Mechanism Of Performance Improvement Research Articles

Analysis of the Performance Improvement Mechanism of Foamed Rubber Asphalt Based on Micro and Macro Perspectives

Foamed rubber asphalt has attracted wide attention in cold-recycled pavement projects due to its excellent performance, strong construction performance and resource conservation, but the mechanism of its performance improvement after foaming is still unclear. In order to explore the difference in the performance of rubber asphalt before and after foaming, this study systematically analyzed the performance improvement mechanism of asphalt from nano, micro and macro perspectives. Molecular dynamics simulation results show that the density and modulus of rubber asphalt decrease after foaming. After foaming, the glass transition temperature of rubber asphalt decreased by 4.4 K, and the free volume fraction decreased by 4.7%, which indicated that its low-temperature toughness was enhanced. The simulation results also illustrate the performance enhancement mechanism of rubber asphalt. Rubber and asphalt are physically mixed and do not undergo chemical reactions. However, foaming makes the rubber particles more evenly distributed, helping to improve the toughness and fatigue properties of asphalt. Macroscopic test results show that the high-temperature performance and fatigue performance of foamed asphalt are reduced, while the low-temperature performance is improved. The molecular simulation results are consistent with the experimental results, providing a comprehensive explanation for the improvement mechanism of rubber asphalt performance.

In situ decoration of AuPd nanoparticles on MOF derived ZnO for ultra-high response and low detection limit trimethylamine detection.

Trimethylamine (TMA) is a colorless, volatile gas with a strong irritating odor. Prolonged exposure to a certain amount of TMA can cause symptoms such as dizziness, nausea and difficulty breathing, and may even be life-threatening. Therefore, effective detection of TMA is crucial. Gas sensors, due to their convenience, affordability and ability to real-time detect volatile gases including TMA, are increasingly favored. However, gas sensors based on single metal oxide materials have numerous drawbacks and may not meet practical requirements. Therefore, it is necessary to modify gas-sensitive materials to achieve sensors with higher sensitivity and selectivity at lower operating temperatures. In this research, gas-sensitive materials for detecting TMA were synthesized using liquid-phase methods. Firstly, metal-organic framework-derived ZnO nanoparticles were prepared via a co-precipitation method, followed by the in-situ reduction method to prepare ZnO modified with Au, Pd, and AuPd bimetallic nanoparticles. The experimental results revealed that when the total loading of AuPd was 2wt% and the ratio was Au:Pd=1:1, the gas-sensitive performance was enhanced significantly. The AuPd-ZnO sensor exhibited a remarkable high response of 1608.3 to 100ppm TMA at 200°C, which was approximately 140 times that of pristine ZnO (Ra/Rg=11.5, 275°C), and the optimal operating temperature was reduced by 75°C. Additionally, the sensor boasted a rapid response time (3s), and low detection limit (50ppb), high selectivity along with good long-term stability. The modified material can enable lower power consumption, increased sensitivity and enhanced stability for real-time detection of TMA. Combined with multiple characterization methods, the sensing mechanism of performance improvement was analyzed, which benefited from the electronic and chemical sensitization of Au and Pd, along with the synergistic effect of the AuPd bimetal. This research provided an effective strategy for the design of high-performance TMA gas sensors.

Optimization of Electrolyte Composition to Suppress Al Corrosion in Localized High-Concentration Electrolytes

