method (CDEM). Within the CDEM framework the Johnson-Holmquist 2 constitutive model is considered for the material under high strain rate loading conditions. Most material parameters are determined by experimental data and theoretical analysis. This research not only enhances our understanding of the properties of NdFeB magnets but also provides valuable insights for engineers and researchers aiming to improve the material’s resilience and durability.

DRY SLIDING WEAR BEHAVIOUR OF CARBON NANOTUBE/ALUMINA/EPOXY HYBRID NANOCOMPOSITES

In the field of materials science, polymer composites have been extensively used in various industries such as marine, automotive, aerospace, sports and other industries due to their good dimensional stability and excellent structural properties. In this present research investigation, epoxy served as the polymer material, while multi-walled carbon nanotubes (MWCNTs) and alumina nanofillers were employed for reinforcing the matrix through hybridization. The wear characteristics of the composite material were examined under dry sliding conditions, employing a pin-on-disc machine with a track diameter of 50 mm. The load on the specimen was varied between low (20 N), medium (40 N) and high (60 N), while the weight fraction of the hybrid nanofillers underwent variations in a range of 0.1–0.5 w/% with an increment of 0.1 w/%. The results showed that the reinforcement of hybrid nanofillers significantly reduces the wear phenomena of the composite material. Hybrid nanocomposites with (0.1, 0.2 and 0.3) w/% of MWCNTs-Al2O3 exhibit noteworthy advancements in the wear resistance. Particularly the 0.3 w/% MWCNTs-Al2O3 hybrid nanocomposite demonstrates exceptional wear resistance compared to pure epoxy. The incorporation of 0.3 w/% of MWCNTs-Al2O3 results in a significantly improved wear resistance, with enhancements of (83, 81 and 80) % observed during low (20 N), moderate (40 N) and high (60 N) loading conditions, respectively, compared to pure epoxy. Similarly, deformation, delamination and filler plugging were observed with medium and high load. The surface morphology of the worn specimens was assessed through the application of field emission scanning electron microscopy.

The Influence of Injector Nozzle Diameter on High-Density and Lean Mixture Combustion in Heavy-Duty Diesel Engines

In order to improve the fuel economy of heavy-duty diesel engines under high-load conditions, based on the combustion pathway model, it is proposed that the proportion of lean mixture with 0 < Φ < 1 is the most important spray characteristic affecting the overall diesel combustion process. Answering the question of how to increase the proportion of lean mixture inside the spray is the key to achieving the efficient and clean combustion of diesel engines. This paper investigated the mechanism of injector nozzle diameter on the in-cylinder air–fuel mixture and combustion process based on a high-density and lean mixture characteristic combustion strategy. The experimental results show that with an increase in nozzle diameter, the peak pressure and instantaneous heat release rate significantly increase, the combustion duration is shortened by about 20%, and the heat release becomes more concentrated. At 1200 rpm and IMEPg~2.3 MPa conditions, the indicated thermal efficiency increases by 1.3%, reaching a maximum of 51.5%. The numerical simulation results show that with the increase in nozzle diameter from 0.169 mm to 0.218 mm, the spray ejection momentum per unit time increases by 30%, the momentum transferred to the air by the spray increases, the oxygen transport process becomes more intense, and the air entrainment mass during the spray free development stage increases by 42%. The proportion of lean mixture inside the spray throughout the entire spray development process increases, resulting in an increase in the heat release rate of the lean mixture, making the overall combustion more intense and concentrated.

