Search

Abstract The effect of yttrium (Y) addition on the oxidation behavior of a Ni-based directionally solidified single-crystal superalloy is investigated in this study. Isothermal oxidation tests for samples with different levels of Y addition are conducted at 1100 °C in air. The Y content of the samples is determined by the actual pickup amount obtained from an Inductively Coupled Plasma-Atomic Emission Spectrometry test. It is discovered that the addition of Y increases the oxide resistance by the scale of an adhesive double-layer oxide, which is composed of Al2O3 and spinel Ni(Cr,Al)2O4. With 70 ppm of Y addition, the oxidation mass gain decreases from 12.6 g/m2 for the alloy without Y addition to 5.3 g/m2, and the oxidation rate decreases significantly. In addition, the internal nitride disappears after Y doping because of an increase in oxidation scale adherence and a decrease in oxidation products. In this study, the alloy with 660 ppm Y addition demonstrates the best oxidation resistance.

mong many microalgae species, certain euglenophytes stand out as excellent sources of valuable natural components with diverse biotechnological applications. This study focused on investigating the identity and potential utilizations of a green marine euglenophyte, namely EKoku01, isolated from the brackish Kokuba River in Naha City, Okinawa, Japan. Morphologically, cells of EKoku01 were 12-30m long and 8-10 m wide, displaying dynamic changes during euglenoid motility with a distinctively striated pellicular body. Notable features included two uneven flagella, an eyespot, and multiple green discoid chloroplasts. The 18S rDNA molecular phylogeny positioned Ekoku01 within Clade 1 of Eutreptiella, comprising strain CCMP389, CCMP-1594, and LIS 2000, which was distantly related to other known marine euglenophytes (i.e., the genus Eutreptia and Clade 2 of Eutreptiella). Based on the morphology and molecular phylogeny, EKoku01 was identified as Eutreptiella sp., representing the first recorded species of this genus in Okinawa, Japan. EKoku01 showed an optimum growth performance at 20 oC (max. =0.17 ± 0.037 day-1) and exhibited an unusually strong positive phototaxis response towards a light source. Its fatty acid (FAs) profile comprised predominantly saturated FAs (69.8%), polyunsaturated FAs (15.1%, with two omega-3 FAs), monounsaturated FAs (3.6%), and branched FAs (4.4%), while ~7.1% remaining unidentified. Based on its growth performance, FAs composition, and light sensitivity, we proposed several potential utilizations of this strain (e.g., as a source for nutraceutical, pharmaceutical, food, and aquaculture applications), including the use of EKoku01 as a model organism for developing an innovative light-driven cell concentration system based on phototaxis.

Chitosan is a potential raw material for marine cosmetics with antibacterial, anti-inflammatory properties and can stimulate collagen synthesis in the skin. This research aimed to obtain nano-sized chitosan (nanochitosan) from mud crab (Scylla sp.) shells and apply it as a cosmetic acne patch. The parameters used to characterize nanochitosan are particle size, polydispersity index, zeta potential and morphology. Meanwhile, the parameters of the Acne patch produced are characterized by physical appearance and ance bacterial activity. The results revealed that nanochitosan had an average size of 35.20 ±1.66 nm, the highest intensity of 11.70±1.25, polydispersity of 0.274±0.10, and zeta potential of 42.9±1.41 mV. The morphology of nanochitosan is in the form of broken rods, not hollow and irregular but uniform. Its elements include carbon, oxygen, magnesium, aluminum, phosphorus, and calcium. The acne patches resulting from the addition of 0 mg (K0), 50 mg (K1), 100 mg (K2), and 150 mg (K3) were opaque white, slightly transparent, smooth, elastic, and odorless. The thickness varies, namely, 0.014 ± 0.002 mm (K0), 0.017 ± 0.002 mm (K1), 0.022 ± 0.004 mm (K2), and 0.031 ± 0.005 mm (K3). The weight variations were 0.019 ± 0.001 mg (K0), 0.026 ± 0.005 mg (K1), 0.033 ± 0.002 mg (K2), and 0.047 ± 0.013 mg (K3). The moisture loss varied, namely, 7.525 ± 0.054% (K0), 3.201 ± 0.487% (K1), 2.741 ± 0.279% (K2), and 2.017 ± 0.290% (K3). Acne patches K1, K2, and K3 were proven to be able to inhibit the activity of acne bacteria Propionibacterium acnes (9.5 ± 0.25 mm, 10.67 ± 0.76 mm, and 9.17 ± 0.76 mm), Staphylococcus epidermidis (9.33 ± 1.15 mm, 13.67 ± 2.02 mm, and 8.67 ± 1.89 mm), and S. aureus (10.33 ± 0.25 mm, 11.83 ± 0.76 mm, and 8.66 ± 0.76 mm). This research succeeded in obtaining chitosan from crab shells (Scylla sp) in nano size and acne patches with the addition of nanochitosan effectively inhibited the growth of acne bacteria.

