Analysis Of Variance Method Research Articles

Reliability analysis of plate parts with multiple interacting hole-edge cracks using complex variable function

In this paper, a successive conformal mapping technique is used to propose an analytical method for solving the stress intensity factor (SIF) of asymmetrical hole-edge cracks on the basis of Muskhelishvili's complex variable function analysis method. Based on this analytical solution, the superposition method is used to get the SIF under the interaction of multiple cracks. Subsequently, according to the plastic collapse criterion, the residual strength under the interaction of two collinear asymmetric elliptical hole-edge cracks with different sizes on the side rail of a dumper's frame is analyzed through the method established. The failure probability of the plate part is obtained by the Kriging meta-model. This study provides a theoretical guide for the operation and maintenance plan of plate parts with multiple cracks.

A high-precision online compensation method for random errors of optical gyroscope

The traditional Allan variance cannot reflect the time-varying characteristics of random error signals, and the dynamic Allan variance cannot simultaneously guarantee both the signal dynamic tracking performance and confidence of variance estimation due to adopting the sliding window with fixed window length to intercept and segment random error signals. To address these issues, a dynamic Allan variance analysis method with adaptive window length is proposed. Based on the idea of piecewise stability of time-varying random error signals, a sliding window is introduced to intercept and segment the signal to be analyzed along the time axis, and the Allan variance analysis results of all signal segments are synthesized to track and describe the time-varying characteristics of the signal. Then according to the changes in the statistical characteristics of the random error signal, an adaptive factor is constructed to adaptively adjust the length of the sliding window, thereby guaranteeing both the signal dynamic tracking performance and confidence of variance estimation at the same time. On this basis, this method is applied to the online compensation of optical gyroscope random errors, and then a high-precision online compensation method for random errors of optical gyroscope is proposed. The experimental results show that the proposed method can achieve high-precision online compensation for the time-varying random error signals of optical gyroscope measured in complex environment such as uncertainty and noise interference.

A comprehensive evaluation of the effects of bamboo nodes on the mechanical properties of bamboo culms

Architectural pavilions made of round bamboo are undergoing rapid development due to their appealing appearance and low carbon footprint, but their structural analysis is challenging due to the existence of bamboo nodes. Generally, bamboo nodes provide positive effects on the mechanical behavior of bamboo culms in terms of evolution. However, the loading conditions of bamboo culms used in buildings greatly differ from the natural conditions. Some studies have been conducted on this issue but come to different conclusions. In this regard, this work conducts a comprehensive study on the effects of bamboo nodes on the mechanical properties of bamboo culms. A total of 168 specimens divided into four types were tested, including compressive, tensile and shear tests parallel to the grain and radial compressive tests. The load–displacement curves and failure modes were analyzed. The analysis of variance method was used to evaluate the effects of bamboo nodes on the mechanical properties. A comprehensive discussion based on fiber morphology is presented to explain the effects of nodes under different load conditions. Additionally, the fiber distribution in the diaphragm was observed, and the compressive strength of the diaphragm was tested. It was found that the bamboo node had significant effects on the tensile strength and radial compressive modulus. Compared to the bamboo culm without nodes, the tensile strength of bamboo culm with nodes decreased by 47%, while the node could improve the pipe stiffness by 123%. In compressive and shear tests parallel to the grain, the bamboo node showed slight effects on the strength. The differences in both strengths were all within 9% in value. Based on the geometric model, the relationship between the fiber morphology and the mechanical properties was built. In short, the bamboo node showed less improvement in compressive and shear tests parallel to the grain but should be carefully considered in tensile conditions due to its weakening effect.

Heavy grazing causes plant cluster fragmentation of sparse grasses.

