Fluctuation Range Research Articles

Influence of fracture parameters on hydraulic shear seepage characteristics of granite

To reveal the influence mechanism of different fracture parameters on the permeability characteristics of hot dry rock after hydraulic shear. The self-made high temperature true triaxial hydraulic shear test device and rock roughness profile tester were used. The granite in Daqing area of Songliao Basin is taken as the research object. The prefabricated fractured granite is subjected to high-temperature treatment. The geological characteristics of different geothermal reservoirs are simulated by changing the three-dimensional stress. The roughness coefficient of the fracture surface is used to characterize the variation characteristics of fracture before and after hydraulic shear. The influence of different fracture angles and roughness on the permeability of granite after hydraulic shear was tested. Combined with numerical simulation, the relationship between fracture parameters and geothermal mining performance is analyzed. The results show that the maximum water injection pressure of hydraulic shear decreases with the increase of fracture angle by quadratic polynomial law and increases with the increase of fracture roughness by quadratic polynomial law. The variation of fracture surface roughness coefficient fluctuates within 0–2 with the increase of volume stress before and after hydraulic shearing. The variation of fracture surface roughness coefficient increases linearly with the increase of water injection flow rate and increases with the increase of water injection time, and there is a fluctuation range of 0.38–0.44. After hydraulic shear, the permeability of granite increases first and then decreases with the increase of fracture angle. When the fracture angle is 15°, the permeability has the maximum value. The permeability increases with the increase of fracture surface roughness. The numerical simulation results show that the high fracture opening (15 mm), high fracture number, and high fracture penetration performance significantly improve the geothermal mining efficiency.

Experimental study and theoretical analysis on tensile properties of concrete reinforced with different polymer-impregnated basalt textiles

Textile-reinforced concrete (TRC) has become a new material for strengthening and constructing structures. The mechanical properties of TRC are significantly influenced by the polymer impregnation of textile. However, the influencing mechanisms of different polymers on the mechanical properties of TRC remain unclear. In this study, the effects of polymer impregnations on tensile behavior of basalt textile reinforced concrete (BTRC) were investigated. The results showed that the epoxy resin-impregnated basalt textile outperformed other polymer-impregnated textiles in improving the tensile properties of concrete, exhibiting an ultimate stress 48%–110% higher than other samples. Increasing the textile layers number from 1 to 3 improved the ultimate stress and energy consumption, with the most notable improvements observed at 146% and 173%, respectively, for samples reinforced with epoxy resin-impregnated textiles. However, the increased textile layers reduced the ultimate strain and fiber strength utilization efficiency due to the inconsistent stress transfer among multi-layer textiles. Only epoxy resin-impregnated textiles reinforced samples exhibited a complete three-stage variation in the tensile stress-strain curve, where the stress fluctuations in the post-cracking stage were attributed to the multiple concrete cracks. In contrast, other polymer-impregnated textile-reinforced concrete samples experienced stress fluctuations in post-cracking stage primarily due to the textile slippage, inconsistent textile fractures, and propagation of initial crack. Furthermore, the epoxy resin-impregnated textiles' superior tensile strength and excellent bond with concrete contributed to reduced stress fluctuation range and smaller stress drop after initial cracking. Finally, an optimized tensile model with high accuracy was proposed to describe the tensile response of polymer-impregnated basalt textile reinforced concrete.

Helically Coiled Tube Flocculators in Water Clarification Systems: Optimal Length Evaluation and Process Efficiency Probabilistic Analysis

