Speed Conditions Research Articles

Numerical and experimental study on the mechanism of added resistance in stepped moonpool under different waves

To study the additional resistance effect of the moonpool during the navigation of the drilling vessel, this paper explores the variation of the drilling vessel resistance under different waves based on a model test and numerical simulation. The difference between the model test and the numerical simulation results is compared, and the mechanism of the added resistance of the moonpool under different waves is revealed. The results show that the technology of numerical simulation is able to accurately simulate the navigation resistance of the drilling vessel in waves. The numerical simulation results closely correspond to the experiment results, and the error range can be controlled within 10%. In the components of the total resistance of the hull, pressure resistance plays a dominant role when the drilling vessel sails in waves. The pressure resistance accounts for about 60%–70% of the total resistance, while the friction resistance accounts for about 30%–40% of the total resistance. At low speed, the average resistance reduction rate of the dissipative equipment is 4.4%; under the condition of medium speed, it is 7.5%; at high speed, it is 9.6%; and the resistance reduction efficiency of the dissipative equipment increases with the increase in speed. The dissipative equipment partially suppresses the eddy's action stage and prevents eddy shedding from entering and directly hitting the back wall, thereby reducing the moonpool's additional pressure resistance. The research results can provide a reference for energy savings and emission reductions in drilling vessels.

Sensitivity-Aware Density Estimation in Multiple Dimensions.

We formulate an optimization problem to estimate probability densities in the context of multidimensional problems that are sampled with uneven probability. It considers detector sensitivity as an heterogeneous density and takes advantage of the computational speed and flexible boundary conditions offered by splines on a grid. We choose to regularize the Hessian of the spline via the nuclear norm to promote sparsity. As a result, the method is spatially adaptive and stable against the choice of the regularization parameter, which plays the role of the bandwidth. We test our computational pipeline on standard densities and provide software. We also present a new approach to PET rebinning as an application of our framework.

Bigels as Novel Drug Delivery Systems: A Systematic Review on Efficiency and Influential Factors.

Bigles are novel formulation merging two phase of hydrogel and organogel revealing dual properties to release active agents based on their lipophilic or hydrophilic nature. A systematic search was conducted in PubMed, Scopus, and ISI Web of Science to find eligible studies evaluating the efficiency of bigels in drug release. 20 articles were included in the analysis based on the defined criteria. The results indicated that several different natural materials were used for bigel making. Span (52.38%) and Sunflower oil (23.80%) were the most solvents used for organogel formation. Also, gelatin, agar, gums, and other types of biopolymer were used as hydroglators. Most research (33.33%) focused on the release of metronidazole from bigel structure. Also, the range of drug release rates was 1.59 - 100% and in 42.85% of studies was >90%. The nature, content, and properties of both organogel and hydrogel and some process variables such as temperature, mixing speed and storage conditions were highlighted as the main influential factors on bigel formation and its bioactivity. Bigels are an innovative structure that provides desired physicochemical and rheological properties for industrial applications. Excellent biocompatibility and in vitro / ex vivo results have been documented for developed bigels. In this regard, an optimal preparation method is very important to show superior therapeutic effects.

Development of a method for evaluating fabric surface contamination by particulate matter using fluorescent particles

Functional clothing products are being developed to prevent the attachment of particulate matter (PM). However, currently, PM-blocking performance of such products cannot be quantitatively evaluated. This study developed a method for measuring fabric surface contamination by PM by contaminating textile fabrics with PM and using an image processing technique. Silicate particles exhibiting fluorescence characteristics with a suitable size distribution were selected as PM simulants. The fabric surface contamination was calculated by contaminating textile fabrics under wind speed and PM concentration conditions similar to actual atmospheric environment. The number of pixels was obtained in the black and white binary images converted from the images of the textile fabrics captured under an ultraviolet (UV) light source. Experiments were performed using finished nylon fabric with PM-blocking performance and raw nylon fabric without PM-blocking performance. Comparison of the fabric surface contamination shows that it is possible to evaluate the PM-blocking performance of fabrics.