Bioflocculation, a microalgae harvesting method utilizing organisms like bacteria and microalgae as flocculant agents, necessitates careful selection and ratio determination of bioflocculant agents. This study seeks to ascertain the optimal balance of bioflocculant, Navicula sp., for metabolite production and harvesting efficiency in Arthrospira platensis culture. Spanning three oneweek cultivation stages, the research commences with A. platensis culture under varying salinities (0, 15, 25, and 35 ppt) in the first stage, followed by pH variations (9, 10, 11, and 12) in the second stage. The optimal salinity-pH combination identified in the first two stages is applied in the third stage, involving bioflocculant addition to culture and medium solutions at varying ratios (0.25:1, 0.5:1, 0.75:1, and 1:1 v/v). Precipitation efficiency and pigmentation were measured using spectrophotometry, while lipid content was determined by the Bligh Dyer extraction method. Carbohydrate content was assessed using the Phenol-Sulphuric Acid assay, and protein content was quantified using the Bradford protein assay. The findings indicate salinity, pH, and bioflocculant influence A. platensis growth, metabolite production, and harvesting efficiency. Optimal outcomes are achieved at 15 ppt salinity, pH 9, and a 1:1 ratio of bioflocculant, yielding 1.18x10-3 g of dry biomass, 3.56x105 cells/mL of cell density, 2.9x100 g/L of carbohydrates, 3.63x100 g/L of lipids, 9.97x10-3 mg/L of chlorophyll a+b, 8.71x10-1 mg/L of carotenoids, and 3.04x10-1 g/L of protein. These results suggest that salinity addition, high pH, and the addition of Navicula sp. as bioflocculant increase the harvesting process efficiency of A. platensis culture.

Calcium is an important macro-mineral that is really needed by the body. Calcium from fish bones can be an alternative source of calcium for those who are allergic to milk lactose which is usually used as calcium source. The weakness of fish bone calcium is that it still has a fishy odor, which reduces the hedonic value of products fortified with fish bone calcium. This research aims to determine the optimization of concentration and stirring time in citric acid to produce bio-calcium from catfish (Pangasius sp) bones with the best calcium content and hedonic characteristics using Response Surface Methodology (RSM). The citric acid concentration tested was a minimum of 0.25% and a maximum of 1% with stirring times of 30, 60 and 90 min. Data processing was carried out with the help of Design Expert 11 software. The recommended model is the quadratic model. The recommended optimization results for the bio-calcium production solution are a citric acid concentration of 0.25% and a soaking time of 30 min. Verification was carried out according to the optimization solution and gave yield results of 88.9%, particle size of 51.07 µm, calcium content 24.05; with a color hedonic value of 4.115, aroma 4.059 and overall 4.090 out of a maximum value of 5. XRD pattern showed no difference between fishbone powder and bio-calcium with degree crystallinity 57 and 56.2%, respectively. FTIR spectra showed that both fishbone powder and bio-calcium powder contained hydroxyapatite, however citric acid slightly removed protein due to absence of amide 1 peaks in bio-calcium powder. Citric acid at 0.25% for 30 min helped to increase the yield and reduced some organic compound to obtain bio-calcium powder. The proper concentration of citric acid and stirring time yielded catfish bone bio-calcium with higher calcium content and hedonic value.