Youth-like brain activation linked with greater cognitive training gains in older adults: Insights from the ACTOP study

This study investigates the relationship between inter-individual neurofunctional differences in older adults and cognitive training efficacy, with a specific focus on the association between youth-like task-related brain activation and improvements in working memory (WM) training. The data is part of the Attentional Control Training for Older People (ACTOP) study, 30 older adults completed 12 half-hour WM training sessions. The WM performance slope, assessed at the conclusion of sessions 1 through 6 and sessions 7 to 12, determined early- and late-stage training gains, respectively. Transfer measures were taken before (PRE), midway (MID), and after (POST) training, and the differences in MID-PRE and POST-MID on transfer tasks were used to determine early- and late-stage transfer effects, respectively. The Goodness of Fit (GOF) metric was used to quantify the similarity between each older adult's activation pattern, as measured with functional magnetic resonance imaging (fMRI), to that of a group of younger adults. GOF scores were calculated for activation during low-load (1-0back) and high-load (2-0back) N-back tasks. The results indicated that larger GOF scores in the low-load condition were associated with greater training gains in both the early and late learning stages, and that larger GOF scores in the high-load condition were associated with greater training gains during the late-stage. These findings suggest that a youth-like brain activation pattern in older adults is associated with greater cognitive training benefits, underscoring the role of inter-individual neurofunctional differences to account for variations in training outcomes among older adults. Trial registrationClinicalTrials.gov NCT03532113; https://clinicaltrials.gov/ct2/show/NCT03532113.

Cross-linking Cu-TCPP@CNT-OH-S as high sulfur loading cathode for Li-S batteries

To obtain high theoretical energy density, lithium–sulfur batteries (LiSBs) with high sulfur loading are urgently required. Herein, sulfur was effectively immobilized on hydroxylated carbon nanotubes (CNT-OH) through chemical reaction deposition strategy to obtain CNT-OH-S, then combining with 2D Cu-TCPP nanosheets (TCPP = tetrakis (4-carboxyphenyl) porphyrin) successfully fabricated a 3D cross-linking Cu-TCPP@CNT-OH-S network, where CNT-OH-S carries the effective polar bond confirmed by FTIR, XPS and SAED tests, and Cu-TCPP promises the inhibition of LiPSs shuttle and promotes kinetics for sulfur conversion explored by UV–vis, symmetrical electrodes tests and XRD in suit. The fast diffusion of Li+ was calculated through CV, and the low electrochemical polarization was demonstrated by GITT, Tafel, GCD, etc., ensuring a high S utilization under practical conditions of high loading. As a consequence, the Cu-TCPP@CNT-OH-S@S cathode with 92.8 wt% sulfur content delivers a high specific capacity of 1448 mAh g−1 at 0.2C, and stabilize at 820 mAh g−1 after 900 cycles. In Li–S pouch cell, a 4.3 mAh cm−2 reversible areal capacity with 10.04 mg cm−2 sulfur loading was obtained at 2C after 100 cycles, which is in the top class among reported porphyrin-based, MOFs-based and nanocarbons-based cathode host.

Nanodiamond Coating in Energy and Engineering Fields: Synthesis Methods, Characteristics, and Applications.

Nanodiamonds are metastable allotropes of carbon. Based on their high hardness, chemical inertness, high thermal conductivity, and wide bandgap, nanodiamonds are widely used in energy and engineering applications in the form of coatings, such as mechanical processing, nuclear engineering, semiconductors, etc., particularly focusing on the reinforcement in mechanical performance, corrosion resistance, heat transfer, and electrical behavior. In mechanical performance, nanodiamond coatings can elevate hardness and wear resistance, improve the efficiency of mechanical components, and concomitantly reduce friction, diminish maintenance costs, particularly under high-load conditions. Concerning chemical inertness and corrosion resistance, nanodiamond coatings are gradually becoming the preferred manufacturing material or surface modification material for equipment in harsh environments. As for heat transfer, the extremely high coefficient of thermal conductivity of nanodiamond coatings makes them one of the main surface modification materials for heat exchange equipment. The increase of nucleation sites results in excellent performance of nanodiamond coatings during the boiling heat transfer stage. Additionally, concerning electrical properties, nanodiamond coatings elevate the efficiency of solar cells and fuel cells, and great performance in electrochemical and electrocatalytic is found. This article will briefly describe the application and mechanism analysis of nanodiamonds in the above-mentionedfields.