Grapevine, peach, and plum response to simulated florpyrauxifen-benzyl drift

Abstract Off-target movement of rice herbicides is a concern in California, where sensitive crops are often grown nearby. Florpyrauxifen-benzyl and triclopyr are auxin-mimics commonly used in rice systems. To steward florpyrauxifen-benzyl around the time of its initial registration in the state, research was conducted to compare the onset of foliar symptoms from simulated florpyrauxifen-benzyl and triclopyr drift onto grapevine, peach, and plum. The rates were 1/200X, 1/100X, 1/33X, and 1/10X of the 29.4 g ai ha–1 florpyrauxifen-benzyl and 1/200X, 1/100X, and 1/33X of the 420.3 g ae ha–1 triclopyr rice use rates. Herbicides were applied on one side of one- to two-year-old peach and plum trees and one side of established grapevines in 2020 and 2021. The general symptoms for florpyrauxifen-benzyl and triclopyr were similar and included chlorosis, leaf curling, leaf distortion, leaf malformation, leaf crinkling, necrosis, and twisting on leaves. The symptoms from herbicides were observed on both sides of the grapevine canopy, whereas florpyrauxifen-benzyl symptoms on peach and plum were mostly observed on the treated side of the tree. Florpyrauxifen-benzyl and triclopyr symptoms were observed three days-after-treatment (DAT) for grapevines and seven DAT for peach and plum. In all crops, most symptoms persisted through 42 DAT. Some grape clusters showed deformation and dropping of berries. All treated crops gradually recovered during the season regardless of application rates. Because symptoms were relatively minor in peach and plum, this research suggested that application precautions that reduce off-site drift are likely to minimize the occurrence of significant injury. However, grapevines were more sensitive and showed injury symptoms up to 71% at 14 DAT with a 1/10X florpyrauxifen-benzyl simulated drift rate. Therefore, extra precautions such as using drift-management agents and proper wind speed conditions at the time of florpyrauxifen-benzyl applications may be necessary if there are nearby vineyards.

CFD simulation and experimental investigation of a Magnus wind turbine with an improved blade shape

With the advancement of technology and growing concern for environmental issues, the demand for energy derived from renewable sources is expected to increase. It is well established that traditional bladed wind turbines exhibit inefficiency in low wind speed conditions. To address this, Magnus wind turbines, featuring cylindrical blades, have been developed specifically for regions with predominantly low-speed winds. However, these turbines present a significant drawback, as they require electric drives to rotate the blades. This study aims to conduct a three-dimensional numerical and experimental investigation of the aerodynamics around a wind turbine with a geometrically complex blade design. The scientific contribution of this work lies in the introduction of a deflector to the cylindrical blades, intended to eliminate the need for an electric drive to initiate blade rotation. A laboratory prototype of a wind turbine with the proposed blade configuration was constructed, and numerical simulations were performed using Ansys Fluent, based on the Reynolds-averaged Navier—Stokes (RANS) equations. The results demonstrate that the turbine's power coefficient (Cp) is approximately 20 % higher than that of traditional Magnus wind turbines. These findings underscore the enhanced efficiency provided by the addition of a deflector to the cylindrical blades.

Performance assessment of direct injection stoichiometric and lean burn compressed natural gas engine over port fuel gasoline and compressed natural gas engine

ABSTRACT A direct injection (DI) CNG engine was developed and evaluated under stoichiometric and lean burn conditions, emphasising high compression ratios (CRs). A comparative analysis of PFI gasoline and PFI CNG engines was conducted to provide comprehensive insights. Results showed that the DI CNG engine exhibited a shorter combustion duration, indicating higher combustion speed, and enhanced combustion stability, particularly at low load and speed conditions, with a reduced coefficient of variation of indicated mean effective pressure (COVIMEP) below 1%. The DI CNG engine demonstrated a relative increase in net indicated thermal efficiency by 4–5% compared to the PFI CNG engine. Furthermore, CNG engines operating at a high compression ratio of 16 could run at high loads without encountering knocking issues. Lean burn operation, combined with high compression ratios, improved thermal efficiency while minimising emissions; however, challenges such as combustion instability and increased emissions under lean burn conditions were observed.

