Effect Of Gradient Research Articles

Wheel tread temperature assessment and its impact on rolling contact fatigue under long-term braking conditions

To analyze the temperature rise of the wheel tread under braking conditions and its impact on the rolling contact fatigue (RCF) of the wheels, this paper proposes a numerical analysis method based on thermodynamics, material mechanics, and wheel-rail contact mechanics. This method has features of simplicity and fast computing speed. The study shows that the temperature rise of the wheel tread is mainly affected by the thermal friction between the brake pad and the wheel tread. The effects of track gradient, braking speed, and ambient temperature on wheel tread temperature rise are 16 °C/‰, 9.4 °C/km h⁻¹ , and 10 °C/°C, respectively. Therefore, reducing the gradient of the track, locomotive braking speed, and braking duration can help reduce the wheel tread temperature, thereby slowing the development of RCF of the wheels. The study shows that the value of RCF considering the temperature rise of the wheel tread is about 1.55 times that without considering the temperature rise, while the value of wear damage is reduced by 23 %. Therefore, when analyzing wheel damage, the comprehensive effects of RCF, wear, plastic flow, and temperature are recommended to be considered from different angles to provide a basis for reducing wheel damage.

Duration of exposure to compound daytime-nighttime high temperatures and changes in population exposure in China under global warming

Global warming has led to the enhancement of diurnal (daytime-nighttime) compound heat waves, which can severely affect the population’s physical health and productive life; this is particularly the case for vulnerable populations that are more susceptible to psychological and physiological harm with the future normalization of heatwave scenarios. In this study, we attributed the changes in population exposure under diurnal compound high temperatures (HTs) and extremely high temperatures (EHTs) to the influence of climatic (exposure duration) and population factors and their combined influence to determine the relationship between exposure duration and the changes in exposure of vulnerable populations. Diurnal compound HT and EHT covered a land area of 4,016,800 and 1,984,200 km2, respectively. The heat-exposed area spread step-like in all directions, centering on the 24-h high-exposure area with a strong gradient effect. The area of prolonged exposure shifted from the Yellow-Huai-Huai Plain across the geographical boundary between the south and the north to the middle and lower reaches of the Yangtze River Plain. Meanwhile, the average maximum value of vulnerable population exposure reached 186,800 and 93,100 person-h, with high values in Zhengzhou, Chongqing, Wuhan, Chengdu, Beijing, and other cities. Changes in vulnerable population exposure were dominated first by demographic factors and then by climatic factors, with the dominance of climatic factors evident in areas of prolonged exposure. Under prolonged exposure to daytime-nighttime compound EHT, changes in the exposure of child and older populations were dominated by climatic factors with a contribution rate of 87.16% and 87.43%, respectively. Therefore, suitable cooling measures should be proposed for vulnerable populations under prolonged exposure, focusing more on the physical and mental health of children and older adults exposed to compound EHT.

THz Radiation from Subwavelength Volumes on Water Surfaces and in Air: Effects of Mass Density Gradients and External Magnetic Fields

THz Radiation from Subwavelength Volumes on Water Surfaces and in Air: Effects of Mass Density Gradients and External Magnetic Fields

Elastomeric Ionic Hydrogel-Based Flexible Moisture-Electric Generator for Next-Generation Wearable Electronics.

Rapid consumption of traditional energy resources creates utmost research interest in developing self-sufficient electrical devices to progress next-generation electronics to a level up. To address the global energy crisis, moisture-electric generators (MEGs) are proving to be an emerging technology in this field, capable of powering wearable electronics by harvesting energy from abundantly available ambient moisture without any requirement for external/additional energy. Recent advances in MEGs generally utilize an inorganic, metal, or petroleum-based polymeric material as an active material, which may produce sufficient current but lacks the flexibility and stretchability required for wearable electronics. Herein, we prepared an elastomer-based ionic hydrogel as an active material, and an MEG was fabricated by placing the ionic hydrogel on a PET sheet with two copper tapes on both sides of the hydrogel. The preparation of the hydrogel was thoroughly optimized and characterized in terms of spectroscopic analysis, swelling, water retention, and mechanical and rheological studies. The highly stretchable (350%) fabricated MEG is capable of producing a short-circuit current (JSC) of 16.1 μA/cm2, an open-circuit voltage (VOC) of 0.24 V, and a power density of 3.86 μW/cm2. The synergistic effect of the ion concentration gradient and the redox reaction on electrodes can be considered MEG's working principle. Apart from the current generation, this device is also used as a self-powered electronic sensor to monitor different physical activities by measuring breathing patterns. This prepared device is also capable of sensing the proximity of a hand. Therefore, our low-cost, easily fabricable, sustainable MEG device can be a potential aspirant for next-generation self-powered wearable electronics in healthcare applications.