New sustainable technologies have been explored as potential solutions to address the global issue of water scarcity by enhancing water treatment processes. In this context, an innovative coagulation/flocculation unit known as the helically coiled tube flocculator (HCTF) has emerged, offering notable advantages such as high process efficiency, short detention time, and cost-effectiveness compared to conventional hydraulic units. The HCTF harnesses its flow energy to disperse coagulation/flocculation agents and facilitate the formation of flocs through collisions between destabilized particles. This paper introduces an assessment of the process efficiency, geometric properties, and hydraulic characteristics of an alternative and sustainable water clarification system incorporating an HCTF, with the aim of determining its optimal length. In HCTFs, the flocculator’s length (referred to as L) can exert a significant influence on process efficiency, necessitating a comprehensive evaluation of this parameter for the rational design of such units. To accomplish this, the paper scrutinizes physical experimental findings from previous research articles, which are related to the efficiency of flocculation (indirectly estimated by analyzing turbidity removal efficiency). Additionally, it examines the geometric and hydraulic attributes across 48 distinct variations of HCTFs. This study culminates in the development of a model for determining the optimal length for HCTFs. Furthermore, it includes a probabilistic assessment that establishes a connection between the optimal length and other parameters involved in the clarification process—whether deterministic or probabilistic—and their impact on the final process efficiency, all with a 90% confidence level. This paper stands out by pioneering the determination of the optimal length of HCTFs, filling a gap in the existing literature, which previously only mentioned the importance of this parameter in process efficiency without providing a predictive model. The results highlight the robustness of the proposed alternative clarification system. Even in scenarios with substantial variations in dimensional hydraulic parameters (such as a worst-case relative standard deviation of 20%), the process efficiency fluctuations range between 1.3% and 5.2%. These outcomes lend support to the adoption of such alternative water clarification systems. They also underscore the potential of probabilistic evaluation as a valuable tool for investigating novel water and wastewater treatment units and enhancing existing ones.

Development of a distributed group control strategy for pumping well groups connected by multisource DC microgrids

Due to the alternating loads on pumping units and the integration of new energy sources, multisource DC microgrid pumping unit well groups experience increased fluctuations in voltage and power as well as superimposed peak and valley values. This work presents a distributed control strategy for pumping unit well groups on a multisource DC microgrid based on the weighted moving average algorithm. A centralized control program is implanted in the RTU of the single-well controller of each pumping unit, and communication with each well is realized via SCADA and multicast communication, resulting in a distributed well group system. The real-time power values of the pumping well group are calculated by grouping the power values, and each group is weighted using the total power fluctuation threshold of the well group as the control target. Then, a weighted moving average algorithm is used to predict the next power value and form a table of predicted real-time power spectra. According to the power values in the community power spectrum table, the inverter frequency is proportionally adjusted downwards to reach the power peak before deceleration; after the power peak is crossed, the frequency is increased in the same way to reach the power valley before acceleration. Finally, the peak and valley power values of the bus system level off and further learn to reach the set impulse; ultimately, a stable impulse is formed. In laboratory testing and field application in the Shengli Oilfield XIN-11 block, the group control software module effectively suppressed the active power peak and valley values and voltage fluctuations of the bus system, the active power fluctuation rate range decreased by more than 70%, and the DC bus voltage fluctuation range decreased by more than 80%; moreover, the active power decreased by approximately 6% without additional hardware costs.

Variations in the characteristics of low-voltage logic gates based on vertical silicon nanotransistors with a conical channel

The issues of numerical simulation of fluctuations in the electro-physical characteristics of low-voltage logic gates based on silicon vertical nanotransistors with a surrounding gate with a conical geometry are discussed. Instrumentation and technological models of n- and p-types of conductivity of conical nanotransistors have been developed for the case when the conical working area is set as follows. On the source side, for a large diameter, the condition for suppressing short-channel effects is not fulfilled, and on the drain side, for a small diameter, it is fulfilled. Such transistor structures in the control voltage range from 0 to 0.6 V are characterized by a higher transistor current, a low leakage current and a slope of the subthreshold characteristic close to the theoretical limit. Prototypes of transistors with optimal parameters for the synthesis of logic gates with a gate length of 25 nm and a working area diameter ratio of 8.5/10 nm have been selected. The fluctuation range of the drain current is distributed according to the normal law for both types of transistors with an average of 12.25 µA for the n-type and 6.5 µA for the p-type and a standard deviation of 19.3. The total spread is 3.06 µA and 1.45 µA, or 25% and 22%, respectively. To offset the influence of the considered mechanisms, it is recommended to limit the level of doping of the drain/source regions and use relatively large cross-sections of the working area from the range of possible ones. This will ensure stable electro-physical characteristics of transistors with high parry of short-channel effects. An instrument-technological model of an inverter based on vertically arranged n- and p-type transistors with an optimized diameter ratio has been developed. Variations of electro-physical characteristics in the range of control voltages 0...0.6 V and a clock frequency of 20 GHz are numerically investigated. In all cases, the prototypes demonstrate picosecond delays and low power consumption. The valve model predicts a general fluctuation of switching times of 18% at average values of 1.6 and 0.8 ps, respectively, active power of 16% at an average value of 0.2 µW and static power of 11% at an average value of 0.7 pW. The results of the study can be used in the design of digital circuits to expand the SOA zone.