Plastic debris and microplastic (MP) have been associated with marine pollution. The present study aimed to assess the MP accumulation in different organs (gut and gill) of 6 economically important fish species from two essential coastal areas, Jakarta Bay and Cirebon Bay. MP was isolated with NaCl, followed by the identification of MP profiles with digital microscope and Fourier Transform Infrared Spectroscopy (ATR-FTIR), respectively. The result showed that MP was found in all samples. Generally, MP concentration in fish from Cirebon Bay was slightly higher than that from Jakarta Bay, with benthic species more concentrated than pelagic fish in both sites. Microplastic was more concentrated on the gill of fish from Jakarta Bay, in contrast with Cirebon Bay. The predominantly MP in Jakarta Bay fish was fiber, while in Cirebon Bay was fragmented with minor granule and film in both locations. Polyethylene (PE), polyvinyl chloride (PVC), and polypropylene (PP) were the most dominant MP in the fish samples from both study areas. Microplastic size showed that the majority (65%) was the small size (1 mm), compared to the bigger one (1-5 mm), while blue, black, and red are the predominantly MP colors. This research supports the need to minimize plastic pollution in aquatic ecosystems to tackle the detrimental impact of MP accumulation to fish and human health. It is suggested to compare MP profiles on fish samples and in water or sediment compartments and identify the chemical constituents of MP.

Trypsin is a protease that breaks protein peptide bonds. Fish intestines can be used as an alternative raw material for trypsin. Trypsin enzymes from the intestines of different fish species have different characteristics. This study aimed to determine the characteristics and stability of trypsin enzyme in NaCl extracted from fish intestines based on differences in fish species. Trypsin activity was optimal at 50 °C and pH 8, with specific activity values of 0.5993 U/mg in rabbitfish, 0.3880 U/mg in sharks, and 0.6964 U/mg in flatfish. The maximum reaction speed (Vmax) was the highest for trypsin from the intestine of rabbitfish (0.2585 mmol/s), followed by flatfish (0.1042 mmol/s), and shark (0.0599 mmol/s). The lowest Km value was obtained for trypsin from sharks (0.4084 mM), followed by flatfish (1.0253 mM), and rabbitfish (4.5952 mM). Trypsin from the intestines of rabbitfish and flatfish was stable in NaCl solution (concentration 5-30%), as it can maintain a relative activity of more than 50%. In contrast, trypsin extracted from the intestines of milk fish had a relative activity below 21%. The average molecular weights of the three trypsin enzymes were 26.8, 27.2; and 21.9 kDa, respectively. Differences in the type of fish affected trypsin enzyme activity. Flatfish are omnivorous, and rabbitfish, as herbivores, have better enzyme activity values than sharks, as carnivores.

Abstract With the development of fluid-power transmission and control technology, electro-hydraulic-driven technology can significantly improve the load-carrying capacity, stiffness, and control accuracy of stabilization platforms. However, compared with mechanically driven platforms, the stiffness and damping of the fluid, as well as the coupling effect between the fluid and the structure need to be considered for electro-hydraulic-driven parallel stabilization platforms, making the modal and dynamic response characteristics of the mechanism more complex. With the aim of solving the aforementioned issues, we research the electro-hydraulic driven 3-UPS/S parallel stabilization platform considering the hinge stiffness. Moreover, the characteristic vibration equation of the mechanism is established using the virtual work principle. Subsequently, the variation characteristics of the natural frequency and the vibration response according to the position of the mechanism are analyzed based on the dynamic equation. Finally, the correctness of the model is verified by a modal test and Runge-Kutta methods. This study provides a theoretical basis for the dynamic design of electrohydraulic-driven parallel mechanisms.