Dorsal arachnoid web of the thoracic spine associated with an arachnoid cyst and a presyrinx state as an unexplained cause of thoracic myelopathy: illustrative case.

Dorsal thoracic arachnoid web is a rare diagnosis and is not commonly seen in neurosurgical practice. Patients can present with symptoms and signs of thoracic myelopathy in the setting of an arachnoid cyst and a presyrinx state. A 57-year-old male with a 10-year history of worsening bilateral leg weakness and chronic back pain re-presented to the neurosurgery clinic after being seen by neurology and orthopedic spine surgery. Initial imaging was concerning for myelomalacia and syringomyelia, and repeat delayed computed tomography myelography findings were consistent with an evolving thoracic arachnoid web, now demonstrating spinal cord compression secondary to arachnoid cyst formation and consistent with the signs of thoracic myelopathy. Intraoperative ultrasound displayed the arachnoid web as the cause of the evolving arachnoid cyst, edematous spinal cord, and a presyrinx-like state. The patient underwent surgical decompression, which restored cerebrospinal fluid (CSF) dynamics, resulting in clinical improvement. Dorsal thoracic arachnoid web is a dynamic condition that can occur in the setting of an arachnoid cyst. There appears to be a relationship between dorsal thoracic arachnoid web formation and the presence of an arachnoid cyst resulting from a ball-valve mechanism leading to the creation of a pressure gradient effect that alters CSF fluid dynamics. https://thejns.org/doi/10.3171/CASE24313.

A Moore-Gibson-Thompson heat conduction problem with second gradient

In this work, we study, from both analytical and numerical points of view, a heat conduction model which is based on the Moore-Gibson-Thompson equation. The second gradient effects are also included. First, the existence of a unique solution is proved by using the theory of linear semigroups, and the exponential energy decay is also shown when the constitutive tensors are homogeneous. The analyticity of the semigroup is also discussed in the isotropic case, and its spatial behavior is studied. The spatial exponential decay is also proved. Then, we provide the numerical analysis of a fully discrete approximation obtained by using the finite element method and an implicit Euler scheme. A discrete stability property is shown, and some a priori error estimates are derived, from which the linear convergence is concluded under suitable regularity conditions. Finally, some one-dimensional numerical simulations are presented to demonstrate the accuracy of the approximations and the behavior of the discrete energy.

Steady state regimes in lid driven cavity flows of magnetic fluids in the presence of an external magnetic field

In this work, we study the flow of magnetic fluids in a square top lid driven cavity in the presence of an applied magnetic field. The magnetic field is generated by a steady electric current flowing through a wire placed underneath the cavity. The magnetization of the magnetic fluid is described by an evolution equation that combines magnetization relaxation, advection and interaction with the flow via the vorticity. The governing equations are solved via a vorticity-streamfunction formulation implemented in a finite difference scheme. The main governing physical parameters of the examined cavity flow are the Reynolds number, ranging from 50 to 500, the magnetic pressure coefficient, which measures the relative importance between magnetic and inertial forces, ranging from 0 to 1000, and Péclet number which is O(1) and measures the ratio between the magnetization relaxation time and the flow time scale. We have examined the different mechanisms which cause changes in the local fluid magnetization, i.e., flow vorticity and advection. In particular, we examine how vorticity of the flow intensifies deviations of the magnetization of the fluid with respect to the local equilibrium of magnetization. In addition, we identify a complex topological structure of the flow inside the cavity characterized by the magnetic effects that dominate the generation of secondary structures of vorticity induced by the effect of field gradient, orientation and a non-uniformity in the fluid magnetization inside the cavity.