Ледовитость российских арктических морей трассы Северного морского пути в современный климатический период

The paper considers the ice cover in the Arctic seas of the Northern Sea Route (NSR): Kara, Laptev, East Siberian and Chukchi since 1946. A comparison of the long-term course of integral average annual air temperature anomalies and seasonal average ice cover anomalies allows identifying a year 2005, starting from which the sea ice cover sharply decreases in a good agreement with the increase and accumulation of positive air temperature anomalies. The researchers reveal that the average level of ice cover has decreased by 1.7 times since 2005, however, the values of the range of fluctuations and standard deviation have remained almost unchanged, i.e. ice cover fluctuates in the same range, but at a lower average level. The main shipping routes are cleared about three decades earlier. The repeatability of complete cleansing of the seas has increased to 60—90%.

3D rolling contact finite element analysis of high-speed railway turnout considering ratchetting effect

The present work introduces a three-dimensional finite element model for the wheel-turnout-sleeper system, incorporating a cyclic constitutive model that accurately captures the nonlinear hardening behavior of rail steel under cyclic loadings. At the same time, a mixed implicit-explicit finite element method is employed to investigate the transient rolling contact behavior of wheel-turnout. Through dynamic analysis, the transient rolling contact status of the wheel-turnout, stress and strain responses of the turnout, and wheel-rail forces are investigated under varying crossing speeds and number of cycles. It is found that during the wheelset crossing, the contact stress remains relatively stable on the stock rail, and multi-point contact occurs at the wing rail and long point rail, and the contact stress on the surface of the long point rail is more significant. With an increase in crossing speed in the same cycle, there is a gradual rise in contact stress on the long point rail face. At the same crossing speed, with the increase in the number of cycles, the contact position between the wheelset and the long point rail gradually moves back, and the top width of the contact position gradually expands. Meanwhile, the fluctuation range of vertical displacement of the wheel center diminishes, and the wheel flange moves away from the long point rail. Additionally, a progressive accumulation of ratcheting strain is observed on the rail, and the ratcheting strain on the long point rail significantly exceeds that on the stock rail. The research results will help to provide a reference for the optimization and design of the critical cross-section profile of the long point rail and will have guiding significance for the maintenance and repair of turnouts.

Advancing energy storage capabilities in 0.7BNST(1-x)-0.3BLMNx lead-free dielectric ceramic materials

Lead-free ferroelectric ceramics with a composition of 0.7(Bi0.5Na0.5)0.7Sr0.3Ti(1-x)O3-0.3Ba0.94La0.04(Mg1/3Nb2/3)xO3 (abbreviated as 0.7BNST(1-x)-0.3BL(MN)x, 0 ≤ x ≤ 0.12) were prepared using solid-phase sintering method, involving co-substituting at A and B sites. High recoverable energy density (Wrec) of 3.54 J/cm3 and energy efficiency (η) 85.49% are achieved at an electric field of 270 kV/cm. Furthermore, these ceramics exhibited excellent temperature and cycle stability at 120 kV/cm (within 25 °C–150 °C, Wrec fluctuation range <14 %; under 1∼106 cycles, the Wrec fluctuation range <5 %). In terms of dielectric performance, they exhibited a high dielectric constant (εr∼4540), an extremely low dielectric loss tanδ of <0.04 (30 °C–300 °C), and good temperature stability with Δε/ε150 °C ≤ ±15 % (−19.5 °C–233.4 °C). During the charging and discharging process, these ceramics demonstrated a high energy density (Wd) of 1.2 J/cm3, a power density (PD) of 61.7 MW/cm3, and an extremely short discharge time (t0.9) of approximately ∼0.11 μs＀ This study has improved the dielectric energy storage performance of BNT-based lead-free piezoelectric ceramics, making them suitable for use in pulse power devices.