Abstract In this study, a machine vision method is proposed to characterize 3D roughness of the textured surface on cylinder liner processed by plateau honing. The least absolute value (L∞) regression robust algorithm and Levenberg-Marquardt (LM) algorithm are employed to reconstruct image reference plane. On this basis, a single-hidden layer feedforward neural network (SLFNN) based on the extreme learning machine (ELM) is employed to model the relationship between high frequency information and 3D roughness. The characteristic parameters of Abbott-Firestone curve and 3D roughness measured by a confocal microscope are used to construct ELM-SLFNN prediction model for 3D roughness. The results indicate that the proposed method can effectively characterize 3D roughness of the textured surface of cylinder liner.

Abstract Threaded fasteners are one of the most commonly used connection methods for mechanical structures. Its primary function is to generate appropriate clamping forces and fasten the connected parts. An inappropriate preload can cause loosening, fatigue fracture, and other problems. This will affect the safety and reliability of mechanical equipment. The precise control of the preload has become a critical issue in mechanical assembly processes. Over the past few decades, various tightening measures and methods have been proposed to address this issue. However, many problems continue to exist with practical applications that have not been reviewed comprehensively and systematically. First, various control methods were summarized systematically, and their advantages and disadvantages in engineering applications were analyzed. Torque control is the most widely used tightening method owing to its simple operation and low cost. Therefore, the research on the torque control method was summarized systematically from three aspects: the torque–preload correlation formula, effective friction radius, and friction characteristics during tightening. In addition, the special circumstances that may increase preload uncertainty were discussed. Finally, based on a summary of the current research status, the prospects for future research were discussed. This study would aid researchers in extensively understanding the problems in preload control.

Abstract Isothermal forging stands as an effective technology for the production of large-scale titanium alloy multi-rib components. However, challenges have persisted, including die underfilling and strain concentration due to the complex material flow and heterogeneous deformation within the forging die cavity. While approaches centered on optimized billet designs have mitigated these challenges, uncertainties in process parameters continue to introduce unacceptable variations in forming accuracy and stability. To tackle this issue, this study introduced a multi-objective robust optimization approach for billet design, accounting for the multi-rib eigenstructure and potential uncertainties. The approach includes finite element (FE) modeling for analyzing the die-filling and strain inhomogeneity within the multi-rib eigenstructure. Furthermore, it integrated image acquisition perception and feed back technologies (IAPF) for real-time monitoring of material flow and filling sequences within die rib-grooves, validating the accuracy of the FE modeling. By incorporating dimensional parameters of the billet and uncertainty factors, including friction, draft angle, forming temperature, speed, and deviations in billet and die, quantitative analyses on the rib-groove filling and strain inhomogeneity with fluctuation were conducted. Subsequently, a dual-response surface model was developed for statistical analysis of the cavity filling and strain homogeneity. Finally, the robust optimization was processed using a non-dominated sorting genetic algorithm II (NSGA-II) and validated using the IAPF technologies. The proposed approach enables robust design enhancements for rib-groove filling and strain homogeneity in titanium alloy multi-rib components.

This paper employs the third-generation simulating waves nearshore (SWAN) ocean wave model to estimate and analyze storm waves induced by Typhoon Bolaven, focusing on its impact along the west coast and Jeju Island of Korea. Utilizing reanalyzed meteorological data from the Japan Meteorological Agency meso scale model (JMA-MSM), the study simulated storm waves from Typhoon Bolaven, which maintained its intensity up to high latitudes as it approached the Korean Peninsula in 2012. Validation of the SWAN model against observed wave data demonstrated a strong correlation, particularly in regions where wind speeds exceeded 20 m/s and wave heights surpassed 5 m. Results indicate significant storm wave heights across Jeju Island and Korea's west and southwest seas, with coastal grid points near islands recording storm wave heights exceeding 90% of the 50-year return period design wave heights. Notably, specific grid points near islands in the northern West Sea and southwest Jeju Island estimated storm wave heights at 90.22% and 91.48% of the design values, respectively. The paper highlights the increased uncertainty and vulnerability in coastal disaster predictions due to event-driven typhoons and emphasizes the need for enhanced accuracy and speed in typhoon wave predictions amid the escalating climate crisis.