Uncertainty-driven dynamic ensemble framework for rotating machinery fault diagnosis under time-varying working conditions

Multi-scale ensemble learning combines different scales of feature resolution, thereby improving fault diagnostic accuracy. However, the effectiveness of different information scales in characterizing fault features under time-varying speed conditions varies with speed. It is difficult for existing ensemble strategies to ensure the effectiveness of feature information when ensemble multi-scale feature information is involved. Accordingly, we propose an uncertainty-driven dynamic ensemble Bayesian convolutional neural network (DEBCNN) framework. The uncertainty of the results of different scale models was used to dynamically determine their weights in the ensemble framework, which reduced the influence of irrelevant features on the diagnostic results. By employing the proposed dynamic ensemble strategy, the ensemble framework can utilize fault feature information corresponding to different rotational speeds in the final diagnostic results. Experiments on motor and bearing datasets illustrate the superiority of this strategy over other techniques. This study provides useful insights for further research in the field of fault diagnosis of rotating machinery at time-varying speeds.

An innovative 4D printing approach for fabrication of anisotropic collagen scaffolds

Collagen anisotropy is known to provide the essential topographical cues to guide tissue-specific cell function. Recent work has shown that extrusion-based printing using collagenous inks yield 3D scaffolds with high geometric precision and print fidelity. However, these scaffolds lack collagen anisotropy. In this study, extrusion-based 3D printing was combined with a magnetic alignment approach in an innovative 4D printing scheme to generate 3D collagen scaffolds with high degree of collagen anisotropy. Specifically, the 4D printing process parameters-collagen (Col):xanthan gum (XG) ratio (Col:XG; 1:1, 4:1, 9:1 v/v), streptavidin-coated magnetic particle concentration (SMP; 0, 0.2, 0.4 mg ml-1), and print flow speed (2, 3 mm s-1)-were modulated and the effects of these parameters on rheological properties, print fidelity, and collagen alignment were assessed. Further, the effects of collagen anisotropy on human mesenchymal stem cell (hMSC) morphology, orientation, metabolic activity, and ligamentous differentiation were investigated. Results showed that increasing the XG composition (Col:XG 1:1) enhanced ink viscosity and yielded scaffolds with good print fidelity but poor collagen alignment. On the other hand, use of inks with lower XG composition (Col:XG 4:1 and 9:1) together with 0.4 mg ml-1SMP concentration yielded scaffolds with high degree of collagen alignment albeit with suboptimal print fidelity. Modulating the print flow speed conditions (2 mm s-1) with 4:1 Col:XG inks and 0.4 mg ml-1SMP resulted in improved print fidelity of the collagen scaffolds while retaining high level of collagen anisotropy. Cell studies revealed hMSCs orient uniformly on aligned collagen scaffolds. More importantly, collagen anisotropy was found to trigger tendon or ligament-like differentiation of hMSCs. Together, these results suggest that 4D printing is a viable strategy to generate anisotropic collagen scaffolds with significant potential for use in tendon and ligament tissue engineering applications.

Effect of electrical current on sliding friction and wear mechanisms in a-C and ta-C amorphous Carbon coatings

This study investigated the sliding wear behaviour of amorphous carbon (a-C) and tetrahedral amorphous carbon (ta-C) coatings, two forms of diamond-like carbon (DLC) coatings, against SAE 52100 steel using a modified ball-on-disk tribometer with applied electrical currents ranging from 100 mA to 1800 mA. It focused on the variations in sliding friction and wear characteristics of these coatings as electrical currents increased under constant load and speed conditions. The a-C coatings exhibited lower coefficient of friction (COF) values and reduced volumetric wear losses up to 1500 mA, while ta-C coatings studied displayed higher wear, similar to uncoated M2 steel, at 300 mA with degradation occurring at low currents, resulting in failure due to severe oxidational wear. The a-C coatings showed no significant electrical damage at these currents. Raman spectroscopy revealed structural changes on the wear tracks of sp2-rich a-C coatings, specifically the formation of graphene layers. In comparison, the wear tracks of sp3-rich ta-C coatings did not display such transformation under the conditions studied. The graphene coverage on the surfaces of the a-C coatings increased with the increase in the current as revealed by the Raman intensity maps of 2D peaks and this increase was accompanied by a higher defect density in the graphene. The low COF of graphene-covered a-C surfaces was consistent with the proposed mechanisms of moisture adsorption. However, at currents exceeding 900 mA, surface temperatures of a-C coatings exceeded 100 °C, impairing graphene's ability to maintain low friction, resulting in an increased COF.

