Mixed Conditions Research Articles

STATISTICAL ANALYSIS OF FRICTIONAL PROCESSESOF A SLIDING BEARING

This article addresses the issue of diagnosing friction nodes in sliding bearings, which are among the mostchallenging and complex topics in the tribological research. The article presents a methodology for diagnosingfriction nodes operating under variable loads based on the analysis of vibration acceleration signals from thebearing using statistical methods. In the study, statistical parameters were determined to assess the technicalcondition of sliding bearings operating with variable loads under dry and mixed friction conditions. Usingstatistical tools to interpret selected tribological parameters that occur in the friction process aims to ensure theproper operation of the tribological system under operating conditions. Analysis of the measurement resultspresented in the study using statistical tools will allow the development of a methodology to assess the correctoperation of sliding bearings.

Development of a protein production system using Ogataea minuta alcohol oxidase-deficient strain under reduced-methanol-consumption conditions.

Methylotrophic yeast is a useful host for producing heterologous proteins using the unique and strong alcohol oxidase 1 (AOX1) promoter, which is induced by methanol and repressed by various carbon sources. However, methanol is preferably avoided in industrial-scale fermentation given its toxicity, flammability, and explosiveness. To develop a protein production system under reduced methanol supply conditions, we attempted to characterize the AOX1 promoter induction activity by comparing between the de-repression and methanol induction conditions. This comparison is important because decreasing methanol consumption would enhance the industrial value of Ogataea minuta for heterologous protein production. For such a comparison, an alcohol oxidase-deficient (Δaox) strain was generated, with methanol only being used for AOX1 promoter induction. We also developed a culture process in a jar fermentor using the O. minuta Δaox strain under mixed feed conditions to achieve heterologous protein production comparable to that of the wild-type strain under low-methanol conditions.

Mean square consistency and improved rate of convergence of generalized subsampling estimator for non‐stationary time series

In this article, we show the mean square consistency for a generalized subsampling estimator based on the aggregation of the mean, median, and trimmed mean of some subsampling estimators for general non‐stationary time series. Consistency requires standard assumptions, including the existence of moments and ‐mixing conditions. We apply our results to the Fourier coefficients of the autocovariance function of periodically correlated time series. Furthermore, as in the i.i.d. case, we show that the generalized subsampling estimator satisfies Bernstein inequality and concentrates at an improved rate (under the condition of no or small bias) compared with the original estimator. Finally, we illustrate our results with some simulation data examples.

Evaluation of Wear Resistance in Tungsten-Doped Diamond-like Carbon Coatings (WC/C) on Coated and Uncoated Surfaces Under Starved Oil Lubrication with R452A Refrigerant

This article assesses the potential of using a diamond-like carbon coating doped with tungsten, a-C:H:W (WC/C), on the sliding pairs of refrigeration compressors. The ability of WC/C coating to provide low wear and a low coefficient of friction was experimentally verified in a specific refrigeration compressor operating environment (lubrication with oil diluted with refrigerant) and under extreme operating conditions (starved lubrication with a small amount of oil). Conditions of starved lubrication with a substance of reduced lubricity promote a temperature increase and high mechanical (friction) stresses on the surface of the sliding pairs. These situations can hinder the effective operation of WC/C coatings. Comparative wear tests were carried out for S235JR steel samples with and without WC/C coating. It was found that the samples with the WC/C coating had the lowest wear values and the lowest friction coefficients (approximately 0.06). A low coefficient of friction suggests that even a small amount of oil (one drop) is likely sufficient to achieve mixed lubrication conditions between the tested sliding surfaces and reduce material loss. The tested WC/C coating can protect sliding friction pairs in refrigeration compressors under extreme operating conditions caused by a lack of oil. Less friction reduces the need for energy to drive the refrigeration compressor. Additionally, the significance of this research is highlighted by the fact that the wear tests were conducted using R452A, a novel, eco-friendly refrigerant.