Insight into the tribological properties of cylinder liner-piston ring under the nano BNNs/Cu composite additive lubrication

To improve the tribological properties of the cylinder liner-piston ring, a two-dimensional hexagonal boron nitride/copper composite lubricant additive was prepared and characterized in detail. The tribological properties and lubrication mechanism of nano hexagonal boron nitride composites with different concentrations were studied through the reciprocating friction test on the Rtec friction and wear tester. The results show that copper is successfully reduced and attached to the surface of h-BN nanosheets through the self-polymerization of dopamine, and the spherical structure promotes the interlayer slip of the nanosheets during the reciprocating friction process. The appropriate concentration of nano composite additives has excellent anti-friction and anti-wear properties. At 1 Hz and 100 N, the friction coefficient and wear quality of the nano composite additive with a concentration of 2 wt% were reduced by 29.07% and 76%, respectively. The surface Sq value and Sz value of the cylinder liner sample decreased by 68.06% and 74.47%. At the same time, under the condition of high speed and heavy load, the average wear depth of the cylinder liner sample is reduced by 61.3%. The nano composite material additive forms an excellent friction protective film on the wear surface of the cylinder liner, which can better enter the wear surface of the cylinder liner and produce a filling and repairing effect. The research results provide a method for the use of nano hexagonal boron nitride composite additives to inhibit the wear of cylinder liner-piston ring of Marine diesel engines.

Unpacking the complexities of information overload in early-stage online booking: The moderating effects of information presentation and regulatory focus

Online Travel Agents (OTAs) have become pivotal marketing channels in the tourism and hospitality industry, providing tourists with a variety of rich and timely information. However, excessive information can lead to information overload, which can negatively affect the decision-making process and potentially lead to delayed or abandoned bookings. This study aims to investigate the role of information overload in tourists’ early decision-making in the context of online hotel booking. 2 (information load: high vs. low) × 2 (information presentation format: alternative-vs. attribute-based display) × 2 (regulatory focus: promotion-vs. prevention-focus) between-subjects scenario-based experiment was conducted with 305 Chinese adult participants. The results showed that information overload occurs in the early stages of online booking decision and is influenced by the interaction of information presentation format and regulatory focus. Regulatory focus can influence tourists’ information presentation format preferences under high information load conditions. When the appropriate information presentation format is applied to an individual's regulatory focus, information processing becomes more fluid, thereby reducing information overload. The findings emphasize the importance of matching information presentation to an individual's regulatory focus to minimize information overload and provide practical implications for OTAs.

Enhanced degradation of enrofloxacin in mariculture wastewater based on marine bacteria and microbial carrier

This study aimed to isolate marine bacteria to investigate their stress response, inhibition mechanisms, and degradation processes under high-load conditions of salinity and enrofloxacin (ENR). The results demonstrated that marine bacteria exhibited efficient pollutant removal efficiency even under high ENR stress (up to 10 mg/L), with chemical oxygen demand (COD), total phosphorus (TP), total nitrogen (TN) and ENR removal efficiencies reaching approximately 88%, 83%, 61%, and 73%, respectively. The predominant families of marine bacteria were Bacillaceae (50.46%), Alcanivoracaceae (32.30%), and Rhodobacteraceae (13.36%). They responded to ENR removal by altering cell membrane properties, stimulating the activity of xenobiotic-metabolizing enzymes and antioxidant systems, and mitigating ENR stress through the secretion of extracellular polymeric substance (EPS). The marine bacteria exhibited robust adaptability to environmental factors and effective detoxification of ENR, simultaneously removing carbon, nitrogen, phosphorus, and antibiotics from the wastewater. The attapulgite carrier enhanced the bacteria's resistance to the environment. When treating actual mariculture wastewater, the removal efficiencies of COD and TN exceeded 80%, TP removal efficiency exceeded 90%, and ENR removal efficiency approached 100%, significantly higher than reported values in similar salinity reactors. Combining the constructed physical and mathematical models of tolerant bacterial, this study will promote the practical implementation of marine bacterial-based biotechnologies in high-loading saline wastewater treatment.