In coastal video monitoring, the direct linear transform (DLT) method with ground control points (GCPs) is commonly used for geo-rectification. However, current practices often overlook the impact of GCP quantity, arrangement, and the geographical characteristics of beaches. To address this, we designed scenarios at Chuam Beach to evaluate how factors such as the distance from the camera to GCPs, the number of GCPs, and the height of each point affect the DLT method. Accuracy was assessed by calculating the root mean square error of the distance errors between the actual GCP coordinates and the image coordinates for each setting. This analysis aims to propose an optimal GCP placement method. Our results show that placing GCPs within 200 m of the camera ensures high accuracy with few points, whereas positioning them at strategic heights enhances shoreline extraction. However, since only fixed cameras were used in this study, factors like varying heights, orientations, and resolutions could not be considered. Based on data from a single location, we propose an optimal method for GCP placement that takes into account distance, number, and height using the DLT method.

Autonomous underwater vehicles (AUVs) have a limited bandwidth for real-time communication, limiting rapid responses to unexpected obstacles. This study addressed how AUVs can navigate to a target without a pre-existing obstacle map by generating one in real-time and avoiding obstacles. This paper proposes using forward-looking sonar with an occupancy grid map (OGM) for real-time obstacle mapping and a potential field algorithm for avoiding obstacles. The OGM segments the map into grids, updating the obstacle probability of each cell for precise, quick mapping. The potential field algorithm attracts the AUV towards the target and uses repulsive forces from obstacles for path planning, enhancing computational efficiency in a dynamic environment. Experiments were conducted in coastal waters with obstacles to verify the real-time obstacle mapping and avoidance algorithm. Despite the high noise in sonar data, the experimental results confirmed effective obstacle mapping and avoidance. The OGM-based potential field algorithm was computationally efficient, suitable for single-board computers, and demonstrated proper parameter adjustments through two distinct scenarios. The experiments also identified some of challenges, such as dynamic changes in detection rates, propulsion bubbles, and changes in repulsive forces caused by sudden obstacles. An enhanced algorithm to address these issues is currently under development.

In this study, a submerged breakwater with effective wave control and eco-friendly characteristics is developed and proposed. Hydraulic experiments are conducted to compare the hydraulic performance of a submerged breakwater and an eco-friendly double-row submerged breakwater. The hydraulic characteristics are analyzed based on wave reflections and the transmission-splitting method for each experimental cross-section. This splitting technique utilizes Goda’s two-point method, which employs the spectra of two irregular superposed wave fields. In addition, the reliability of the results obtained from the hydraulic experiments is discussed by comparing the results with empirical formulas. The eco-friendly double-row submerged breakwater features approximately half the width of a typical submerged breakwater. Nevertheless, its transmission coefficient (KT) is approximately 20% more effective, and the difference in the average reflection coefficient (KR) values between the two is approximately 0.17. Moreover, the dissipation coefficient (KD) shows a generally similar trend. Based on these experimental results, the hydraulic performance of the eco-friendly double-row submerged breakwater is more efficient regarding wave control, compared with a typical submerged breakwater. These hydraulic characteristics confirm that the numerical model developed for the eco-friendly double-row submerged breakwater accurately reproduces the KT, KR, and KD values within ±5%.