Introduction Electrolytes with LiFSI added as lithium salt have advantages such as high thermal stability[1] and high cycle life performance at high temperatures. However, electrolytes with LiFSI have a problem of Al corrosion of a current collector of positive electrode due to the reaction of Al with FSI– and free solvent molecules[2]. To address this problem, there have been researches of suppressing Al corrosion by high-concentration electrolytes[3]. In high-concentration electrolytes, interactions between Li+, FSI– and solvents are enhanced leading to increasing ionic association and reducing free solvent molecules. On the other hand, poor rate performance with high-concentration electrolytes is true in most cases due to low ionic conductivity and high viscosity. In this study, localized high-concentration electrolytes with lower viscosity and better rate performance were investigated by diluting high-concentration electrolyte with a fluorinated ether solvent. We examined multiple ratios of electrolyte components such as solvents, a diluent, and LiFSI in localized high-concentrationelectrolytes and suppress Al corrosion by finding the ratio that enhances interactions between Li+, FSI– and the solvents. Experimental The electrolyte system consisted of the blends of 1,2-Dimethoxyethane (DME) and Ethylene carbonate (EC) as solvents, with 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) serving as a diluent. The ratio was 17:7:76 wt%, and the concentration of LiFSI ranged from 0.1 M to 1.7 M. Linear sweep voltammetry was performed to analyze the Al corrosion behavior in each electrolyte. Experiments were conducted at a temperature of 25°C, a scanning speed of 1.0 mV/s, and a scanning potential range of 3.0-5.0 V (vs. Li/Li+). An Al plate electrode was used as the working electrode, Li metal as the reference electrode, and Li metal as the counter electrode. Also, raman spectroscopy measurements were performed to analyze the solvation structure of each electrolyte. The measurements were performed at room temperature. Results and Discussion Figure 1 shows the results of linear sweep voltammetry. Sharp increases in oxidation current possibly due to Al corrosion at higher than around 4.0 V were observed at 0.5 M and 0.1 M, but not at 1.0 M or higher. To analyze the relationship between the Al corrosion and solvation structure, raman spectroscopy measurements were performed as shown in Figure2. The peaks at 0.5 M and 0.1 M were attributed to free FSI–. However, the peak shifted to a higher frequency region above 1.0 M. This is due to enhanced interactions between Li+, FSI– and the solvents, and it leads to prevention of Al corrosion. From these results, it is indicated that Al corrosion can be suppressed by controlling the solvation structure of FSI by adjusting the salt concentration. At the poster session, we will also report the results of our evaluation of Al corrosion behavior and solvation structure by changing the ratio of DME, EC, and TTE. In addition, the results of the investigation of the ratio of solvents and a diluent for high cycle life performance and low internal resistance, as well as mechanism of performance improvement will be reported by our colleague.

Optimization of Operating Conditions to Improve the Performance of Brine Electrolyzer for Minerialization of Waste Cement and Steel Slag

The most important unit in mineralization to produce nano-CaCO3 from waste inorganic materials is the electrolyzer producing both HCl and NaOH at the applied potential less than 1.5 V, because both the extraction efficiency of Ca ions from waste concrete and steel slag using 0.5M HCl and the carbonation efficiency to produce CaCO3 are almost about 100% in the mineralization process [1,2]. The nano-CaCO3 can be produced through CO2 bubbling into Ca(OH)2 slurry, which is prepared from the purified fitrate solution using 1 M NaOH produced from the electrolyzer. The impurities such as Fe, Al and Mg are removed in the purification step. One of the drawbacks of the electrolysis of NaCl is that it is very difficult to improve reaction rate, because the applied potential for the electrolyzer should be less than 1.5V to achieve the objective of CO2 mitigation. Another one is to maximize the caustic efficiency. Unfortunately, both the applied potential and caustic efficiency have a trade-off relationship. This study aims to develop a way to improve the performance of electrolyzers by optimizing operating conditions. It has been found that the applied voltage and operating temperature among others can effectively enhance the reaction rate and caustic efficiency simultaneouly. Under the optimal conditions, the reaction rate is significantly enhanced more than 2 times and the caustic efficiency more than 1.5 times compared to those obtained under standard conditions. This is because the relative permeation rate of Na+ over H+ through a Nafion membrane is elevated by increasing temperature and applied voltage. Analytical work has been conducted to reveal the mechanism of performance improvement by investigating the permeation behaviors of the ions through the Nafion membrane. It is found that the permeation rate of an ion through membrane is interfered by the presence other ions. That is, the permeation of sodium ions is significantly hindered by protons, but this interference is dramatically overcome by raising temperature and applied voltage. A long-term test more than 1500 hours is also carried out to test the stability and feasibility of the electrolyzer. In this study, we have proven that the performance of brine electrolyzer could be successfully improved by optimizing the operating conditions such as temperature and applied voltage. References Lee J., Ryu K.H., Ha H.Y., Jung K.D., and Lee J.H., J. CO2 Utilization, 37 (2020) 113.Park K.H., Lee K.R., Jo H., Park J.W. Lee J.H., Jung K.D., CO2 Utilization, in revision.