An investigation of the effect of stratification stability and saltation sand flux on the anisotropy of atmospheric surface layer wall turbulence

In the atmospheric surface layer (ASL), the anisotropic characteristics of turbulence become more complex due to the strong influence of heat flux and particle motion. In this paper, the effects of stratification stability and total saltation sand flux on turbulent anisotropy of ASL wall turbulence are systematically analyzed by using high-frequency 3D velocity, temperature, and saltation sand flux measured in the field. Our results show that the temperature gradient intensifies the spanwise turbulent motion and enhances the vertical motion asymmetry. Although the buoyancy-driven turbulence enhances the spanwise variation, the momentum transfer mode between the streamwise–vertical and spanwise–vertical does not change. With the increase in instability, the large-scale motions (LSM) of the spanwise velocity may be destroyed and more spanwise small-scale motions (SSM) formed. In addition, saltation increases the sharpness, randomness, and extreme frequency of spanwise velocity distribution, but does not change the momentum transfer mode. Saltation may enlarge the fluctuation range and scale of the spanwise velocity, but may not be the main factor affecting the anisotropy of SSM. These results can deepen people's understanding of wind-blown sand movement and turbulence properties in ASL, and provides empirical data and insights that can significantly contribute to the development and refinement of turbulence models, particularly those that need to account for the complex interplay between stratification stability, saltation sand flux, and turbulence anisotropy.

Research on the heat–humidity coupling transfer model of the CRTS Ⅱ type track slab and its characteristics

After operation for more than 10 years, CRTSⅡtype track slab structures have developed interlayer diseases in continuous extreme high-temperature environments, which are dominated by track slab-CA mortar layer cracking. To reveal the formation mechanism of track slab-CA mortar layer cracking under complicated operation conditions, a heat–humidity coupling transfer model, which is utilized to analyze track slab deformation, was developed. Furthermore, to enhance the precision of the model, we investigated the variation law that regulates relevant parameters of concrete materials with respect to temperature and humidity. Moreover, a testing apparatus was established to validate the accuracy of the transfer model under natural conditions. The analysis revealed that the maximum temperature error in the track slab was 3.33 K, and that the maximum error of relative humidity (RH) was 6.04 %. The distribution characteristics of temperature and humidity fields in the track slab during 10 consecutive rainless days under different seasonal climates in a hot-summer and cold-winter zone (Hangzhou) in China were calculated and analyzed using COMSOL Multiphysics® software. The results indicated that in the distribution of the summer temperature field, the maximum negative temperature gradient could attain -48.67 K/m, and that the maximum positive temperature gradient could attain 76.37 K/m. Moreover, RH values at 10 mm, 20 mm, 30 mm, and 40 mm decreased by 30.85 %, 15.51 %, 9.17 %, and 5.9 %, respectively. In a year, a higher track slab temperature, a greater temperature fluctuation range, and more apparent positive and negative temperature gradients were observed during summer, and the influencing depth of water also attained the maximum value during summer.

The Effects of Ambient Temperature and Atmospheric Humidity on the Diffusion Dynamics of Hydrogen Fluoride Gas Leakage Based on the Computational Fluid Dynamics Method.

In order to investigate the impact of environmental temperature and atmospheric humidity on the leakage and diffusion of hydrogen fluoride (HF) gas, this study focused on the real scenario of an HF chemical industrial park. Based on the actual dispersion scenario of HF gas, a proportionally scaled-down experimental platform for HF gas leakage was established to validate the accuracy and feasibility of numerical simulations under complex conditions. Using the validated model, the study calculated the complex scenarios of HF leakage and diffusion within the temperature range of 293 K to 313 K and the humidity range of 0% to 100%. The simulation results indicated that different environmental temperatures had a relatively small impact on the hazardous areas (the lethal area, severe injury area, light injury area, and maximum allowable concentration (MAC) area) formed by HF gas leakage. At 600 s of dispersion, the fluctuation range of hazardous area sizes under different temperature conditions was between 3.11% and 13.07%. In contrast to environmental temperature, atmospheric relative humidity had a more significant impact on the dispersion trend of HF leakage. Different relative humidity levels mainly affected the areas of the lethal zone, light injury zone, and MAC zone. When HF continued to leak and disperse for 600 s, compared to 0% relative humidity, 100% relative humidity reduced the lethal area by 35.7%, while increasing the light injury area and MAC area by 27.26% and 111.6%, respectively. The impact on the severe injury area was relatively small, decreasing by 1.68%. The results of this study are crucial for understanding the dispersion patterns of HF gas under different temperature and humidity conditions.