The effect of vertical temperature gradient on the equivalent depth in thin atmospheric layers

AbstractThe equivalent depth of an atmospheric layer is of importance in determining the phase speed of gravity waves and characterizing wave phenomena. The value of the equivalent depth can be obtained from the eigenvalues of the vertical structure equation (the vertical part of the primitive equations) where the mean temperature profile is a coefficient. Both numerical solutions of the vertical structure equation and analytical considerations are employed to calculate the equivalent depth, , as a function of the atmospheric layer's thickness, . Our solutions for layers of thickness 100 2000 m show that for baroclinic modes, can be over two orders of magnitudes smaller than . Analytic expressions are derived for in layers of uniform temperature and numerical solutions are derived for layers in which the temperature changes linearly with height. A comparison between the two cases shows that a slight temperature gradient (of say 0.65 K across a 100 m layer) decreases by a factor of 3 (but can reach a factor of 10 for larger gradients) compared with its value in a layer of uniform temperature, while a change of 10 K in the layer's uniform temperature hardly changes . The baroclinic mode exists in all combinations of boundary conditions top and bottom while the barotropic mode only exists when the vertical velocity vanishes at both boundaries of the layer.

Effects of position layout and length gradient of two side ducts of on methane/air explosion in a tube

ABSTRACT In order to examine how two side ducts affect the dynamic behavior of a gas explosion in a tube, two side ducts were added to a tube containing a mixture of 9.5% methane and air. An experiment was conducted to release the explosion pressure and study how the position and length gradient of the side ducts influence the explosion’s overpressure and the speed at which the flame spreads. Based on the data, it was found that the most effective pressure release occurred at a length of 0.2 m for the front side duct and 0.1 m for the end side duct. Additionally, the greatest explosive overpressure recorded was 2.54 kPa. A double driving effect was created between the two side ducts when they were put in the front and middle and the middle and end locations. This increased the flame propagated speed. The greatest acceleration effect on the flame front occurred at 0.2 m of side duct length. When the two side ducts were placed at the front and end of the tube, the length gradient did not have any impact on flame propagation. Instead, it was predominantly the length of the front side duct that controlled flame propagation. The pressure relief effect was more pronounced when the two side ducts had a downward gradient; however, it was affected by the length of the end side duct. A relationship equation was established between the lengths of the two side ducts (d 1 and d 2), positioned at the front and end locations, and the maximum flame velocity (Vmax). The analysis results of the impact of different positioning layouts and length gradients of two side ducts on flame propagation and pressure release within the tube were instrumental in ensuring the safety of personnel, equipment, and environment during energy utilization processes.

Effect of Membrane Thickness and Operating Conditions on PEMFC Limiting Current Analysis

Hydrogen powered proton exchange membrane fuel cells (PEMFC) have great potentials to replace the traditional internal combustion engines due to its inherent advantages of zero greenhouse gas emissions, better fuel efficiency, quick startup, silent operation, less required maintenance, etc. In a PEMFC, oxygen transport is a critical performance limiting factor because of the sluggish oxygen reduction reaction kinetics. Limiting current method is a well-established in-situ diagnostic tool to measure the oxygen transport resistance in a PEMFC. To obtain accurate oxygen transport resistances, a few key assumptions need to be made including: (1) the effect of temperature gradient in the diffusion media is negligible, (2) no convective flow in the porous media, (3) oxygen is diluted in a gas mixture of nitrogen and water vapor, (4) the total oxygen transport resistance combines gas diffusion layer, microporous layer, and catalyst layer, (5) the effect of membrane thickness has negligible effect, and (6) the anode side does not affect the measurement results due to fast hydrogen oxidation reaction. In this study, we perform a systematic study of the effect of membrane thickness and operating conditions on obtaining robust and reliable limiting current measurement. Standard Nafion membranes of three different thicknesses (25, 50, and 85 µm) are tested with Toray 060 and Freudenberg H23C8 diffusion media. In addition, we further study the interaction between membrane thickness and asymmetric pressure and relative humidity and their effects on limiting current results. Our results show that membrane thickness and relative humidity are critical factors in obtaining reliable oxygen transport resistance due to their effect on overall water balance in the cell. Lastly, the experimental data are compared with the simulation results to establish fundamental understanding. Detailed experimental and analytical results will be presented at the conference.