Cleistogenes songorica, as a clustered grass, is the main grassland flora of the Stipa breviflora desert grassland. Some studies have shown that the constructive species of S. breviflora (sparse cluster type) is prone to cluster fragmentation; however, research on C. songorica is relatively rare. Then will the C. songorica plant population (dense cluster type) also have cluster fragmentation under the influence of intense grazing? To answer this question, we used variance analysis and geo-statistical methods. The spatial distribution of C. songorica in S. breviflora desert steppe in Inner Mongolia was measured under four grazing intensities (no grazing, CK, 0 sheep·ha-1·half year-1; light grazing, LG, 0.93 sheep·ha-1·half year-1; moderate grazing, MG, 1.82 sheep·ha-1·half year-1; and heavy grazing, HG, 2.71 sheep·ha-1·half year-1) and four scales (10 cm × 10 cm, 20 cm × 20 cm, 25 cm × 25 cm, 50 cm × 50 cm). We then analyzed C. songorica whether fragmentation was present. The results showed that increased grazing intensity is associated with increased density and decreased height, coverage, and standing crop of C. songorica. The spatial distribution of C. songorica was affected by structural factors, and spatial heterogeneity decreased with increased spatial scale. With increased grazing intensity and spatial scale, the patch area of C. songorica gradually increased and tended toward band distribution. In summary, increased grazing intensity and spatial scale led to weakened heterogeneity of C. songorica spatial distribution and increased consistency.

The Association of Nocturnal Seizures and Interictal Cardiac/Central Autonomic Function in Frontal Lobe Epilepsy: Heart Rate Variability and Central Autonomic Network Analysis.

Patients with epilepsy frequently experience autonomic dysfunction, closely related to sudden unexplained death in epilepsy (SUDEP). SUDEP occurs most often at night or during sleep, and frequent nocturnal seizures are an established risk factor. This study investigated the influence of nocturnal seizures on autonomic dysfunction in epilepsy. This retrospective study enrolled frontal lobe epilepsy (FLE) patients who performed 24-hour EEG monitoring. All participants were divided into nocturnal FLE (NFLE, > 90% of seizures occurring during sleep) or diurnal FLE (DFLE) groups. EEG and ECG signals were simultaneously obtained during waking and sleep stages. EEG current density source and connectivity analysis of the autonomic network were performed. ECG was analyzed across time and frequency domains heart rate variability (HRV) analysis method was used. The obtained parameters were compared between the NFLE and DFLE groups. Fifteen NFLE and 16 DFLE patients were enrolled with no significant difference in age, sex, disease duration, seizure frequency, or the number of anti-seizure medications between the two groups. During sleep, a decrease in HRV parameters and an increase of the beta-1 (13-22 Hz) current source density power in the bilateral paracentral lobule (BA4,5,6), precuneus (BA7), and cingulate (BA31) were observed in the NFLE group compared to DFLE group. The NFLE group also showed hyperconnectivity in the central autonomic (12 edges distributed over 10 nodes), sympathetic (2 edges distributed over 3 nodes), and parasympathetic (4 edges distributed over 6 nodes) beta-1 frequency band networks during sleep. During wakefulness, central and cardiac autonomic variables were not significantly different between the NFLE and DFLE groups. Interictal cardiac and central autonomic dysfunction occurred simultaneously and can be attributed to the brain-heart autonomic axis. Our findings suggest that nocturnal seizures may contribute to interictal autonomic dysfunction during sleep in people with epilepsy.

Redefined decision variable analysis method for large-scale optimization and its application to feature selection

Redefined decision variable analysis method for large-scale optimization and its application to feature selection

Performance, Selection indices for six cotton genotypes to yield and some Components

According to the randomized complete block design, a field experiment was conducted at the Agricultural Research Station in the Daquq Research Station located 40 km south of Kirkuk at the longitude 28 - 44 ° east and latitude 8 - 35 ° north as a factorial experiment with three factors, six genotypes, three doses of potassium fertilizer, and two spacing between lines, the data were analyzed as a factorial experiment using the analysis of variance method, and the trait averages were compared using Duncan's multi-range test at a probability threshold of 5% for all of the traits evaluated. Montana genotype shows the superiority of No. of fruiting branches with an average of (8.15), Coker 310 genotypes No. of balls per plant with an average of (17.81), Montana genotype boll weight with an average of (4.85), and Coker 310 genotypes of Seed cotton yield per plant show an average of (87.26). While for fertilizer, it exceeded (200) Kg h-1, No. of fruiting branches with an average of (8.29), No. of balls per plant of (17.66), boll weight with an average reached (4.86), and Seed cotton yield per plant, with an average of (84.36). As for the distances between the lines, the distance exceeds 60 cm, in Seed cotton yield per plant with an average of 83.99. As for the best selection index, it was (the number of boll per plant and seed cotton yield per plant which amounted to (124.9922), and the expected genetic improvement was I1234, which included (number of fruiting branches, number of boll per plant, boll weight, and seed cotton yield per plant), which amounted to (8.7753), and the highest relative efficiency of the I2 index, which included (number of bolls per plant) as it reached 3109.95).