Potential marker subset of blood-circulating cytokines on hematopoietic progenitor-to-Th1 pathway in COVID-19.

In this study, we analyzed a relatively large subset of proteins, including 109 kinds of blood-circulating cytokines, and precisely described a cytokine storm in the expression level and the range of fluctuations during hospitalization for COVID-19. Of the proteins analyzed in COVID-19, approximately 70% were detected with Bonferroni-corrected significant differences in comparison with disease severity, clinical outcome, long-term hospitalization, and disease progression and recovery. Specifically, IP-10, sTNF-R1, sTNF-R2, sCD30, sCD163, HGF, SCYB16, IL-16, MIG, SDF-1, and fractalkine were found to be major components of the COVID-19 cytokine storm. Moreover, the 11 cytokines (i.e., SDF-1, SCYB16, sCD30, IL-11, IL-18, IL-8, IFN-γ, TNF-α, sTNF-R2, M-CSF, and I-309) were associated with the infection, mortality, disease progression and recovery, and long-term hospitalization. Increased expression of these cytokines could be explained in sequential pathways from hematopoietic progenitor cell differentiation to Th1-derived hyperinflammation in COVID-19, which might also develop a novel strategy for COVID-19 therapy with recombinant interleukins and anti-chemokine drugs.

Experimental study of energy‑absorbing and support characteristics of glass microsphere-filled steel tube columns under uniaxial compression.

An innovative energy-absorbing and bearing structure was proposed, which incorporated the coupling of glass microspheres with a metal tube. Glass microsphere-filled steel tube (GMFST) column, consisting of external steel tube and inner glass microspheres, was expected to give full play to the energy-absorbing and load-bearing capacities of the particle while restricting particle flow from collapsing, thereby enhancing the overall structural strength. Four groups of steel tubes and the GMFST specimens were designed and subjected to axial compression tests at four different loading rates to investigate the performance of the structure. These tests aimed to analyze the deformation mode, mechanical response, and energy absorption capacity of the GMFST columns under quasi-static to low-speed compression conditions. The results indicated that the deformation process and failure mode of GMFST columns were similar to those of hollow steel tubes, albeit with a different post-buckling mode. Filling the steel tubes with glass microspheres reduced the load fluctuation range, moderated load-displacement curves, and exhibited a strain rate strengthening effect. The GMFST columns demonstrated superior energy absorption capacity, with significant increases in crush force efficiency, the averaged crush force, and the total absorbed energy, particularly in terms of subsequent support capacity. The load-increasing reinforcement properties enabled GMFST columns to overcome the limitations associated with the unstable post-buckling path of energy‑absorbing damping structure, exhibiting outstanding load-bearing performance and stability in the later stages. The results provided valuable guidelines for designing and engineering high-performance GMFST columns, serving as a new type of energy-absorbing and supporting structure.

Optimization of Load Distribution Method for Hydropower Units Based on Output Fluctuation Constraint and Double-Layer Nested Model

During the load distribution of hydropower units, the frequent crossing of vibration zones as well as large output fluctuations affect the stability of the power station. A multi-objective double-layer intelligent nesting model that considers the constraint of the output fluctuation of units is proposed to address these problems. The nonlinear constraint unit commitment optimization model layer is built based on outer dynamic programming, and the load distribution optimization model layer is constructed based on the improved biogeography-based optimization algorithm. Simultaneously, the unit output fluctuation constraint is established based on whether the unit combination changes in order to limit the unit output fluctuation. The results of this model indicate that compared with traditional load allocation models, the application of the method proposed in this paper can reduce the fluctuation range of unit output by 85.01%. In addition, except for the inevitable vibration zone crossings during startup and shutdown processes, the unit does not cross the vibration zone during operation, which greatly improves the unit’s vibration isolation and optimization capabilities. The multi-objective double-layer intelligent nested model proposed in this paper has significant advantages in the field of load allocation for hydropower units. It effectively improves the stability and reliability of unit operation, and this method can be applied to practical load allocation processes. It is of great significance for the research on load allocation optimization of hydropower units.