More is not always better: revealing the impact of cumulative risk on health-promoting behaviors among miners and the mediating role of health beliefs

Objective Health-promoting behaviors carry substantial significance for miners’ overall health and well-being. This study aimed to examine the association between cumulative risk (CR) and miners’ health-promoting behaviors and test the mediating role of health beliefs in this relationship. Methods Data were collected from a sequential survey conducted among 712 frontline miners (M age=41.7 ± 10.1 years) in China. The survey entailed online questionnaire measurements at three distinct time points, each spaced two weeks apart. This study utilized the conceptual model of health-promoting behaviors, the CR model, and structural equation modeling in the analysis of relationships. Results CR was negatively related to health-promoting behaviors, with a negative acceleration effect. CR was positively associated with perceived threat in a gradient effect, while negatively associated with perceived benefits in a gradient effect. Furthermore, CR was negatively related to self-efficacy, following a negative acceleration effect. Perceived threat, perceived benefits, and self-efficacy emerged as significant mediators in the relationship between CR and health-promoting behaviors. Conclusion This study highlights the critical role of considering both CR and health beliefs in shaping miners’ health-promoting behaviors. Understanding these dynamics is pivotal for developing interventions to enhance miners’ health and well-being.

Predicting fatigue failure in five‐axis machined ball‐end milled components through FKM local stress approach

AbstractComponents created with five‐axis machining show a multi‐scale surface character due to cusps created on the surface and feed and tool marks within the cusps. Therefore, it becomes difficult to incorporate the effects of surface character on fatigue life for such components. In this work, an Forschungskuratorium Maschinenbau (FKM) guideline is adapted to develop a fatigue prediction model which considers cusps as notches and marks within the cusps as surface roughness (characterized by parameter R10z). The assessment uses stresses obtained from an finite element analysis model to predict the fatigue life of components whilst considering stress concentration, stress gradient, mean stress, and surface roughness effects. When cusps are regarded as surface roughness within the conventional FKM approach, fatigue life is considerably underestimated. In comparison, fatigue life predictions that take into consideration the roughness within cusps and treat cusps as stress‐raising notches are closer to experimental life.

Fluid-Solid Interaction Analysis for Developing In-Situ Strain and Flow Sensors for Prosthetic Valve Monitoring.

Transcatheter aortic valve implantation (TAVI) was initially developed for adult patients, but there is a growing interest to expand this procedure to younger individuals with longer life expectancies. However, the gradual degradation of biological valve leaflets in transcatheter heart valves (THV) presents significant challenges for this extension. This study aimed to establish a multiphysics computational framework to analyze structural and flow measurements of TAVI and evaluate the integration of optical fiber and photoplethysmography (PPG) sensors for monitoring valve function. A two-way fluid-solid interaction (FSI) analysis was performed on an idealized aortic vessel before and after the virtual deployment of the SAPIEN 3 Ultra (S3) THV. Subsequently, an analytical analysis was conducted to estimate the PPG signal using computational flow predictions and to analyze the effect of different pressure gradients and distances between PPG sensors. Circumferential strain estimates from the embedded optical fiber in the FSI model were highest in the sinus of Valsalva; however, the optimal fiber positioning was found to be distal to the sino-tubular junction to minimize bending effects. The findings also demonstrated that positioning PPG sensors both upstream and downstream of the bioprosthesis can be used to effectively assess the pressure gradient across the valve. We concluded that computational modeling allows sensor design to quantify vessel wall strain and pressure gradients across valve leaflets, with the ultimate goal of developing low-cost monitoring systems for detecting valve deterioration.

Scale Differences and Gradient Effects of Local Climate Zone Spatial Pattern on Urban Heat Island Impact—A Case in Guangzhou’s Core Area

With the continuous development of cities, the surface urban heat island intensity (SUHII) is increasing, leading to the deterioration of the urban thermal environment, increasing energy consumption, and endangering the health of urban residents. Understanding the spatio-temporal scale difference and gradient effect of urban spatial patterns on the impact of SUHII is crucial for improving the climate resilience of cities and promoting sustainable urban development. This paper investigated the characteristics of SUHII changes at different time periods based on local climate zones (LCZs) and downscaled land surface temperature (LST) data. Meanwhile, landscape pattern indicators and the multiscale geographically weighted regression (MGWR) model were utilized to analyze the impacts of urban spatial patterns on SUHII at multiple spatial–temporal scales. The results indicated that the SUHII of each LCZ type exhibited diverse patterns in different time periods. High SUHII occurred in summer daytime and autumn nighttime. Compact and high-rise buildings (LCZ1/2/4) showed markedly higher SUHII during the daytime or nighttime, except for heavy industry. The extent of influence and the dominant factors of LCZ spatial patterns on SUHII exhibit obvious scale differences and gradient effects. At the regional scale, highly regular and compacted built-up areas tended to increase SUHII, while single and continuously distributed built-up areas had a greater impact on increasing SUHII. At the local scale, the impact of the PLAND (1/2/4/5/10) on SUHII exhibited a trend of diminishing from urban to suburban areas. In urban areas, the PLAND of LCZ 1, LCZ 2, and LCZ4 was the major factor affecting the increase in SUHII, whereas, in suburban areas, the PLAND of LCZ 2 and LCZ 10 was the major influencing factor on SUHII. The results can provide a scientific reference for mitigating urban heat island effects and constructing an ecologically ‘designed’ city.