Structure regulation and performance optimization mechanism of Sr0.7Bi0.2TiO3-based energy storage ceramics based on charged defect design engineering

The linear-like relaxor ferroelectric Sr0.7Bi0.2TiO3 with regulable microstructure offers a new platform to reveal the essential mechanism of energy storage properties improvement and develop advanced pulse capacitors. Herein, Li with relatively weak volatility accompanied by Bi was introduced in Sr0.7Bi0.2TiO3 to form a charged defect and increase the maximum polarization (Pmax) while avoiding the deterioration of dielectric breakdown strength (BDS). The occupation of Li and the formation of Li-Bi defect dipole polar were analyzed using first principle calculations. A unique local superlattice induced by the lattice distortion was first observed in related systems. The Pmax was enhanced due to the increased size and number of polar structures. The breakdown behaviour and local electric field distribution were analyzed using numerical simulation. The BDS was improved due to the decreased oxygen vacancies, high thermal conductivity and enhanced electrical insulation. The excellent and stable energy storage performance was achieved in different temperatures, frequencies and cycles. Meanwhile, the optimized sample possesses excellent and stable charge–discharge properties, especially fatigue resistance (105 cycles under 25 °C and 150 °C). After the process optimization, the sample shows a higher energy storage density of 3.44 J/cm3 with a high efficiency of 93.74 % at 345 kV/cm due to the further enhanced BDS. In this work, the performance improvement mechanism was studied in-depth, providing a new strategy for optimizing linear-like lead-free relaxor ferroelectric energy storage properties.

Influence characteristic and improvement mechanism of thermal storage performance of Packed-bed thermocline tank based on high-temperature molten salt

Chloride salts and carbonates thermal energy storage (TES) have great application potential in high-temperature concentrated solar power (CSP) plants. However, their thermal storage characteristics, performance improvement mechanism and economic feasibility of application in high-temperature conditions are not clear. In this study, a transient, two-dimensional and axisymmetric model is developed for packed-bed thermocline tanks. The effects of six commonly solid fillers on thermal storage performance of NaCl-KCl-MgCl2 salt and Na2CO3-K2CO3-Li2CO3 salt at an operation temperature of 450–800 °C are simulated. The suggestions for optimizing fillers are provided combined with thermal and economic performance. Results show that high volume heat capacity and low thermal conductivity of fillers play important roles in deferring migration and weakening diffusion of thermocline, thus promoting thermal storage capacity and efficiency of tanks. Concrete and cast iron are suitable fillers for chloride salts and carbonates TES. The concrete tank is suitable for systems with strict cost control and low TES requirements. The iron tank is suitable for systems with high TES and low cost control requirements, which significantly increases effective thermal storage capacity of chloride salts by 222.1 % and considerably reduces TES cost of carbonates by 41.1 %. The results can be beneficial for high-temperature TES system of CSP plants.

Aerodynamic optimization design and experimental verification of a high-load axial flow compressor

The performance and stable operating range of compressors are critical to the efficient operation of various turbomachinery systems. This paper proposes a multi-level optimization strategy combining the uni-uniform direct free deformation method, Linux partitioned CPU accelerated parallel computing technology, multi-objective particle swarm optimization algorithm and downhill simplex algorithm, which improves design efficiency. Numerical results show that after optimization design, the average value of peak efficiency and stall margin increases. The flow mechanism of compressor performance improvement after optimization lies in the reduction of a low-velocity separation zone in stator hub region. Moreover, the experiment study confirms the reliability and accuracy of the optimization design method and found that flow instability triggering mode, propagation characteristics of the stall cell, and surge frequency are changed after optimization design. Setting a probability distribution threshold for autocorrelation coefficient and cross-correlation coefficients can be used to predict the arrival of the surge condition.

Synergistic effects of buton rock asphalt and BBOEA on the enhanced temperature resistance and flexibility of asphalt

To improve the toughness of transportation infrastructure and develop asphalt composite materials with both elasticity and toughness, this paper prepared Buton rock asphalt (BRA)/Bis[2-(2-butoxyethoxy)ethyl] adipate BBOEA composite modified asphalt. The evolution of high and low-temperature performance of the composite modified asphalt was explored through key asphalt indicators, dynamic shear rheology, and bending beam rheometer (BBR) tests. The performance improvement mechanism of the asphalt was investigated using Fourier transform infrared spectroscopy (FTIR). The addition of Buton rock asphalt effectively improved the high-temperature performance of the asphalt, raising the high-temperature PG grade from 64 to 70 and enhancing resistance to permanent deformation. The inclusion of 1.5 % BBOEA further enhanced low-temperature performance, reducing the stiffness modulus of BRA modified asphalt from 365 MPa to 260 MPa, a decrease of 26.9 %. This improvement is attributed to the polar adipate functional groups in BBOEA, which promote hydrogen bonding and dipole–dipole interactions with polar groups in the resins, reducing micelle size and asphalt rigidity. With the high-temperature performance remaining robust and low-temperature flexibility and strain relaxation greatly improved, the optimal BBOEA content is recommended at 1.5 % of the asphalt mass.