Thermo-mechanical coupling characteristics of the shearer’s guiding shoe during the friction

The reliability and longevity of the guiding shoe are crucial for the proper functioning of coal mining machines. The heavy wear of the sliding surface under thermal stress coupling is the primary factor influencing the service life of the guiding shoe. To reveal the heat flow distribution patterns and the thermo-stress coupling mechanisms of the guiding surface, a thermo-mechanical coupling model of the guiding shoe and the pin row is established. The transient thermodynamic behavior of the guiding shoe under different load and speed conditions is studied using the coupled temp-displacement analysis method in Abaqus. The results indicate that the overall temperature of the guiding shoe friction surface experiences a rapid increase during the initial running-in phase, followed by a progressively slower temperature increase over time. Temperature and stress concentration regions on the friction surface primarily localize at the corners of the shoe groove, and the distribution of temperature and stress shows a strong coupling. Furthermore, elevated traction speed and mechanical load exacerbate the thermo-elastic instability of the guiding shoe, consequently augmenting thermal stress on the friction surface. The increase in support load results in significant thermal shock on the lower area of the left side of the guiding shoe. The research provides a reference for exploring the fatigue failure and wear mechanisms of the guiding shoe while considering thermal effects.

System response time and optimal path

Abstract In this work we study, in general terms, the optimal path for an out-of-equilibrium process from a geometric perspective constructed from a probability density function belonging to the exponential family (PDFE). With this objective we have constructed the speed of entropy production for a system out of equilibrium. This speed of entropy production is not determined with respect to the clock time t but rather with respect to a dimensionless time ξ (t) associated with a characteristic response time of each system λ (t). In this context, we demonstrate that the constant entropy production speed condition leads to the system moving on a geodesic of the manifold constructed from the probability density function. In the last part of this work we apply our general results to study the Ornstein–Uhlenbeck process (OU), which is a well-known stochastic process that strictly speaking describes the velocity of a Brownian particle under the influence of friction. As the system evolves we find that dimensionless time ξ (t) passes slower than clock time t.

Investigation of Engine Exhaust Heat Recovery Systems Utilizing Thermal Battery Technology

Over 50% of an engine’s energy dissipates via the exhaust and cooling systems, leading to considerable energy loss. Effectively harnessing the waste heat generated by the engine is a critical avenue for enhancing energy efficiency. Traditional exhaust heat recovery systems are limited to real-time recovery of exhaust heat primarily for engine warm-up and fail to fully optimize exhaust heat utilization. This paper introduces a novel exhaust heat recovery system leveraging thermal battery technology, which utilizes phase change materials for both heat storage and reutilization. This innovation significantly minimizes the engine’s cold start duration and provides necessary heating for the cabin during start-up. Dynamic models and thermal management system models were constructed. Parameter optimization and calculations for essential components were conducted, and the fidelity of the simulation model was confirmed through experiments conducted under idle warm-up conditions. Four distinct operational modes for engine warm-up are proposed, and strategies for transitioning between these heating modes are established. A simulation analysis was performed across four varying operational scenarios: WLTC, NEDC, 40 km/h, and 80 km/h. The results indicated that the thermal battery-based exhaust heat recovery system notably reduces warm-up time and fuel consumption. In comparison to the cold start mode, the constant speed condition at 40 km/h showcased the most significant reduction in warm-up time, achieving an impressive 22.52% saving; the highest cumulative fuel consumption reduction was observed at a constant speed of 80 km/h, totaling 24.7%. This study offers theoretical foundations for further exploration of thermal management systems in new energy vehicles that incorporate heat storage and reutilization strategies utilizing thermal batteries.