WITHDRAWN: Examining the Effects of Land Use, Salinity Gradient, and Water Pollution on Greenhouse Gas Emissions in Urbanized Estuaries

Estuaries are significant contributors to greenhouse gases (GHGs) in waterways. However, the effects of human activities and ecological variables on GHG emissions in estuaries remain poorly understood. This study examines the patterns and causes of GHG emissions in the Scheldt Estuary, focusing on the roles of salinity, water contamination, and land use. The findings indicate that salinity negatively impacts the release of carbon dioxide (CO2) and nitrous oxide (N2O), likely due to reduced salt levels and cleaner water upstream. Water contamination's influence on GHG emissions was more pronounced in cleaner, upriver sites compared to saltier downstream locations. Specifically, CO2 emissions quadrupled, and N2O emissions tripled as water conditions worsened from healthy (near the mouth, bordered by agricultural land) to polluted (farther downstream, bordered by urban areas). Methane (CH4) emissions were significantly higher in aquatic locations than in salty sites. The reduced impact of contamination from downstream to the river mouth may be due to increasing population density. Urban sites emitted about twice as much CO2 and N2O as those in natural and industrial areas. Machine learning analysis also showed that fertilizers and organic enrichment, along with salinity, significantly increased GHG emissions. These results highlight the importance of understanding the interplay of salinity, water contamination, and land use in influencing GHG emissions in coastal ecosystems.

Reconstructing Prospective Intergenerational Educational Mobility in 12 Countries

In this article, we reconstruct prospective intergenerational educational mobility and explore fertility's role in this process for women born between 1925 and 1950 in 12 European countries. We do so by combining high-quality retrospective data (Generations and Gender Survey) and low-requirement prospective datasets using an inferential method developed and advanced in prior research. Our analysis shows that the negative educational fertility gradient partly compensates for the inequality in prospective mobility rates between lower and higher educated women and is most pronounced in high-inequality contexts. However, fertility's role is small and declining and thus does not account for much of the differences in mobility rates between countries. We also explore the relative importance of sibship size effects in mediating the effect of fertility gradient, finding it negligible. Finally, we explore the correspondence between prospective and retrospective estimates in the reconstruction of prospective mobility rates and suggest why the former, when available, must be preferred.

Assessment of selected ionospheric mapping functions using SF-PPP on different solar activities

In single-frequency precise point positioning (SF-PPP), the ionospheric delays provided by global ionosphere maps (GIMs) are in the vertical direction. Therefore, an ionospheric mapping function is applied to convert the vertical direction to the slant one. However, the performance of mapping functions (MF) applied in SF-PPP under different solar activities is unknown. Meanwhile, understanding their performance can help us better improve the accuracy of the ionospheric mapping function. For this purpose, three traditional ionospheric mapping functions, such as the standard single-layer model mapping function (SLM MF), the modified single-layer model mapping function (MSLM MF), and the Klobuchar MF, are evaluated. Additionally, the mapping function named SGG MF, which considers the effect of ionospheric gradients, is also assessed. The positioning results indicate that the SGG MF has an improvement of (50.3 %, 37.3 %), (31.7 %, 23.4 %), and (16.8 %, 13.3 %) compared with Klobuchar MF, SLM MF, and MSLM MF during the year (2014, 2021), respectively. The mean positioning errors of SLM MF, MSLM MF, and SGG MF are about (0.20 m, 0.05 m), (0.25 m, 0.10 m), and (0.30 m, 0.10 m) smaller than that of Klobuchar MF over high-/mid- latitude during the year (2014, 2021), while the values are (0.25 m, 0.20 m), (0.40 m, 0.35 m), and (0.55 m, 0.50 m) over low-latitude region. Furthermore, the correlation coefficients between positioning results and solar activities are (0.114, 0.354), (0.058, 0.324), (0.098, 0.295), and (0.235, 0.271) for Klobucahr MF, SLM MF, MSLM MF, and SGG MF during corresponding year.