Impact of titanium modification on the performance improvement and phase change mechanism of ZnSb thin film

Phase change memory has emerged as a promising option for neuro-inspired and data-intensive AI applications, attracting significant attention from the semiconductor field recently. The performance of the device relies on the phase change material, aiming for enhanced thermal stability along with low power consumption. Nanocomposite ZnSb thin films with titanium dopant were prepared and their crystallization properties and mechanisms were investigated. Compared to pure ZnSb material, the addition of titanium can significantly enhance the temperature of crystallization and the 10-year data retention ability, both of which surpassing 16 °C. The obvious enhancement in thermal stability may be ascribed to the ionic bond formation between titanium and antimony elements, as indicated by differential charge calculations. Also, phase change memory cells with a diameter of 190 nm were fabricated using standard CMOS technology. The Ti-doped ZnSb thin film demonstrates rapid crystallization and amorphization within 50 ns while consuming low power at approximately 1.5 × 10−10 J. The decrease in power consumption may stem from the increase in band gap energy and a decrease in electrical conductivity, as confirmed by first-principles calculations. Both experimental and theoretical results prove that titanium doping can remarkably improve the physical properties of ZnSb thin film, facilitating the exploration and design of novel phase change materials with high thermal stability, low power consumption, as well as fast switching speed.

Microstructure and mechanical properties of textured high‐entropy M₄AlC₃/Al₂O₃ (M = Ti, V, Mo, Nb, Ta) composites

AbstractHigh‐performance MAX phase‐based composites were developed to overcome the inherent low hardness and low strength of MAX phases by combining lattice distortion‐induced strengthening, texture strengthening, and second‐phase particle strengthening. Textured high‐entropy M4AlC3/Al2O3 (M = Ti, V, Mo, Nb, Ta) composites with different Al2O3 contents were prepared using spark plasma sintering at 1350°C for 70 min. The microstructures of all samples with different compositions were characterized in detail. It was found that as the Al2O3 content increased, the grain size of the high‐entropy M4AlC3 phase gradually decreased, and the aggregation of Al2O3 became more severe. Based on this, the density, hardness, strength, and fracture toughness of all composites were tested. The results indicate that all textured composites exhibit significant anisotropy in their properties, with the high‐entropy M4AlC3/15 vol%Al2O3 composite showing the best overall performance. Additionally, the mechanism of performance improvement was systematically discussed. This work provides an important reference for the subsequent preparation of high‐performance MAX phase‐based composites.

Study on short fiber reinforcement mechanism for mechanical performance improvement of 3D‐printed short‐continuous carbon fiber reinforced thermoplastic composites

Abstract3D printing of continuous carbon fiber reinforced thermoplastic (C‐CFRTP) composites is a promising fabricating process to achieve complex lightweight structures within a short time; nevertheless, low mechanical performance between printed layers is always a limitation. Adding short carbon fibers during C‐CFRTP fabrication could achieve short‐continuous carbon fiber reinforced thermoplastic (S/C‐CFRTP) composites with enhanced mechanical properties. However, the underlying reinforcement mechanism is not well understood, which hinders the optimization of 3D printing process for S/C‐CFRTP. This paper investigates reinforcing behavior of short carbon fibers and impregnation behavior of the matrix (short carbon fiber reinforced PA6) under various 3D printing conditions. The results indicate that promoting both reinforcing and impregnation behaviors during S/C‐CFRTP 3D printing can improve mechanical performance. As short carbon fiber content increases, the mechanical performance initially experiences enhancement caused by the reinforcing behavior of short fibers, followed by a decline attributed to the insufficient impregnation of the molten matrix. Higher nozzle temperatures facilitate the impregnation behavior of the molten matrix, resulting in superior mechanical performance. Moreover, by leveraging the reinforcement mechanism, the optimal parameter combination is proposed to improve tensile, flexural, and interlaminar shear strengths of the 3D‐printed S/C‐CFRTP to approximately 368.27, 319.80, and 20.09 MPa, respectively.Highlights Reinforcement mechanism is revealed by reinforcing and impregnation behaviors. Short carbon fiber content affects both reinforcing and impregnation behaviors. Beyond 15 wt%, short carbon fiber content shows adverse effects on performance. High nozzle temperature promotes impregnation behavior to improve performance. Optimal parameters raise 19.8% tensile, 39.9% flexural and 161.2% shear strength.