Abstract Anti-rollover is a critical factor to consider when planning the motion of autonomous heavy trucks. This paper proposed a method for autonomous heavy trucks to generate a path that avoids collisions and minimizes rollover risk. The corresponding rollover index is deduced from a 5-DOF heavy truck dynamic model that includes longitudinal motion, lateral motion, yaw motion, sprung mass roll motion, unsprung mass roll motion, and an anti-rollover artificial potential field (APF) is proposed based on this. The motion planning method, which is based on model predictive control (MPC), combines trajectory tracking, anti-rollover APF, and the improved obstacle avoidance APF and considers the truck dynamics constraints, obstacle avoidance, and anti-rollover. Furthermore, by using game theory, the coefficients of the two APF functions are optimised, and an optimal path is planned. The effectiveness of the optimised motion planning method is demonstrated in a variety of scenarios. The results demonstrate that the optimised motion planning method can effectively and efficiently avoid collisions and prevent rollover.

Abstract Collisions between objects are a relatively common phenomenon in nature. Analyses of collision processes can greatly contribute to solving problems such as impact-rub faults and particle impacts. The coefficient of restitution is a critical parameter in the analysis of collision processes. Many experiments have shown that the coefficient of restitution is closely related to the plate thickness, and the smaller the plate thickness, the more inaccurate the coefficient of restitution predicted by the existing model, which seriously affects the process of collision analysis. To remedy this shortcoming, this paper proposes a plate thickness influence factor with the ratio of sphere diameter to plate thickness as the variable. The plate thickness influence factor can optimize the coefficient of restitution model to effectively predict the coefficient of restitution of impacting elastoplastic spheres with finite plate thickness. Finally, the validity of the new model is verified using a large amount of experimental data.

Abstract The current research of sandwich structures under dynamic loading mainly focus on the response characteristic of structure. The micro-topology of core layers would sufficiently influence the property of sandwich structure. However, the micro deformation and topology mechanism of structural deformation and energy absorption are unclear. In this paper, based on the bi-directional evolutionary structural optimization method and periodic base cell (PBC) technology, a topology optimization frame work is proposed to optimize the core layer of sandwich beams. The objective of the present optimization problem is to maximize shear stiffness of PBC with a volume constraint. The effects of the volume fraction, filter radius, and initial PBC aspect ratio on the micro-topology of the core were discussed. The dynamic response process, core compression, and energy absorption capacity of the sandwich beams under blast impact loading were analyzed by the finite element method. The results demonstrated that the over-pressure action stage was coupled with the core compression stage. Under the same loading and mass per unit area, the sandwich beam with a 20% volume fraction core layer had the best blast resistance. The filter radius has a slight effect on the shear stiffness and blast resistances of the sandwich beams. But increasing the filter radius could slightly improve the bending stiffness. Upon changing the initial PBC aspect ratio, there are three ways for PBC evolution: The first is to change the angle between the adjacent bars, the second is to further form holes in the bars, and the third is to combine the first two ways. However, not all three ways can improve the energy absorption capacity of the structure. Changing the aspect ratio of the PBC arbitrarily may lead to worse results. More studies are necessary for further detailed optimization. This research proposes a new topology sandwich beam structure by micro-topology optimization, which has sufficient shear stiffness. The micro mechanism of structural energy absorption is clarified, it is significant for structural energy absorption design.

Abstract Automated fiber placement (AFP) enables the efficient and precise fabrication of complex-shaped aerospace composite structures with lightweight and high-performance properties. However, due to the excessive compression on the inner edge of the tow placed along the curved trajectory, the resulting defects represented by buckling and wrinkles in spatial tow steering can induce poor manufacturing accuracy and quality degradation of products. In this paper, a theoretical model of tow buckling based on the first-order shear deformation laminate theory, linear elastic adhesion interface and Hertz compaction contact theory is proposed to analyze the formation mechanism of the wrinkles and predict the formation of defects by solving the critical radius of the trajectory, and finite element analysis involving the cohesive zone modeling (CZM) is innovated to simulate the local buckling state of the steered tow in AFP. Additionally, numerical parametric studies and experimental results indicate that mechanical properties and geometric parameters of the prepreg, the curvature of the placement trajectory and critical process parameters have a significant impact on buckling formation, and optimization of process parameters can achieve effective suppression of placement defects. This research proposes a theoretical modeling method for tow buckling, and conducts in-depth research on defect formation and suppression methods based on finite element simulation and placement experiments.