A Dual Robust Strategy for Removing Outliers in Multi-Beam Sounding to Improve Seabed Terrain Quality Estimation.

During the process of seabed terrain exploration using a multi-beam echo system, it is inevitable to obtain a sounding set containing anomalous points. Conventional methods for eliminating outliers are unable to reduce the disruption caused by outliers over the whole dataset. Furthermore, incomplete consideration is given to the terrain complexity, error magnitude, and outlier distribution. In order to achieve both a high-precision terrain quality estimate and quick detection of depth anomalies, this study suggests a dual robust technique. Firstly, a robust polyhedral function is utilized to solve anomaly detection for large errors. Secondly, the robust kriging algorithm is used for refined outlier removal. Ultimately, the process of dual detection and anomaly removal is achieved. The experimental results demonstrate that DRS technology has the most favorable mean square error and error fluctuation range in the test set, with values of 0.8321 and [-2.0582, 1.9209], respectively, when compared to RPF, WT, GF, and WLS-SVM schemes. Furthermore, DRS is able to adjust to various terrain complexities, discrete distribution features, and cluster outlier detection, as shown by objective indicators and visual outcome maps, guaranteeing a high-quality seabed terrain estimate.

Numerical study on the flow characteristics and stability in the isolator of rotating detonation ramjet engine by different combustion modes and structure parameters

In this paper, numerical simulations are conducted to investigate the effects of the combustion modes and structure parameters of the combustion chamber of a rotating detonation ramjet engine(RDRE) generated within the isolator. The stability of the isolator in the combustion mode as a single or dual wave mode is evaluated. The influence of parameters such as the combustion chamber expansion angle and the outside diameter of combustion chamber is also taken into account. The results show that the propagation of the detonation wave in the combustion chamber in a dual-wave (DW) mode reduces the instability generated by the combustion chamber on the isolator. In the stability model, the fluctuation range of the single-wave (SW) mode accounts for 14.43 % of the total length of the isolator, while it is 4.67 % in the DW mode, which is reduced by 10.97 %. The DW mode is more capable of withstanding changes in the combustion state of the detonation chamber. In the SW mode, the back propagation pressure wave (BPPW) propagates to the inlet of the isolator, while the fluctuation range of the isolator in the DW mode only increases by 29.68 % and still maintains a stable working condition. Changing the length of the isolator and outer diameter of the combustion chamber, the DW mode can also accommodate changes in the combustion chamber structure without affecting the inlet flow status of the isolator.

The Temporal and Spatial Characteristics of Wind–Photovoltaic–Hydro Hybrid Power Output Based on a Cloud Model and Copula Function

In a high proportion of wind–photovoltaic–hydro hybrid power systems, fluctuation and dispersion make it difficult to accurately quantify the output characteristics. Therefore, in this study, a cloud model and copula correlation coefficient matrix were constructed for a hybrid power generation system based on the output data. Multiple backward cloud transformation based on the sampling-with-replacement method was proposed to calculate the improved entropy and hyperentropy to analyze the fluctuation range and dispersion degree quantitatively. A similarity index was proposed to evaluate the similarity between wind power, PV power, and hydropower. A suitable copula function was selected, and the Kendall and Spearman coefficients show the correlation relationships of the hybrid systems. The temporal and spatial characteristics of the hybrid systems were analyzed based on the two models. A typical example in Qinghai proved the effectiveness and applicability of the method. The results show that the correlation between photovoltaic power and hydropower is better and that, in summer, hydropower can be used to adjust the output of renewable energy.