Research on temperature rise characteristics of grease lubricated ball screw pair

Aerospace ball screws cannot be lubricated for maintenance and replacement, so they use grease that can run for a long time and keep the performance. Under high speed and high load conditions, the ball screw will be warmed up rapidly, and the temperature has a great effect on the capability of the grease. In this paper, we deduce the formula for calculating the screw temperature, establish a thermodynamic simulation of the ball screw model to get its temperature under different conditions, and set up a test bench to try out the screw temperature rise to investigate thermal properties in the grease lubrication conditions.

Two-phase cooling system for electric vehicles’ battery

The objective of this research project is to design an innovative cooling system for effectively managing the thermal conditions of batteries in electric vehicles. Electric vehicles commonly utilize Lithium-Ion cells as their power source. Despite significant advancements in Lithium-Ion technology from an electrochemical standpoint, the thermal management of these batteries remains a formidable challenge. This is primarily due to the demanding operational conditions that Lithium-Ion cells face during battery discharge, motion, and charging. The power supply unit in electric vehicles often demands high power outputs within short durations, leading to the generation of substantial heat by the batteries. This elevated working temperature poses a risk of decreased battery performance or even malfunction. Therefore, an efficient battery thermal management system is essential to optimize the performance of the batteries. In our research project, we propose and investigate a cooling system that is directly integrated into the power supply unit. Our study introduces an innovative thermal management system that combines two-phase direct liquid cooling with pulsating heat pipes. This system provides a compelling solution by combining high thermal efficiency, passive operation, and cost-effectiveness. Within this configuration, batteries are immersed in a low-boiling dielectric fluid contained in a Plexiglas container, facilitating efficient heat exchange. Simultaneously, the pulsating heat pipe operates to manage heat spikes by promoting vapor recondensation, thereby maintaining safe operational temperatures. The proposed battery thermal management system has demonstrated remarkable efficiency, ensuring that battery temperatures remain within the recommended range even under high load conditions. A notable advantage of this cooling system is its complete passivity, eliminating the need for energy-consuming coolant circulation.

Effect of loading conditions on short fatigue crack propagation behaviours in cast Al[sbnd]Si alloys

The effect of loading conditions on short crack propagation behaviours in cast AlSi alloys was investigated by a combination of photo-microscopy monitoring and post mortem analysis. The findings suggest that the path of short cracks is minimally influenced by loading conditions, whereas loading conditions significantly affect the fatigue crack growth rate (FCGR) and its statistical characteristics. Crack closure effect is observed under zero and negative stress ratio conditions. Roughness-induced crack closure occurs due to the coarse grain microstructure of cast AlSi alloys and the Stage-I mode growth of cracks within grains in the microstructural short crack regime. The high level of plasticity around the crack tip under negative stress ratio conditions has a significant impact on FCGR, resulting in a negative crack opening stress. When the stress ratio exceeds approximately 0.3, short cracks exhibit no crack closure. The load-level effect is observed only at high load conditions with negative stress ratios. Finally, a probabilistic short crack growth model was established using a Bayesian linear regression model to analyse the effect of stress ratio on the uncertainty of FCGR. After considering the crack closure effect, the difference in distributions of FCGR model parameters decreases significantly among different stress ratio conditions.