Cross-language facilitatory and inhibitory effects in the naming of Japanese words by Chinese-Japanese bilinguals

Abstract This study investigates the effects of orthographic and phonological overlaps between the first language (L1) and the second language (L2) during word naming by adult Chinese-Japanese bilinguals, in the light of the Orthographic Depth Hypothesis which posits that the processing of printed words depends on the extent of grapheme-phoneme correspondence in the language. We compared their naming performance of L2 Japanese words written in moraic hiragana which is not used in their L1 Chinese, morphosyllabic kanji utilized in L1, and a mixed condition. Results indicated a longer latency for naming L2 Japanese words with kun-reading which has no phonological overlap with L1, particularly when written in kanji, which has orthographic overlap with L1. Consistent with the Orthographic Depth Hypothesis, participants performed better for words in hiragana as a shallow orthography than for words in kanji as a deep orthography. Furthermore, this study examined the priming effect of L2 Japanese translation equivalents on L1 Chinese targets. We found more accurate and faster naming of L1 words semantically exposed by L2, suggesting that L2 semantic representation facilitates L1 translation equivalence.

Development of wear and pitting curves with vibration analysis for lubricating grease under contamination conditions

The application of grease under contaminated environmental conditions typically leads to its degradation and subsequent damage to lubricated surfaces. This study examines the effects of various concentrations of environmental particles and water content, both separately and in combination, on the variation of tribological characteristics of lithium-based grease during wear. Wear and pitting curves are established for grease contaminated with varying weight percentages of water and particles. The introduction of water into grease reduces wear by absorbing friction heat but increases pitting, while particles extend the running-in period and destabilize surface roughness. In mixed conditions, particles exert a greater influence on the tribological behavior than water. To improve pitting monitoring, vibration indicators FM4 and NA4 are modified by incorporating the cumulative effect of the friction coefficient over time, accounting for the progressive accumulation of wear and vibration energy. The modified FM4 indicator proves more effective in detecting pitting variations under contaminated conditions.

An implicit GNN solver for Poisson-like problems

This paper presents Ψ-GNN, a novel Graph Neural Network (GNN) approach for solving the ubiquitous Poisson PDE problems on general unstructured meshes with mixed boundary conditions. By leveraging the Implicit Layer Theory, Ψ-GNN models an “infinitely” deep network, thus avoiding the empirical tuning of the number of required Message Passing layers to attain the solution. Its original architecture explicitly takes into account the boundary conditions, a critical pre-requisite for physical applications, and is able to adapt to any initially provided solution. Ψ-GNN is trained using a physics-informed loss, and the training process is stable by design. Furthermore, the consistency of the approach is theoretically proven, and its flexibility and generalization efficiency are experimentally demonstrated: the same learned model can accurately handle unstructured meshes of various sizes, as well as different boundary conditions. To the best of our knowledge, Ψ-GNN is the first physics-informed GNN-based method that can handle various unstructured domains, boundary conditions and initial solutions while also providing convergence guarantees.

Facile Synthesis and Thermal Stability Enhancement of Sulfurized Polyacrylonitrile for Thermal Battery Cathodes

Although sulfide-polyacrylonitrile (SPAN) is considered a promising cathode material for various battery applications, their application in thermal batteries has not yet been explored. Herein we synthesized carbonized SPAN (c-SPAN) to enhance the thermal stability of SPAN and evaluated its application as a cathode for thermal batteries. The efficiency of c-SPAN materials was demonstrated by comprehensive structural analysis and thermal stability evaluation, including scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman, and thermogravimetric analysis (TGA). The c-SPAN exhibited significantly improved thermal stability compared to conventional PAN, which was attributed to the stable structure resulting from the chemical bonding of sulfur to the PAN-derived turbostratic carbon matrix. In addition, the bond dissociation energy of the C–S bond (272 kJ/mol) was higher than that of the S–S bond (251 kJ/mol), further contributing to the enhanced thermal stability. The thermal stability of c-SPAN was considerably affected by the mixing method and thermal treatments conditions, and maintained stability up to 500°C under optimal conditions. Additionally, a thermal battery incorporating c-SPAN was successfully operated, indicating that the c-SPAN material developed in this study is a viable candidate for thermal battery applications. These results suggest it is one of the promising cathode materials for various thermal battery applications.