Fabrication and characterization of Ni-TiO2 and Ni-V2O5 single-layer and double-layer coatings with the approach of improving the wear and corrosion properties

The main purpose of this study is to investigate the metallurgical behavior of Ni-TiO2 and Ni-V2O5 single-layer coatings and compare them with Ni-TiO2/Ni-V2O5 and Ni-V2O5/Ni-TiO2 double-layer coatings. The general attitude is the optimal choice of coatings in terms of wear and corrosion properties. The dimensions of TiO2 and V2O5 ceramic powders were 20 nm and 500 nm, respectively, and their morphology was also different. The presence of the submicron V2O5 particles was more than the TiO2 nanoparticles in the nickel matrix deposit. Also, with double layering the coatings (Ni-TiO2/Ni-V2O5 and Ni-V2O5/Ni-TiO2), the presence of ceramic particles in the upper layer had increased compared to the same single-layer coatings. Therefore, the increase in the hardness of the deposits was directly related to the percentage of ceramic powders in the coating. The surface morphology of the Ni-TiO2 layers was formed as a cauliflower shape while the Ni-V2O5 deposits had a smooth morphology. Increasing participation of TiO2 particles in the Ni-TiO2 layer had made the morphology rougher. Also, by applying the Ni-TiO2 layer under the Ni-V2O5 deposit, the surface morphology of the Ni-V2O5 layer became smooth, which can be due to the increase in the V2O5 content in this layer. The lowest amount of fluctuation appeared in the roughness profiles related to the Ni-V2O5 layers, and the large fluctuation range in the Ni-TiO2 layers was due to the smooth and cauliflower structure, respectively. The crystallite size in double-layer coatings was smaller than the single-layer coatings due to the higher nucleation and growth rate of nickel deposition in the nickel matrix upper layers. According to the presented results, the Ni-V2O5 and Ni-V2O5/Ni-TiO2 coatings were the most wear resistant coatings. Also, the Ni-V2O5/Ni-TiO2 and Ni-TiO2/Ni-V2O5 double-layer coatings were suitable candidates for corrosion resistance and to consider both properties, Ni-V2O5/Ni-TiO2 was very suitable. Hardness, surface morphology, roughness, preferred planar texture, and ceramics powder participation were important parameters in determining the wear and corrosion properties of coatings. Also, it seems that the effect of the double layering of nickel matrix deposits on the metallurgical properties was greater than the dimensions of the ceramic particles participating in the coating.

The evaluation of course teaching effect based on improved RBF neural network

As basic education is increasingly digitized, the need for better teaching and learning quality also rises. Teaching reform is crucial to achieve this, and incorporating the Levenberg-Marquardt (L-M) into the Radial Basis Function (RBF) can help establish a fair online teaching evaluation system. The experimental results showed that the convergence ability of the model was significantly improved compared with the traditional RBF neural network. The overall mean square error of the improved model was 10°. The actual value prediction accuracy of the improved model is higher than that of the Backpropagation (BP). When the actual value was at its peak, the accuracy reached 98 %, the overall fluctuation range of absolute error was low, the highest absolute error value reached 0.78, and the average absolute error was below 0.5. With targeted improvements, teachers and students could better understand and change their own learning situations, as reflected in empirical evaluations.

The Influence of Centerline Segregation on Impact Toughness in Welding Heat-Affected Zone of X70 Pipeline Steel

The influence of centerline segregation on the low-temperature impact toughness of the heat-affected zone (HAZ) of welded joints was studied by welding experiments on X70 steel plates rolled from continuous casting slabs with segregation grades of class 2 and class 3. The experimental results show that the impact toughness at HAZ from class 2 slab steel plate is more stable and has excellent low-temperature toughness than that of class 3 slab steel plate. The impact toughness of the HAZ of the class 3 slab steel plate is low to 100 J at −40 °C and has a severe fluctuation range (~150 J), and the delamination phenomenon is also observed in the fracture cross-section. The reason for this phenomenon is due to the enrichment of C and Mn elements in the centerline segregation zone. The formation of abnormal microstructure (martensite/bainite) in the segregation zone leads to stress concentration, which easily weakens the low-temperature toughness of the joint.