Analysis of Multicultural Behavior of Senior High School Students

Adequately student multicultural behavior was one of the indicators of successful schooling. Presumably, the students who lived in rural or small city areas had less opportunity to interact with culturally diverse peers. This study aimed to examine their multicultural behavior in the school environment. Using a survey procedure quantitative approach, involved 100 respondents selected randomly, consisting of 34 in 10th grade, 32 in 11th grade, and 34 in 12th graders in Batumarta, a small city in South Sumatera Province, Indonesia. Data of students’ multicultural behavior were obtained by administering a questionnaire, a self-report four scales of Likert. It consisted of 36 items assessing their expressing multicultural behavior in five dimensions. For data analysis, after managing the ordinal data and converting them into interval data, we used a line chart to display the students’ multicultural behaviors according to their frequencies in each dimension and compared mean scores of multicultural behaviors based on gender and grade levels by using the analysis of variance method. In conclusion, we found most students have a moderate frequency in expressing multicultural behavior, male and female students had dissimilar multicultural behavior, there were no multicultural behavior differences among the three grade levels, and the predominantly ethnic students were not different from their peers. Finally, we recommended the school develop a multicultural behavior program.

Relationships of the gall midge, Asphondylia miki Wachtl (Diptera, Cecidomyiidae), with the host plant, alfalfa (Medicago sativa) and ectoparasites of its larvae and pupae (Hymenoptera, Eulophidae) in the forest-steppe of the middle volga region

The studies were carried out in crops of alfalfa ( Medicago sativa ssp. × varia ) in 2018-2022 in the forest-steppe of Samara Province. Asphondylia miki galls were taken into account in alfalfa crops from the beginning of their formation to the end of the growing season on sites from 0.1 to 1 m2 in 10-fold repetition. Statistical processing of the obtained data was carried out by methods of variance analysis. At spring sowing of alfalfa, as well as in its perennial crops, gall midge A. miki develops in two, and during summer sowing in the rst year of the culture’s life in one generation per year, pupae overwinter in galls, the imago of the wintering generation occurs in April. The greatest damage to alfalfa by the larvae of A. miki (40-68% of generative shoots) and the number of its galls (500-830 copies/m2) were observed in the rst year of the culture’s life when it was sown in summer, with the coincidence of the greatest ight of imago with the budding of the culture, which led to signi cant losses in the yield of alfalfa seeds (13-81%). In summer alfalfa crops of the rst year of development without the use of chemical plant protection agents, parasitic hymenopterans contribute to the death of larvae and pupae of A. miki in on average 60% of its galls. Among them, a gregarious ectoparasite Sigmophora brevicornis (Eulophidae) mainly preying on A. miki larvae accounted for about 77% of the individuals of the identi ed parasites. In the S. brevicornis population, males and females had similar body coloration and belonged to three phenotypes: the lightest brownish yellow, yellowish brown, and dark coloration, which accounted for 53, 28 and 19% of parasite individuals, respectively.