Indications of a changing winter through the lens of lake mixing in Earth’s largest freshwater system

Abstract Global surface freshwater primarily resides in lakes, with the overwhelming majority found in Earth’s largest lakes, thus understanding potential climate change effects in these large lakes is critical. In dimictic lakes, climate change has extended the duration of summer thermal stratification and reduced the length of the ice season. These changes are relatively straightforward to evaluate in smaller, inland lakes. However in large lakes, such as the North American Great Lakes, temporally intermittent and spatially heterogeneous ice cover, and spatial thermal heterogeneity limit the utility of simple ice on-off or mixing classifications; therefore, assessing how climate change is impacting winter conditions in large lakes is challenging. Here, we use in-situ and satellite-derived surface water temperature observations from the North American Great Lakes to overcome these limitations and show that warming air temperatures are driving reductions in the number of winter days, collectively those with either ice cover or inverse thermal stratification, in favor of increases in isothermal conditions for the period 1995 to 2023. We find that on average the Great Lakes are experiencing a loss of 14 winter days per decade. Our results demonstrate how climate change has yielded disproportionate changes in the annual thermal cycle and mixing conditions of Earth’s largest freshwater system and signals the potential for fundamental ecosystem shifts due to a loss of winter.

Identifying the role of route choice behavior of motorcycle riders in microscopic simulation modeling under mixed traffic conditions

Microscopic simulation models are pivotal in transportation planning for their ability to intricately capture complex traffic patterns. This study specifically explores the role of dynamic route choice behavior within micro-simulation frameworks, emphasizing its application in the context of motorcycle-dominated traffic in Ninh Kiều District, Cần Thơ, Vietnam. By integrating discrete choice models for route selection with rigorous calibration and validation in AIMSUN, the study developed a comprehensive traffic simulation model for large-scale networks. Findings reveal that motorcycles dynamically adjust routes based on current traffic conditions rather than adhering strictly to shortest path strategies. However, the availability of roadside traffic information systems accessible to motorcycles in developing countries is limited, hindering optimal route choices. To address this gap and encourage the enhancement of route choice behavior, the study evaluates the impact of real-time traffic information provision using Macroscopic Fundamental Diagrams within the micro-simulation model. The results demonstrate significant improvements in network efficiency when informed route selection behaviors are facilitated, particularly with comprehensive coverage across all road types. Higher compliance rates notably improved network capacity by up to 84%. Overall, this study contributes methodologically by increasing model precision and practical insights into managing heterogeneous traffic environments, highlighting the transformative potential of traffic information systems and advocating for broader implementation in similar motorcycle-centric regions, which currently still rarely extend beyond toll roads. Future research should extend these methodologies to diverse urban contexts for broader validation and application.

Agreement and Reliability of Transpalpebral Tonometers with Goldmann Applanation Tonometer – A Systematic Review and Meta-Analysis

TopicThe systematic review and meta-analysis consolidates the extant body of evidence comparing reliability and agreement between Transpalpebral Tonometers (TT) and Goldmann Applanation Tonometer (GAT). Clinical RelevanceWith a global prevalence of 3.54 percent, glaucoma stands as the second leading cause of preventable blindness. Projections indicate a rise to 111 million cases by 2040. Existing literature presents inconsistent findings while comparing TT and GAT. The derivation of summary estimates assessing their agreement holds significance given TT’s multifaceted applicability in clinical, community, and home settings. MethodsSystematic review was conducted using PubMed, Cochrane Library, and Google Scholar from January 2000 to December 2022. Two reviewers independently evaluated, enumerated, and extracted studies and data based on eligibility criteria. The Quality Assessment for Diagnostic Accuracy Studies (QUADAS-2) checklist was used to assess study quality. The summary measures were pooled using the random effects model as mean difference (MD), and 95% LoA (Limits of Agreement). We assessed heterogeneity using the I2 statistic. The study protocol was registered with the International Prospective Register of Systematic Reviews (PROSPERO - CRD42022321693). ResultsA total of 26 methods comparison studies (3577 eyes) were included in the meta-analysis. The overall random-effects MD (TT – GAT), SD and 95% LoA for IOP were -0.70 ± 4.15 mmHg (-8.83 to 7.43 mmHg). In the subgroup analysis based on index test devices used, Easyton showed the lowest MD, SD (-0.29 ± 2.35 mmHg), and 95% LoA (-4.90 to 4.32 mmHg). In the univariate meta-regression model, we found that, on average, studies examining normal eyes reported a statistically significant lower mean difference of 2.67 mmHg (95% CI: 0.27 to 5.07 mmHg; P = 0.03) between TT and GAT, compared to studies that assessed eyes with mixed ocular condition. ConclusionIn the current meta-analysis, we found a small MD in the measured IOP between the two tonometers. However, given the high heterogeneity and a wider LoA, it is not advisable to use TT interchangeably with GAT.