Cementing Mechanism of MICP-Treated Mortar and Performance Improvement by Innovative Molds

Cementing Mechanism of MICP-Treated Mortar and Performance Improvement by Innovative Molds

Novel tri-solvent amines absorption for flue gas CO2 capture: Efficient absorption and regeneration with low energy consumption

Blended amine scrubbing is considered as a promising alternative to the monoamine scrubbing process due to the potential for enhanced CO2 capture efficiency and reduced energy consumption. However, striking a balance between absorption rate and regeneration energy consumption in blended amine systems by establishing suitable interactions between activated amines and proton-acceptor amines remains a significant challenge. In this study, a novel blended amine system, involving tertiary amine diethanolamine (DEEA) as the main agent and several monoamines as promoters, was first proposed to achieve highly effective CO2 capture. The designed tri-solvent amine system of DEEA combined with piperazine (PZ) and 4-amino-1-methylpiperidine (PD) (denoted as DEEA + PZ + PD) exhibited exceptional CO2 loading (0.988 mol CO2/mol amine), superior cyclic capacity (0.788 mol CO2/mol amine), and reduced regeneration heat duty (2.14 GJ/t), surpassing monoethanolamine (MEA) by 79.6 %, 277 %, and decreasing by 43.7 %, respectively. Furthermore, the performance improvement mechanism of DEEA + PZ + PD was systematically elucidated, showcasing the swift CO2 absorption facilitated by PD or PZ in the initial reaction phase, and the subsequent formation of bicarbonate from PDCOO− and DEEA in the later stage, enhancing CO2 absorption capacity. The predominant reaction products, bicarbonate and unstable carbamate (PZ(COO−)2, PDCOO−), contribute to the high regeneration efficiency and minimal energy consumption during regeneration for DEEA + PZ + PD. Consequently, this facilely prepared tri-solvent amine system, characterized by high capture efficiency and low energy consumption, holds promise for achieving carbon–neutral operations in coal-fired power plants.

Analyzing the mechanism of performance improvement in LiNi0.8Co0.1Mn0.1O2 through coating with LiNbO3 fast ion conductor

The high-nickel cathode LiNi0.8Co0.1Mn0.1O2 (NCM811), a material already commercialized, faces a critical challenge in its diminished stability, leading to a decline in battery performance. This study addresses this issue by employing LiNbO3 as a fast ion conductor with varying concentrations to enhance the performance of the NCM811 material. Particularly noteworthy is the optimal performance observed with a 3% LiNbO3 coating, where the NCM811 exhibits a capacity retention of 87.10% after 200 cycles at 1 C, and a discharge capacity of 160 mAh•g−1 at a 5 C rate, surpassing the Pristine's 69.57% cycle retention and 139 mAh•g−1 at 5 C. Density Functional Theory (DFT) calculations reveal that the LiNbO3 coating not only reduces the migration barrier for Li+ within the NCM811 but also lowers the migration barrier for Li+ from the NCM811 layer to the LiNbO3 layer. Theoretical calculations further unveil that the binding energy between NCM811 and the byproduct HF in the electrolyte is lower than the binding energy between LiNbO3 surface and HF, confirming the effective inhibition of HF corrosion by the LiNbO3 layer. This work provides an in-depth analysis of the mechanism behind the improved performance of NCM811 materials through surface coating with LiNbO3.