Abstract The surface morphology and roughness of a workpiece are crucial parameters in grinding processes. Accurate prediction of these parameters is essential for maintaining the workpiece’s surface integrity. However, the randomness of abrasive grain shapes and workpiece surface formation behaviors poses significant challenges, and accuracy in current physical mechanism-based predictive models is needed. To address this problem, by using the random plane method and accounting for the random morphology and distribution of abrasive grains, this paper proposes a novel method to model CBN grinding wheels and predict workpiece surface roughness. First, a kinematic model of a single abrasive grain is developed to accurately capture the three-dimensional morphology of the grinding wheel. Next, by formulating an elastic deformation and formation model of the workpiece surface based on Hertz theory, the variation in grinding arc length at different grinding depths is revealed. Subsequently, a predictive model for the surface morphology of the workpiece ground by a single abrasive grain is devised. This model integrates the normal distribution model of abrasive grain size and the spatial distribution model of abrasive grain positions, to elucidate how the circumferential and axial distribution of abrasive grains influences workpiece surface formation. Lastly, by integrating the dynamic effective abrasive grain model, a predictive model for the surface morphology and roughness of the grinding wheel is established. To examine the impact of changing the grit size of the grinding wheel and grinding depth on workpiece surface roughness, and to validate the accuracy of the model, experiments are conducted. Results indicate that the predicted three-dimensional morphology of the grinding wheel and workpiece surfaces closely matches the actual grinding wheel and ground workpiece surfaces, with surface roughness prediction deviations as small as 2.3%.

Abstract The establishment of an elastostatic stiffness model for over constrained parallel manipulators (PMs), particularly those with over constrained subclosed loops, poses a challenge while ensuring numerical stability. This study addresses this issue by proposing a systematic elastostatic stiffness model based on matrix structural analysis (MSA) and independent displacement coordinates (IDCs) extraction techniques. To begin, the closed-loop PM is transformed into an open-loop PM by eliminating constraints. A subassembly element is then introduced, which considers the flexibility of both rods and joints. This approach helps circumvent the numerical instability typically encountered with traditional constraint equations. The IDCs and analytical constraint equations of nodes constrained by various joints are summarized in the appendix, utilizing multipoint constraint theory and singularity analysis, all unified within a single coordinate frame. Subsequently, the open-loop mechanism is efficiently closed by referencing the constraint equations presented in the appendix, alongside its elastostatic model. The proposed method proves to be both modeling and computationally efficient due to the comprehensive summary of the constraint equations in the Appendix, eliminating the need for additional equations. An example utilizing an over constrained subclosed loops demonstrate the application of the proposed method. In conclusion, the model proposed in this study enriches the theory of elastostatic stiffness modeling of PMs and provides an effective solution for stiffness modeling challenges they present.

Abstract Cam-lobe radial-piston hydraulic motors are widely used as rotation driving units for various marine machinery owing to their ultrahigh output torque (more than 100 kN m). A multi-row cam roller bearing (MCRB) is the key component that directly determines the fatigue life of a cam-lobe radial-piston hydraulic motor. However, compact geometry and complex loads render MCRB susceptible to fatigue failure, highlighting the need for an optimized MCRB to achieve longer fatigue life and higher reliability. Therefore, this study proposes an innovative geometry optimization method for an MCRB to improve its fatigue life. In this method, a quasi-static model was developed to calculate the load distribution, with the fatigue life of the MCRB calculated using both basic dynamic loading and load distribution. Subsequently, a genetic algorithm was used to obtain the optimized geometry parameters, which significantly improved the fatigue life of the MCRB. Finally, a loading test was conducted on a hydraulic motor installed with both the initial and optimized MCRB to validate the effectiveness of the proposed optimization method. This study provides a theoretical guideline for optimizing the design of MCRB, thereby increasing the fatigue life of hydraulic motors.