Combustion performance of an evaporative flameholder under subsonic-supersonic mixing inflow

The combustion process in rocket-assisted subsonic ramjet engines represents a key advancement in integrated aerospace propulsion, particularly for embedded rocket-based systems. These engines offer the potential to improve combustion performance at altitudes of 25–35 km. However, the significant temperature and velocity differentials between the rocket jet and the subsonic ramjet flow restrict heat and mass transfer. Investigating the relationship between combustion performance and inlet parameters under subsonic-supersonic mixing conditions offers a promising approach to enhancing thrust performance. This study introduces subsonic and supersonic airflow mixing via a flat-plate shear layer in a rectangular channel, with an evaporative flameholder placed centrally to assess combustion. Results reveal that combustion efficiency decreases as the equivalence ratio exceeds 0.2, while the static temperature ratio has minimal impact on efficiency but strongly influences the maximum flame stabilization limit. As the temperature ratio increases from 1.30 to 1.80, the flame limit narrows from 1.656 to 0.237. Higher pressure ratios initially enhance combustion efficiency and flame coverage but eventually cause a decrease. The flame limit broadens from 0.900 to 1.626 as the pressure ratio increases from 1.12 to 1.50. While Mach number changes have little effect on efficiency, the flame limit exhibits an initial rise followed by a drop. Novel findings include an asymmetrical flame pattern and a “Z” shaped outlet temperature distribution, contributing to optimized combustion strategies for combined-cycle engines.

A Variable Horizon Model Predictive Control for Magnetorheological Semi-Active Suspension with Air Springs.

To improve the characteristics of traditional model predictive control (MPC) semi-active suspension that cannot achieve the optimal suspension control effect under different conditions, a variable horizon model predictive control (VHMPC) method is devised for magnetorheological semi-active suspension with air springs. Mathematical models are established for the magnetorheological dampers and air springs. Based on the improved hyperbolic tangent model, a forward model is established for the magnetorheological damper. The adaptive fuzzy neural network method is used to establish the inverse model of the magnetorheological damper. The relationship between different road excitation frequencies and the control effect of magnetorheological semi-active suspension with air springs is simulated, and the optimal prediction horizons under different conditions are obtained. The VHMPC method is designed to automatically switch the predictive horizon according to the road surface excitation frequency. The results demonstrate that under mixed conditions, compared with the traditional MPC, the VHMPC can improve the smoothness of the suspension by 2.614% and reduce the positive and negative peaks of the vertical vibration acceleration by 11.849% and 6.938%, respectively. Under variable speed road conditions, VHMPC improved the sprung mass acceleration, dynamic tire deformation, and suspension deflection by 7.191%, 7.936%, and 22.222%, respectively, compared to MPC.

Theoretical analysis of the piston ring-pack for predicting friction and power loss in an internal combustion engine

The piston ring is considered an essential element in the operation of the internal combustion engine to improve its efficiency and reduce its emissions. It is resistant to high temperature and high-pressure gases in the combustion chamber. A one-dimensional analysis method of lubrication between piston rings and cylinder liner in mixed lubrication conditions is developed in this article by using the GT-Suite simulation software. We applied the finite difference numerical method to solve the Reynolds equation to obtain the variation during an engine cycle of the following parameters; film thickness, frictional force, and power loss. The solution results presented can be used to improve the design of the piston ring pack in internal combustion engines and is available for industry usage.