Experimental study on influence mechanism of fiber orientation angle in AFRP cutting

The experimental study on aramid fiber-reinforced composites (AFRP) was carried out. The milling experiments of AFRP were carried out from different fiber orientations. The changes in surface quality, fiber section, and chip shape in mPIC1195147illing under different fiber orientations were studied, and the action law of the blade and tooth was analyzed from the micro perspective. The response surface are used to analyze the cutting force. The mathematical model is established to predict the minimum cutting force. The variance analysis method is used to analyze the influencing factors and their weights of cutting force. The research shows that the cutting force is the smallest when the fiber orientation angle is 0° or 90°, the milling surface quality is good, and the chips are primarily powdery. The cutting force is the largest when the fiber orientation angle is 45° and the milling surface quality is poor. The chips are mainly flocculent. At this angle, the cutting force is affected by three factors, and the interaction has the most significant proportion. When the fiber orientation angle is 30° or 60°, the cutting force, the fiber cross-section, and the surface quality are between the former two, and most of the chips are mixed chips (powdery and flocculent). The evolution and distribution law of burr is obtained. During AFRP milling, the milling surface is always sheared on one side and accompanied by extrusion. The fibers are sheared and broken, the surface burrs are few, the side is stretched, the fibers are stretched and broken, and the surface burrs are many. The action rule of the cutting tool on transverse and longitudinal fibers is summarized.

Investigating Whether the Ensemble Average of Multi-Global-Climate-Models Can Necessarily Better Project Seasonal Drought Conditions in China

Global drought patterns are substantially impacted by climate change, with far-reaching implications for socioeconomic and ecological systems. Existing global climate models (GCMs) are unable to accurately project precipitation and drought characteristics, particularly in countries or regions with complex topography and significant seasonal variability, such as China. Consequently, the purpose of this study is to assess the efficacy of GCMs, and their multi-model ensemble mean, as well as to investigate the seasonal drought characteristics in China using precipitation data from CMIP6 under various “possible future” scenarios. This study selected five GCMs with historical (1961–2014) and future (2015–2100) periods, namely CNRM-CM6-1, GFDL-ESM4, MPI-ESM1-2-HR, MPI-ESM1-2-LR, and NorESM2-MM, as well as their ensemble mean ENS-CGMMN. Based on the China Daily Precipitation Analysis Product (CPAP) as the reference precipitation, the performance of these models is evaluated using the DISO index and the quantile mapping (QM) method for calibration, as well as seasonal-scale drought using the standardized precipitation index (SPI) and spatiotemporal variability analysis methods. In comparison to other climate models and the ensemble mean, the calibrated MPI-ESM1-2-HR model can more precisely describe the actual precipitation conditions at the seasonal scale. Under four scenarios, China’s climate will shift from arid to moist in the future period (2015–2100) (SSP126, SSP245, SSP370, and SSP585). Autumn and summer will see a considerable increase in China’s moisture levels. During the autumn, winter, and spring, the moisture will generally increase in the northern subregions of China, including the Qinghai-Tibet Plateau (QTP), Xinjiang (XJ), Northwest (NW), Northeast (NE), and North China (NC). Dryness will decrease in southern subregions, such as the Southwest (SW) and South China (SC). In contrast to these three seasons, summer in XJ exhibits a distinct trend of aridity, especially in the SSP245 scenario, whereas the NE, NC, and SC exhibit a distinct trend of moisture. To be more specific, the aridity changes in subregions during various seasons under different future climate scenarios vary significantly. This study’s findings can provide significant support for future research on climate change and drought, which can help improve the accuracy of future climate projections and serve as a reference for drought risk management and policy formulation.

Relationship between vertical facial morphology and dental arch measurements in class II malocclusion: a retrospective study.