Ultrathin layer TAFC on BiVO4 with ligand-to-metal charge transfer enhances built-in electric field for boosting photoelectrochemical water oxidation

To reveal the mechanism of charge transfer between interfaces of BiVO4-based heterogeneous materials in photoelectrochemical water splitting system, the cocatalyst was grown in situ using tannic acid (TA) as a ligand and Fe and Co ions as metal centers (TAFC), and then uniformly and ultra-thinly coated on BiVO4 to form photoanodes. The results show that the BiVO4/TAFC achieves a superior photocurrent density (4.97 mA cm−2 at 1.23 VRHE). The charge separation and charge injection efficiencies were also significantly higher, 82.0 % and 78.9 %, respectively. From XPS, UPS, KPFM, and density functional theory calculations, Ligand-to-metal charge transfer (LMCT) acts as an electron transport highway in TAFC ultrathin layer to promote the concentration of electrons towards metal center, leading to an increase in the work function, which enhances the built-in electric field and further improves the charge transport. This study demonstrated that the LMCT pathway on TA-metal complexes enhances the built-in electric field in BiVO4/TAFC to promote charge transport and thus enhance water oxidation, providing a new understanding of the performance improvement mechanism for the surface-modified composite photoanodes.

Rational design improves both thermostability and activity of a new D-tagatose 3-epimerase from Kroppenstedtia eburnean to produce D-allulose

D-allulose is a naturally occurring rare sugar and beneficial to human health. However, the efficient biosynthesis of D-allulose remains a challenge. Here, we mined a new D-tagatose 3-epimerase from Kroppenstedtia eburnean (KeDt3e) with high catalytic efficiency. Initially, crucial factors contributing to the low conversion of KeDt3e were identified through crystal structure analysis, density functional theory calculations (DFT), and molecular dynamics (MD) simulations. Subsequently, based on the mechanism, combining restructuring the flexible region, proline substitution based onconsensus sequence analysis, introducing disulfide bonds, and grafting properties, and reshaping the active center, the optimal mutant M5 of KeDt3e was obtained with enhanced thermostability and activity. The optimal mutant M5 exhibited an enzyme activity of 130.8 U/mg, representing a 1.2-fold increase; Tm value increased from 52.7 °C to 71.2 °C; and half-life at 55 °C extended to 273.7 min, representing a 58.2-fold improvement, and the detailed mechanism of performance improvement was analyzed. Finally, by screening the ribosome-binding site (RBS) of the optimal mutant M5 recombinant bacterium (G01), the engineered strain G08 with higher expression levels was obtained. The engineered strain G08 catalyzed 500 g/L D-fructose to produce 172.4 g/L D-allulose, with a conversion of 34.4% in 0.5 h and productivity of 344.8 g/L/h on a 1 L scale. This study presents a promising approach for industrial-scale production of D-allulose.

Rational Design of Salmonella typhi Acid Phosphatase for Efficient Production of Pyridoxal 5'-Phosphate.

Pyridoxal 5'-phosphate (PLP) is highly valuable in food and medicine. However, achieving the efficient biosynthesis of PLP remains challenging. Here, a salvage pathway using acid phosphatase from Salmonella typhi (StAPase) and pyridoxine oxidase from Escherichia coli (EcPNPO) as pathway enzymes was established for the first time to synthesize PLP from pyridoxine (PN) and pyrophosphate (PPi). StAPase was identified as a rate-limiting enzyme. Two protein modification strategies were developed based on the PN phosphorylation mechanism: (1) improving the binding of PN into StAPase and (2) enhancing the hydrophobicity of StAPase's substrate binding pocket. The kcat/Km of optimal mutant M7 was 4.9 times higher than that of the wild type. The detailed mechanism of performance improvement was analyzed. Under the catalysis of M7 and EcPNPO, a PLP high-yielding strain of 14.5 ± 0.55 g/L was engineered with a productivity of 1.0 ± 0.02 g/(L h) (the highest to date). The study suggests a promising method for industrial-scale PLP production.

Femtosecond laser fabrication of 3D vertically aligned micro-pore network on thick-film Li4Ti5O12 electrode for high-performance lithium storage

The development of energy storage devices with high energy density relies heavily on thick film electrodes, but it is challenging due to the limited ion transport kinetics inherent in thick electrodes. Here, we report on the preparation of a directional vertical array of micro-porous transport networks on LTO electrodes using a femtosecond laser processing strategy, enabling directional ion rapid transport and achieving good electrochemical performance in thick film electrodes. Various three-dimensional (3D) vertically aligned micro-pore networks are innovatively designed, and the structure, kinetics characteristics, and electrochemical performance of the prepared ion transport channels are analyzed and discussed by multiple characterization and testing methods. Furthermore, the rational mechanisms of electrode performance improvement are studied experimentally and simulated from two aspects of structural mechanics and transmission kinetics. The ion diffusion coefficient, rate performance at 60 C, and electrode interface area of the laser-optimized 60-15% micro-porous transport network electrodes increase by 25.2 times, 2.2 times, and 2.15 times, respectively than those of untreated electrodes. Therefore, the preparation of 3D micro-porous transport networks by femtosecond laser on ultra-thick electrodes is a feasible way to develop high-energy batteries. In addition, the unique micro-porous transport network structure can be widely extended to design and explore other high-performance energy materials.