Analysis of the three‐dimensional elasticity theory problem for a radially inhomogeneous cylinder

AbstractIn this paper an axisymmetric problem of elasticity theory for a radially inhomogeneous cylinder of small thickness is studied. It is assumed that homogeneous mixed boundary conditions are specified on lateral surfaces of the cylinder, and boundary conditions that leave the cylinder in equilibrium are specified on the ends of the cylinder. It is considered that elastic moduli are arbitrary continuous functions of a variable along the radius of the cylinder. The formulated boundary value problem is reduced to a spectral problem containing a small parameter characterizing the thinness of the cylinder walls. To determine its solution, the method of asymptotic integration is used, based on three iteration processes. All solutions of the equilibrium equation are constructed, satisfying the specified homogeneous boundary conditions on lateral surfaces. It is obtained that the solution of the problem consists of a penetrating solution and a solution of the nature of the boundary layer. An analysis of stress‐strain states corresponding to different types of solutions is carried out. Based on the constructed asymptotic solutions, a connection is found between the solutions obtained by the equation of elasticity theory and by the applied theory of shells. It is shown that the penetrating solution determines the internal stress‐strain state of a radially inhomogeneous cylinder. The stress state determined by the penetrating solution is equivalent to the principal vector of stress acting in a cross section perpendicular to the axis of the cylinder.The first terms of asymptotic expansions of the penetrating solution in a small parameter coincide with solutions in the applied theory of shells. New classes of solutions are defined as the character of a boundary layer, which are localized at the ends of the cylinder and decrease exponentially with distance from the ends. These solutions are absent in the applied theories of shells. The first terms of the asymptotic expansion of the solution, having the nature of a boundary layer, are equivalent to the Saint‐Venant edge effect in the theory of heterogeneous plates. Asymptotic formulas for displacement and stresses are constructed, allowing one to calculate the three‐dimensional stress‐strain state of a radially heterogeneous cylinder of small thickness with any predetermined accuracy. Based on the obtained asymptotic expansions, one can estimate the applicability areas of applied theories and construct a refined applied theory for radially heterogeneous cylindrical shells.

Displacement-potential analysis of ply-stresses in a partially guided non-uniform short-column of hybrid laminated composites

Reliable and accurate analysis of local stresses in structural problems of fiber-reinforced laminated composites involving nonuniform geometry is of utmost practical importance, especially when they are subjected to local loads and supports. In this research, a new study of ply stresses in a partially guided, nonuniform, short composite column of hybrid laminates, subjected to an eccentrically distributed loading is conducted using an efficient computational scheme. The analytical modeling of the present mixed-boundary-value problem of laminated structure is realized in terms of a single scalar function of space variables (called as displacement-potential function), which is defined by the displacement components of plane elasticity, and is governed by a single fourth-order partial-differential equation of equilibrium. In this modeling approach, the original three-dimensional symmetric laminated column is reduced to a plane-stress scalar-field problem of an equivalent imaginary lamina in an attempt to obtain the corresponding strain field (global laminate strain), which is then used to determine the stress fields of individual plies through the respective transformed reduced stiffness matrices. A finite-difference based computational scheme is developed to solve the representative nonuniform equivalent lamina in terms of the displacement-potential function, which is however well capable of dealing with different ply materials as well as fiber orientations, together with the associated mixed and changeable physical conditions along the boundaries of the column. A 28-ply balanced hybrid laminate composed of boron-epoxy and glass-epoxy plies with various fiber orientation is considered as the structural material for the present column. The stress fields obtained for individual plies as well as the overall laminate are analyzed in the perspective of a number of practical issues of structural design, which include material hybridization, eccentricity of loading and attachment of partial guides to the column. The design stresses of the nonuniform laminated column are identified to be affected significantly by the material and orientation of fibers as well as the laminate hybridization. An attempt is also made to verify the soundness and accuracy of the present computational scheme through the comparison of the present potential-function solutions with those obtained by the conventional computational method.

Determination of steady-state for continuous powder mixing: Analysis of mixture properties and signal processing

Continuous powder mixing offers many advantages over batch processes, but its industrial implementation requires control of transient phases due to startup or variations in operating conditions. Detecting the steady-state by observing the mixture properties, obtained through in-line analysis of the mixture composition, is challenging due to the significant fluctuations in these properties. However, there is no quantitative method for identifying the steady-state for continuous powder mixing. We therefore propose in this work a methodology for steady-state detection by comparing several methods of mixture property analysis and signal processing. We show that conventional methods of mixture property analysis cannot reliably and accurately detect steady-state. We conclude that the best methodology is to perform signal processing on the content of the key component in the mixture. To do this, the signal of the content of the key component is first smoothed by the Savitzky-Golay filter. Then, the standard deviation of the filtered signal is compared with a tuning parameter to detect the beginning of steady-state. This method could be used to determine the mixing conditions leading to the smallest startup time, hence avoiding costly waste.