To evaluate the relationship between dental arch measurements and the vertical facial pattern determined in skeletal Class II untreated patients. Lateral cephalograms and plaster models were obtained from 124 untreated female adults (average age: 17.6 ± 3.8 years). Class I (CI), Class II Division 1 (CII/1) and Class II Division 2 (CII/2) malocclusions were divided into three subgroups according to their vertical morphology as hypodivergent, normodivergent and hyperdivergent. The multivariate variance analysis (MANOVA) method was used in the comparison of measurement values according to vertical and sagittal morphology. The relationship between both A point-Nasion-B point (ANB) and Frankfurt-mandibular plane (FMA) angles and dental arch measurements was examined by Pearson correlation analysis. The significance level was received as p < 0.05. While vertical morphology has a statistically significant effect on mandibular arch length, sagittal morphology affects maxillary arch depth. The parameters influenced by both morphologies are maxillary and mandibular arch length, as well as maxillary intermolar width. The mandibular arch length was significantly shorter in hyperdivergent-CII-2 malocclusion (50.5 ± 7.4 mm). Larger values were obtained in both mandibular arch length and maxillary arch depth measurements in CII-1 malocclusion compared to CII-2 malocclusion. The maxillary intermolar width was significantly shorter in hypodivergent-CII-1 malocclusion (46.8 ± 3.4 mm), while it was higher in hypodivergent-CI malocclusion (51.1 ± 3.4 mm). The maxillary arch length was the lowest in hyperdivergent-CI malocclusion (63.1 ± 13.3 mm) and the highest in hypodivergent-CI malocclusion (72.8 ± 7.6 mm). Additionally, a positive but weak correlation was found between ANB and FMA angles. Dental arch measurements have been found to be affected by both vertical facial morphology and skeletal sagittal relationship. A positive correlation was found between ANB and FMA angles.

Sample size planning for multiple contrast tests.

Sample size calculations for two (independent) samples are well established and applied in (pre-)clinical research. When planning several samples, which is common in, for example, preclinical studies, sample size planning tools based on analysis of variance methods are available. Since the underlying effect sizes of these methods are often hard to interpret and to provide for the sample size planning, we employ multiple contrast test procedures for sample size computations in both parametric (under normality assumption) and nonparametric designs using Steel-type tests. Since the exact distributions of the test statistics are unknown under the alternative and variance heterogeneity, we use approximate solutions. Furthermore, since no closed formula for the sample size is available, we use numerical approximations for their computation. Extensive simulation studies are finally conducted to assess the quality of the approximations. It turns out that the methods are accurate in the sense that the multiple contrast test procedures reach the target power to detect the alternative of interest with the sample size computed. The developed procedures are a valuable tool to plan (pre-)clinical trials with several samples and are easily accessible in publicly availablesoftware.

Direct Dispensation of Prenatal Supplements With Iron and Anemia Among Pregnant People

Postpartum transfusion is the most common indicator of severe maternal morbidity in the US. Higher rates of anemia are associated with a higher blood transfusion rate. To determine if providing, rather than recommending, supplements with iron at prenatal visits in a medically underserved community is associated with improved hematologic indices and reduced blood transfusion. In this quality improvement study, patients who delivered between May 13 and December 13, 2020, and thus were provided a prenatal supplement with iron throughout pregnancy were compared with those who delivered between January 1 and August 1, 2019, before supplements were dispensed. The study was conducted at Parkland Health, a safety net hospital in Dallas, Texas, with a 95% Medicaid-funded or self-pay population and included all patients who delivered at our institution during the study period with available hematologic data. In the earlier cohort, all patients were recommended to obtain and take iron supplements. In the later cohort, prenatal supplements with iron were dispensed via clinic pharmacy to all patients during prenatal visits. Maternal hematocrit levels (28-32 weeks, delivery admission, and discharge), rates of anemia (hematocrit <30%), and postpartum transfusion for acute blood loss anemia were compared using χ2 and analysis of variance methods with P < .05 considered significant. The analysis took place in July of 2022. Overall, 13 910 patients (98%) met inclusion criteria (mean age [SD], 27.9 [6.5] and 27.6 [6.5] years, mean [SD] body mass index at first visit, 29.2 [6.6] and 29.3 [6.6]). Mosty of the patients in both cohorts were of Hispanic ethnicity (76%). Providing iron-containing prenatal supplements was associated with higher average hematocrit levels at all time points including a mean difference of 1.27% (95% CI, 1.13%-1.42%) on admission for delivery, when compared with those who were not directly dispensed iron. Among patients prior to providing supplements, 18% had anemia on admission compared with 11% with iron-containing supplements dispensed (risk ratio [RR], 0.61; 95% CI, 0.56-0.66). Postpartum transfusion for acute blood loss anemia was reduced by one-third in patients after program implementation from 10 per 1000 to 6.6 per 1000 (RR, 0.62; 95% CI, 0.43-0.91). In this quality improvement study, providing supplements with iron to patients at prenatal visits was associated with improved hematocrit levels, rates of anemia, and reduced transfusions unrelated to obstetric catastrophes among a predominantly Medicaid population.