ПОВТОРЯЕМОСТЬ АДВЕКТИВНО-РАДИАЦИОННЫХ ТУМАНОВ НАД АПШЕРОНСКИМ ПОЛУОСТРОВОМ (АЗЕРБАЙДЖАН)

The article examines the physical and meteorological characteristics of advective-radiation fogs formed on the Apsheron Peninsula and nearby islands, including the dependence of atmospheric elements that influence the formation of fogs on the meteorological visibility range, monthly and long-term fog trends. For this purpose, the initial data of aviation meteorological stations in the water area for 1999...2022 were used. The absence of a large morphometric unit on the Apsheron Peninsula and the archipelago, surroundings by the sea, and air masses affecting the area throughout the year determine its synoptic conditions. With the help of physical-meteorological and mathematical-statistical analyses, it has been established that the bulk of advective-radiation fogs formed in the Apsheron waters are repeated in march...april. With this type of fog, it has been established that the range of meteorological visibility varies depending on wind speed and sky conditions. During the period of advective-radiation fogs, south-eastern winds are most often observed in the water area. Analyzes show that an increase in average monthly and annual air temperatures on the peninsula has recently affected the frequency of advective-radiation fogs. Studying the spatiotemporal distributions of fogs can create conditions for the effective organization of aviation work.

Performance degradation modeling of civil aviation engines based on component characteristic map optimization

In order to provide a theoretical basis for the degradation of the air path performance of civil aviation engines at the unit level, the CFM56-3 engine was used as the research object. First, on the basis of using the characteristic map scaling method to obtain the component characteristic equation, the selection process of the scaling reference point of the fan general characteristic map was optimized, and a surface fitting method of the characteristic map was proposed to construct an engine component-level benchmark performance model that meets specific speed conditions under steady-state conditions. Then, by introducing the fault factor to generate the fault coefficient matrix, the deviation of the engine monitoring parameters as the component efficiency decreases was calculated, and compared with the fingerprint map data of the GE training manual, it was verified that the engine steady-state performance model that integrates the fan characteristic map scaling reference point optimization and the characteristic map surface fitting method has good accuracy and use in the analysis of air path performance degradation.

Enhancing SRM Performance through Multi-Platform Optimization and FPGA-Based Real-Time Simulation

This paper proposes a multi-platform algorithm methodology in order to define firing angles of torque sharing functions (TSFs) for the indirect torque control of switched reluctance motors (SRM) through a hardware-in-the-loop (HIL) system. This proposal is used to achieve optimal levels of torque ripple and losses with accuracy and reliability, while taking advantage of real-time simulation. The analysis is performed assuming steady-state conditions of speed and torque reference for levels below the base speed, aiming to obtain firing angles ensuring optimal tracking performance. A novel methodology is proposed by using a grid search algorithm that handles the communication between Python, Code Composer, and the Typhoon HIL device. For that, an experimental data FPGA-based model with 500~ns of simulation time step is used to ensure highly accurate dynamic responses of current and electromagnetic torque. Moreover, controller-HIL (C-HIL) is used to have a safe and high fidelity testing environment, allowing rapid testing before transitioning to an experimental test bench. The simulation results are experimentally validated, demonstrating that the proposed strategy is effective and ensures optimal performance, taking into account peripheral systems of A/D, signal conditioning, PWM, and sensor emulation.

Analysis of the Nonlinear Complex Response of Cracked Blades at Variable Rotational Speeds

The operation of an aero-engine involves various non-stationary processes of acceleration and deceleration, with rotational speed varying in response to changing working conditions to meet different power requirements. To investigate the nonlinear dynamic behaviour of cracked blades under variable rotational speed conditions, this study constructed a rotating blade model with edge-penetrating cracks and proposes a component modal synthesis method that accounts for time-varying rotational speed. The nonlinear response behaviours of cracked blades were examined under three distinct operating conditions: spinless, steady speed, and non-constant speed. The findings indicated a competitive relationship between the effects of rotational speed fluctuations and unbalanced excitation on crack nonlinearity. Variations in rotational speed dominated when rotational speed perturbation was minimal; conversely, aerodynamic forces dominated when the effects of rotational speed were pronounced. An increase in rotational speed perturbation enhanced the super-harmonic nonlinearity induced by cracks, elevated the nonlinear damage index (NDI), and accentuated the crack breathing effect. As the perturbation coefficient increased, the super-harmonic nonlinearity of the crack intensified, resulting in a more complex vibration form and phase diagram.