HRM practices, organizational learning and organizational performance: evidence from the big four financial services in France

PurposeThis paper aims to examine the mediation effect of organizational learning on the link between human resource management (HRM) practices and organizational performance in some Big4 financial services companies.Design/methodology/approachThe quantitative methodology was chosen for this research, using resource theory and knowledge-based approach to explain the relationship between latent variables. A sample of 403 HR employees and managers of the companies under study in France was selected in 2022. Structural equations modeling was used based on the Spss-Amos program to test the research hypotheses.FindingsThe results revealed that organizational learning played a mediating role between HRM practices (hiring, training, motivation and decision-making) and organizational performance and that learning enabled the performance of workers to improve and achieve competitive advantages in this field.Research limitations/implicationsThe sample was based on four international companies working in the field of financial services and consulting and providing their services within France, which may affect the generalisability of the results and limit them to the studied sector.Practical implicationsThe contribution of the study is to improve the awareness of administrators, decision makers and company employees of the importance of organizational learning for companies, and to stimulate motivation to learn and exchange knowledge in a constructive way that enhances organizational performance. Working on organizational culture change through HRM-practices-based learning as an effective mechanism for organizational performance improvement is one implication. These practises influence cadres' attitudes toward their work, which improves their performance.Social implicationsWorking on organizational culture change through HRM-practices-based learning as an effective mechanism for organizational performance improvement is one implication. These practises influence cadres' attitudes toward their work, which improves their performance.Originality/valueThis study seeks to provide cadres and executives with an in-depth analysis of HRM and organizational learning, which, through its integration of these attributes, can contribute to the earning of knowledge-based competitive advantage and achieve superior and sustainable performance.

Field synergy analysis on thermal-hydraulic behavior of phase change slurry in porous microchannel heat sink with graded porosity configuration

In this study, a novel design of porous microchannel heat sink (MCHS) with graded porosity configuration is proposed in the hope of attaining lower flow and thermal resistances than constant porosity (CP) configuration. The efficacy of new scheme is validated by utilizing a three-dimensional solid-fluid conjugate model based on the finite volume method, which considers the flow and heat transfer of microencapsulated phase change material slurry (MPCMS) inside the porous fins. It is reported that the thermal performance of porous MCHS with constant and graded porosity configurations is significantly better than that of non-porous MCHS. The feasibility of new design is verified by comparing the hydrothermal behavior of multiple graded porosity MCHSs and CP configuration for different fin designs (involving the number of graded equidistant fins N, graded length ratio R, and fin-to-pitch width ratio β) and operating conditions (including Reynolds number Re, mass fraction cm, and inlet velocity uin). The comprehensive performance improvement mechanism of MPCMS in graded porosity microchannels is discussed through the analysis of flow and thermal details, field synergy angle (θ) and field synergy number (Fc), and the overall performance of new design is evaluated by performance evaluation factor (PEF). Results indicate that the six types of porous MCHS with stepwise varying porosity exhibit lower thermal resistance than CP mode, and better thermal behavior and larger PEF can be obtained at N = 2 and β = 0.7. Smaller and larger R should be chosen for stepwise increasing porosity (SIP) and stepwise decreasing porosity (SDP) modes, respectively, to achieve higher heat transfer enhancement while avoiding greater friction losses. The Fc value of porous MCHS with various porosity configurations is about two orders of magnitude less than 1 and shows a monotonically reducing trend with Re, and the synergistic effect deteriorates at high Re. Compared to the CP mode, a low-θ “drift” toward the low porosity region of porous fin occurs within the graded porosity MCHS, which decreases and increases in the downstream and upstream directions of the “drift”, respectively. Among the novel MCHS designs, the z-directional SIP mode acquires the best overall performance due to the excellent synergy between the velocity and temperature fields, and its PEF consistently exceeds 1.13 and reaches up to 1.33. Generally speaking, the fin porosity of graded porosity MCHS near the channel cavity, channel top, and channel inlet should be greater for superior comprehensive performance.