Quantification of polycyclic aromatic hydrocarbons in roasted Tan lamb using fluorescence hyperspectral imaging technology

Polycyclic aromatic hydrocarbons (PAHs) are one of the main harmful substances produced during the roasting of lamb. In this study, fluorescence hyperspectral imaging (FHSI) at different excitation wavelengths was used for the rapid determination of total PAHs (T-PAHs) content in roasted Tan lamb. Heterogeneous two-dimensional correlation spectroscopy (H2D-COS) was performed to resolve the fluorescence hyperspectral peaks. Competitive adaptive reweighed sampling (CARS), uninformative variable elimination (UVE), variable combination population analysis (VCPA), iterative retained information variable (IRIV) and interval variable iterative spatial shrinkage analysis (iVISSA) methods were employed to extract effective wavelengths to reduce data dimensionality. Partial least squares regression (PLSR), least squares support vector machine (LS-SVM) and convolutional neural network (CNN) algorithms were used to develop the T-PAHs content prediction model. For the FHSI at 357 nm excitation wavelength, the Smoothing-CARS-PLSR quantitative prediction model worked the best, with RC2 and RP2 reaching 0.9011 and 0.9169, and RMSEC and RMSEP reaching 0.0179 mg/kg and 0.0181 mg/kg, respectively. For the FHSI at 452 nm excitation wavelength, Smoothing-VCPA-CNN showed the best results, with RC2 and RP2 of 0.9199 and 0.9189, and RMSEC and RMSEP reaching 0.0175 mg/kg and 0.0171 mg/kg, respectively. This study provided a reference for the quantitative detection of PAHs.

Sccomp: Robust differential composition and variability analysis for single-cell data

Cellular omics such as single-cell genomics, proteomics, and microbiomics allow the characterization of tissue and microbial community composition, which can be compared between conditions to identify biological drivers. This strategy has been critical to revealing markers of disease progression, such as cancer and pathogen infection. A dedicated statistical method for differential variability analysis is lacking for cellular omics data, and existing methods for differential composition analysis do not model some compositional data properties, suggesting there is room to improve model performance. Here, we introduce sccomp, a method for differential composition and variability analyses that jointly models data count distribution, compositionality, group-specific variability, and proportion mean-variability association, being aware of outliers. sccomp provides a comprehensive analysis framework that offers realistic data simulation and cross-study knowledge transfer. Here, we demonstrate that mean-variability association is ubiquitous across technologies, highlighting the inadequacy of the very popular Dirichlet-multinomial distribution. We show that sccomp accurately fits experimental data, significantly improving performance over state-of-the-art algorithms. Using sccomp, we identified differential constraints and composition in the microenvironment of primary breast cancer.

Experimental study of heat affected zone for CO2 and fiber laser machining of SS 316L material

Stainless steel is a widely used engineering material. This material is difficult to machine by conventional methods because of its high melting point. The main aim of present experimental study is to investigate of the process parameters on HAZ (heat affected zone) for CO2 and fiber laser machining of SS 316L material. The cut qualities are analyzed by measuring the HAZ by altering the process variables like cutting speed, gas pressure and laser power. The experimentation is performed on Bystronic laser cutting machine. Design of experiment (DOE) technique using response surface methodology is used. Mathematical calculations are carried out using analysis of variance method. The main conclusion that is drawn from this study is change in laser power affects the HAZ. It is also observed that cutting speed is the most significant parameter as compared to gas pressure and laser power.

Exploration of the molecular mechanism of insulin resistance in adipose tissue of patients with type 2 diabetes mellitus through a bioinformatic analysis.