Mechanism of Wheel-Rail Adhesion Recovery during Large Sliding processes under Water Lubrication condition

The challenge of low adhesion between the wheel and rail constrains the advancement of train braking technologies, resulting in sliding during braking, increased braking distances, and even operational safety incidents. Low adhesion arises from the contamination of the rail surface by a third body, such as water or oil, significantly reducing adhesion. However, experimental studies have found that wheel-rail adhesion coefficient under water lubrication conditions possesses a recovery capability: In scenarios characterized by low adhesion in water lubrication conditions, a secondary rise in adhesion occurs when substantial wheel-rail sliding is present. This paper focuses on numerically modeling the unique phenomenon of adhesion recovery during large-sliding processes under water lubrication conditions. Considering the notable differences in frictional heating during wheel sliding, as opposed to pure rolling conditions, we construct a wheel-rail contact model under mixed lubrication conditions that incorporates the solid-liquid coupled heat transfer effect. This model achieves stable solutions for the wheel-rail contact relationship and the temperature at the wheel-rail interface. The impacts of velocity, axle load, water temperature, and slide ratio on the adhesion recovery phenomenon are discussed, revealing the underlying mechanism of adhesion recovery during large sliding processes. Finally, brake adhesion tests under water lubrication conditions are conducted on a scaled test rig to validate the proposed theoretical model.

The Role of Mechanical Mixing and Biologically Active Additives in Enhancing Cutlet Quality

The research relevance is determined by the need to understand the effect of mechanical mixing and the use of biologically active additives on the quality of cutlet mass, which will optimize food technologies and create products with improved texture and nutritional value. This need stems from the fact that the quality and characteristics of culinary products are important criteria for consumers. The research aims to investigate the relationship between mechanical mixing parameters and the use of biologically active additives with structural and mechanical quality parameters of cutlet mass, to improve production processes and develop higher quality food products. Analytical methods, classification methods, functional methods, statistical methods, and synthesis methods were used to determine the quality of the cutlet mass. In the course of the study, a comprehensive analysis of the effect of various parameters of mechanical mixing and the use of various biologically active additives on the structural and mechanical characteristics of the cutlet mass was carried out. It was found that optimal mixing conditions and types of additional components can significantly improve the textural properties of the product. It was found that the use of certain biologically active additives helps to increase the resistance of the mass to mechanical stress and preserve its juiciness. These conclusions allow us to develop more effective strategies for the production of cutlet mass with improved quality and nutritional value. The practical significance of this study is to provide scientifically based recommendations for optimizing food production processes aimed at improving the quality and nutritional value of cutlet mass by studying the effect of mechanical mixing and biologically active additives on its structural and mechanical properties.

Environmental dependency of ectomycorrhizal fungi as soil organic matter oxidizers.

Forest soils play a pivotal role as global carbon (C) sinks, where the dynamics of soil organic matter (SOM) are significantly influenced by ectomycorrhizal (ECM) fungi. While correlations between ECM fungal community composition and soil C storage have been documented, the underlying mechanisms behind this remain unclear. Here, we conducted controlled experiments using pure cultures growing on naturally complex SOM extracts to test how ECM fungi regulate soil C and nitrogen (N) dynamics in response to varying inorganic N availability, in both monoculture and mixed culture conditions. ECM species dominant in N-poor soils exhibited superior SOM decay capabilities compared with those prevalent in N-rich soils. Inorganic N addition alleviated N limitation for ECM species but exacerbated their C limitation, reflected by reduced N compound decomposition and increased C compound decomposition. In mixed cultures without inorganic N supplementation, ECM species with greater SOM decomposition potential facilitated the persistence of less proficient SOM decomposers. Regardless of inorganic N availability, ECM species in mixed cultures demonstrated a preference for C over N, intensifying relatively labile C compound decomposition. This study highlights the complex interactions between ECM species, their nutritional requirements, the nutritional environment of their habitat, and their role in modifying SOM.