Effects of Structure Parameters on Static Performance of Gas Foil Bearings Based on a New Fully Coupled Elastic–Aerodynamic Model

Abstract: Accurately predicting the performance of gas foil bearings (GFBs) is important. This paper presents a new fully coupled elastic–aerodynamic model for analyzing the static performance of gas foil journal bearings (GFJBs). The gas compressible lubrication model was solved in MATLAB to obtain the gas pressure. The foil structure deformation was solved in COMSOL by considering the Coulomb friction and allowing the contact surfaces to be separated from each other. Under given load and rotational speed conditions, the calculated minimum gas film thickness and attitude angle match well with the literature data, validating the accuracy of the developed model. Based on the model developed, a comprehensive and systematic analysis of the effects of the structural parameters on the static performance was performed. The results showed that as the bump height, top foil thickness, and bump foil thickness increased, the load capacity could be improved to different degrees. The bump foil thickness had the greatest effect on the load capacity. These results provide theoretical guidance for the structural design and practical applications of GFJBs.

The Problem of Power Variations in Wind Turbines Operating under Variable Wind Speeds over Time and the Need for Wind Energy Storage Systems

One of the most important and efficient sources of green electricity is catching air currents through wind turbine technology. Wind power plants are located in areas where the energy potential of the wind is high but it varies. The time variation of the wind generates fluctuations in the power produced by the wind farms that is injected into the grid. This elevates, depending on the intensity, problems of network stability and the need for balancing energy, thus raising both technical and cost issues. The present paper analyzes the behavior of a wind turbine (WT) over time in varying wind speed conditions, highlighting that without automation algorithms, a WT is far from the operation at the maximum power point (MPP). However, even when it is brought to operate at MPP, there are still significant variations in the power injected into the network. These power variations can be compensated if the wind system has energy storage facilities for the captured wind. All of these assumptions are analyzed using improved mathematical models and processed in simulations, with experimental data used as input from a wind turbine with an installed power of 2.5 [MW] in operation on the Romanian Black Sea coastal area. Consequently, the paper demonstrates that during an operation in the optimal area, from an energy perspective, the wind turbine’s maximum power point requires a storage system for the captured wind energy.

Effect of Ultrasound on Microstructure and Properties of Aluminum–Copper Friction Stir Lap Welding

In this paper, the influence mechanism of ultrasound on plastic flow and microstructure features of the aluminum–copper friction stir lap welding (Al/Cu-FSLW) process is systematically investigated by adjusting the welding speed and improving the shear rheology in the plastic stirring zone. Through adjusting the ultrasonic vibration and welding speed, the directional control of mechanical properties is realized. It is found that increasing the welding speed properly is beneficial to enhance the mechanical shear between the tool and the workpiece, thus forming more staggered layered structures at the copper side and improving the tensile strength of the weld. The acoustic softening enhances the viscoplastic fluid mixing and strengthens the mechanical interlock of the Al/Cu lap interface. As the welding speeds increase or ultrasonic vibration is applied, the thickness of Al/Cu intermetallic compound (IMC) decreases, and the tensile strength and elongation of the Al/Cu joints are enhanced. Compared with adjusting the welding speed, the ultrasonic vibration can further refine the copper particles which are stirred into the plastic zone, and the thinning effect of ultrasound on IMC layers is better than that of increasing welding speed. At the welding speed of 60 mm/min, the IMC layer thickness is reduced by 42% under ultrasonic effect. In three welding speed conditions, the UV reduced the absolute value of the effective heat of formation (EHF) for Al2Cu and Al4Cu9 and suppressed the formation of AlCu phase. Meanwhile, only when the welding speed is increased from 60 mm/min to 100 mm/min can the formation of AlCu be suppressed. Under the ultrasonic optimization, the stable improvement of welding efficiency is ensured.