We aimed to determine the cis-expression Quantitative Trait Loci (cis-eQTL) and trans-eQTL of differentially expressed genes (DEGs) in insulin resistance (IR) related pathways. The expression profile data for insulin sensitivity (IS) and IR in the adipose tissue of patients with type 2 diabetes mellitus (T2DM) were acquired from the Gene Expression Omnibus databases. Then, the Gene set enrichment analysis (GSEA) and Gene set variation analysis (GSVA) methods were performed to identify the significant enrichment of potential Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways between IS and IR groups, and the Wilcoxon rank sum test was carried out to identify the DEGs related to KEGG pathways. Finally, the cis-eQTLs and trans-eQTLs that can affect the expression of DEGs were screened from the eQTLGen database. The GSEA and GSVA analysis indicated that the mTOR signaling pathway, insulin signaling pathway and T2DM had a strong correlation with the pathological process of T2DM. Furthermore, six genes (ACACA, GYS2, PCK1, PRKAR1A, SLC2A4, and VEGFA) were found to be significantly differentially expressed in IR-related pathways. Finally, we have identified a total of 1073 cis-eQTLs and 24 trans-eQTLs. We screened out six genes that were significantly differentially expressed in IR-related pathways, including ACACA, GYS2, PCK1, PRKAR1A, SLC2A4, and VEGFA. Moreover, we discovered that these six genes were affected by 1073 cis-eQTLs and 24 trans-eQTLs.

Taguchi optimization of tribological properties and corrosion behavior of self-lubricating Al–Mg–Si/MoS2 composite processed by powder metallurgy

Self-lubricating aluminum matrix composites (AMCs) can be used to reduce the wear and coefficient of friction (COF) in automotive engine components in which the use of liquid lubricants is not desirable. High temperatures accelerate the oxidation and thermal degradation of a liquid lubricant. In this study, we used powder metallurgy (PM) technique to prepare self-lubricant (MoS2)-based Al–Mg–Si AMCs, designated as Al–Mg–Si–xMoS2 (x in wt.%; x = 1.5, 2.0, 30, 3.5, and 4.0). The dry sliding wear properties were assessed using a pin-on-disk tribometer at various applied loads (20–50 N) and sliding distances (1000–3000 m), based on the Taguchi model (L9). Furthermore, electrochemical corrosion tests such as open circuit potential (OCP) and potentiodynamic polarization (PDP) were performed in a 3.5 wt% NaCl medium. The morphology of the Al–Mg–Si–xMoS2 composites was observed through scanning electron microscopy and energy dispersive spectroscopy to clarify the particle distribution and chemical composition. The results indicated that the addition of MoS2 to Al–Mg–Si decreased the wear and COF and increased the corrosion resistance, compared with those of the pristine Al–Mg–Si matrix alloy under same operating conditions. As the sliding distance increased to 250 m, the COF fluctuated, but it stabilized as the distance approached 3000 m. The effects of the load and reinforcement concentration were more significant than those of the sliding distance and track diameter, as predicted by the Taguchi model and analysis of variance methods.

Parametric optimization and clad characterization of composite coating prepared on Ti-6Al-4V alloy using TiB[formula omitted]-Ni-Yb[formula omitted]O[formula omitted] precursor powders

In this work, TIG cladding on Ti-6Al-4V substrate is executed by Taguchi L9 orthogonal array with three input process parameters viz.current, scanning speed and wt% of rare earth (RE). The fluctuating output responses (clad layer thickness (CLT), microhardness (MH) and wear rate (WR)) are optimized by using the desirability function analysis technique. The developed linear regression models are found highly accurate with 97.57%, 88.60% and 96.76% adjusted R2 values for CLT, MH and WR respectively. The multi-objective function of output responses is converted into a combined objective known as composite desirability (CD). The main effect on CD gives current as the most influencing factor followed by wt% of RE and scanning speed. The analysis of variance method is also applied to check the significance of input parameters on individual responses. Pair-wise input parameter variation of individual output responses are studied through contour plots. Sub-surface morphology of coating prepared at optimum condition shows dendritic, needle-like, coralline and short-columnar type microstructure with hard phases like TiB and NiTi. The aforesaid coating has a coefficient of friction of 0.24. The mechanism for wear is adhesion with ploughing and shearing of materials.