Improved Design Method for Hypersonic Intakes Using Pressure-Corrected Osculating Axisymmetric Flows Method

The efficient design of air intake is crucial for high-speed airbreathing propulsion systems. This paper presents a novel design method that integrates the recently introduced internal conical flow M (ICFM) basic flowfield (Musa et al., “New Parent Flowfield for Streamline-Traced Intakes,” AIAA Journal, Vol. 61, No. 7, 2023, pp. 2906–2921) with the pressure-corrected osculating axisymmetric flows and streamline tracing techniques. The new design method takes into account the effects of lateral pressure gradients by incorporating pressure corrections into the original design method using crossflow velocity information from the ICFM flowfield. Additionally, new entrance and throat profiles are introduced for designing two hypersonic internal waverider intakes with shape transition. One intake is designed using the new method, and the other using the original method. Viscous simulations have been performed at design (i.e., Mach 6.0) and off-design (i.e., Mach 4.0 and 3.5) conditions. The results indicate that the pressure-corrected intake exhibits superior performance in terms of total pressure recovery and reduced flow distortion. This reveals that the new design method can achieve a smooth shape and efficient aerodynamic transitions between the intake entrance and throat. The new entrance and throat profiles realized better performance than the typical ones. The startability analysis reveals that the Van Wie curve controls the considered intakes. Thus, combining the pressure-corrected osculating axisymmetric flows with the ICFM flowfield enhances the performance of hypersonic intakes, making this approach a promising avenue for future hypersonic vehicles.

Numerical and experimental investigation of the supercooled large droplets icing of rotating spinner

The icing of aero-engine rotating components is more complex than traditional aircraft icing. A three-dimensional numerical method was developed based on the Eulerian method to study the supercooled large droplets icing of a rotating spinner. Typical dynamic behaviours of supercooled large droplets, such as deformation, breakup, rebound, and splashing, were considered. An icing thermodynamic model applicable to a rotating spinner was established by considering the effects of pressure gradient, air shear force, and centrifugal force on the flow of the water film. Meanwhile, an ice wind tunnel experiment on supercooled large droplets icing of a rotating spinner was carried out. The results showed that the maximum relative deviation of the simulated icing thickness at the cone tip is no more than 15% compared with the experimental result, and the icing thickness on the surface of the rotating spinner is basically consistent with the experimental result. Based on the three-dimensional numerical method developed in this study, the effects of the rotational speed, inflow velocity, and inflow temperature on the supercooled large droplets icing of a rotating spinner were investigated. As the rotational speed increases, the rebound and splashing of supercooled large droplets becomes more obvious, leading to an increase in the mass loss coefficient and a decrease in the collected mass of water droplets on the surface of the rotating spinner. Consequently, the icing thickness at the tail of the rotating spinner decreases with an increase in the rotational speed. Since the liquid water content in the environment is relatively low, water droplets freeze immediately after impacting the surface of the rotating spinner and rime ice is usually formed. When the inflow temperature is relatively high, overflow water exists and glaze ice is formed near the tip of the rotating spinner. The findings of this study can provide valuable support for the design and verification of anti-icing systems for aero-engine rotating spinner.

Improving the energy efficiency and riding comfort of high-speed trains across slopes by the optimized suspension control

As the link between cities, the high-speed train (HST) not only effectively enhances national and regional accessibility, but also induces much energy consumption. On the other hand, passengers have a higher requirement for riding comfort of HST than before. Considering the impacts of slope gradient on energy consumption and vertical carbody acceleration, this paper optimizes the scale factor of the damper controller depending on the running condition to juggle the energy efficiency and riding comfort when HST is across slopes. Firstly, the multibody dynamics simulation model of HST is established to evaluate the energy consumed by motion resistances and carbody vibrations. Then the Skyhook control strategy is applied to the secondary vertical damper of the vehicle model. The effects of vehicle speed, slope gradient, and scale factor of the Skyhook controller on energy saving and vertical carbody acceleration of HST are investigated. Based on the simulation results, the Gaussian process regression model is established to predict the vehicle performance and describe the bi-objective optimization problem. It is demonstrated that the optimized Skyhook control system can at most save energy consumed by motion resistances by 8.52 % or reduce vertical carbody acceleration by 37.14 % without sacrificing the other target. Finally, a comprehensive feasibility and economic analysis of the proposed control system is carried out to promote its practical implementation.