Influence of Few-Layer Graphene on Frictional Properties of Lithium Compound Grease

The frictional properties of lithium compound grease (LCG) with different percentage compositions of few-layer graphene (FLG) were investigated, and the mechanisms of temperature and loading effects on LCG containing FLG are also considered. The concluding effect shows that 1 wt% FLG is more appropriate for friction and wear modifiers for lithium compound grease at elevated temperatures and less suitable at ordinary temperatures. Thickener chemisorption film, FLG layering film, and tribo-reaction film consisting of FeO(OH), Fe2O3, Fe3O4, Li2O, and other oxides assist in the establishment of a lubricating boundary film on the friction interfaces lubricated with LCG containing FLG. The poor fluidity of lithium compound grease at low temperatures leads to poor dispersion of FLG, decreasing friction reduction capability. Under elevated temperature and low load condition, adding 1wt% FLG to LCG can only improve its wear-resistant property, the abrasion volume of steel plate reduced by 24.49%. Under elevated temperature and high load condition, adding 1wt% FLG to LCG can only enhance its anti-friction characteristics.. Conversely, FLG is unsuitable as an anti-friction and wear-resistant additive for LCG at low-temperature conditions.

Microstructure and mechanical properties of (CrxTi1-x)2AlC 211 MAX phases as composites through spark plasma sintering

MAX phases are intriguing materials due to their unique properties. However, each of these materials possesses its own weaknesses when subjected to service conditions. For example, while one MAX phase exhibits self-lubricating feature, it may not perform well under high load conditions. This study investigates the impact of adding chromium to Ti2AlC on microstructure and mechanical properties. Samples are prepared through ball-milling and spark plasma sintering (SPS), then analyzed using various techniques. The presence of different phases, including MAX phases (Ti2AlC and Cr2AlC), carbides (TiC and Cr7C3), and low amounts of oxides, is identified. Hardness, fractography, and wear characteristics are assessed through indentation and sliding tests. The study correlates the wear rate of each sample with experimental (H/E) and theoretical indicators (B/G), showing the production of composites with improved properties suitable for diverse applications.

Moving beyond the Aerosol Climatology of WRF-Solar: A Case Study over the North China Plain

Abstract Numerical weather prediction (NWP), when accessible, is a crucial input to short-term solar power forecasting. WRF-Solar, the first NWP model specifically designed for solar energy applications, has shown promising predictive capability. Nevertheless, few attempts have been made to investigate its performance under high aerosol loading, which attenuates incoming radiation significantly. The North China Plain is a polluted region due to industrialization, which constitutes a proper testbed for such investigation. In this paper, aerosol direct radiative effect (DRE) on three surface shortwave radiation components (i.e., global, beam, and diffuse) during five heavy pollution episodes is studied within the WRF-Solar framework. Results show that WRF-Solar overestimates instantaneous beam radiation up to 795.3 W m−2 when the aerosol DRE is not considered. Although such overestimation can be partially offset by an underestimation of the diffuse radiation of about 194.5 W m−2, the overestimation of the global radiation still reaches 160.2 W m−2. This undesirable bias can be reduced when WRF-Solar is powered by Copernicus Atmosphere Monitoring Service (CAMS) aerosol forecasts, which then translates to accuracy improvements in photovoltaic (PV) power forecasts. This work also compares the forecast performance of the CAMS-powered WRF-Solar with that of the European Centre for Medium-Range Weather Forecasts model. Under high aerosol loading conditions, the irradiance forecast accuracy generated by WRF-Solar increased by 53.2% and the PV power forecast accuracy increased by 6.8%. Significance Statement Numerical weather prediction (NWP) is the “go-to” approach for achieving high-performance day-ahead solar power forecasting. Integrating time-varying aerosol forecasts into NWP models effectively captures aerosol direct radiation effects, thereby enhancing the accuracy of solar irradiance forecasts in heavily polluted regions. This work not only quantifies the aerosol effects on global, beam, and diffuse irradiance but also reveals the physical mechanisms of irradiance-to-power conversion by constructing a model chain. Using the North China Plain as a testbed, the performance of WRF-Solar on solar power forecasting on five severe pollution days is analyzed. This version of WRF-Solar can outperform the European Centre for Medium-Range Weather Forecasts model, confirming the need for generating high spatial–temporal NWP.