Abstract The high-speed on/off valve (HSV) serves as the fundamental component responsible for generating discrete fluids within digital hydraulic systems. As the switching frequency of the HSV increases, the properties of the generated discrete fluid approach those of continuous fluids. Therefore, a higher frequency response characteristic of HSV is the key to ensure the control accuracy of digital hydraulic systems. However, the current research mainly focuses on its dynamic performance, but neglect its FRC. This paper presents a theoretical analysis demonstrating that the FRC of the HSV can be enhanced by minimizing its switching time. The maximum switching frequency (MSF) is mainly determined by opening dynamic performance when HSV operates with low switching duty ratio (SDR), whereas the closing dynamic performance limits the MSF when HSV operates with high SDR. Building upon these findings, the pre-excitation control algorithm (PECA) is proposed to reduce the switching time of the HSV, and consequently enhance its FRC. Experimental results demonstrate that PECA shortens the opening delay time of HSV by 1.12 ms, the closing delay time by 2.54 ms, and the closing moving time by 0.47 ms in comparison to the existing advanced control algorithms. As a result, a larger MSF of 417 Hz and a wider controllable SDR range from 20% to 70% were achieved at a switching frequency of 250 Hz. Thus, the proposed PFCA in this paper has been verified as an effective and promising approach for enhancing the control performance of digital hydraulic systems.

Abstract Titanium and its alloys have been widely applied in many biomedical fields because of its excellent mechanical properties, corrosion resistance and good biocompatibility. However, problems such as rejection, shedding and infection will occur after titanium alloy implantation due to the low biological activity of titanium alloy surface. The structures with specific functions, which can enhance osseointegration and antibacterial properties, are fabricated on the surface of titanium implants to improve the biological activity between the titanium implants and human tissues. This paper presents a comprehensive review of recent developments and applications of surface functional structure in titanium and titanium alloy implants. The applications of surface functional structure on different titanium and titanium alloy implants are introduced, and their manufacturing technologies are summarized and compared. Furthermore, the fabrication of various surface functional structures used for titanium and titanium alloy implants is reviewed and analyzed in detail. Finally, the challenges affecting the development of surface functional structures applied in titanium and titanium alloy implants are outlined, and recommendations for future research are presented.

Abstract Ceramic cutting inserts are a type of cutting tool commonly used in high-speed metal cutting applications. However, the wear of these inserts caused by friction between the workpiece and cutting inserts limits their overall effectiveness. In order to improve the tool life and reduce wear, this study introduces an emerging method called magnetic field-assisted batch polishing (MABP) for simultaneously polishing multiple ceramic cutting inserts. Several polishing experiments were conducted under different conditions, and the wear characteristics were clarified by cutting S136H steel. The results showed that after 15 min of polishing, the surface roughness at the flank face, edge, and nose of the inserts was reduced to below 2.5 nm, 6.25 nm, and 45.8 nm, respectively. Furthermore, the nose radii of the inserts did not change significantly, and there were no significant changes in the weight percentage of elements before and after polishing. Additionally, the tool life of the batch polished inserts was found to be up to 1.75 times longer than that of unpolished inserts. These findings suggest that the MABP method is an effective way to mass polish ceramic cutting inserts, resulting in significantly reduced tool wear. Furthermore, this novel method offers new possibilities for polishing other tools.

Abstract Ensuring high product quality is of paramount importance in pharmaceutical drug manufacturing, as it is subject to rigorous regulatory practices. This study presents a research focused on the development of an on-line detection method and system for identifying surface defects in pharmaceutical products packaged in aluminum-plastic blisters. Firstly, the aluminum-plastic blister packages exhibit multi-scale features and inter-class indistinction. To address this, the deep semantic network with boundary refinement (DSN-BR) model is proposed, which leverages semantic segmentation domain knowledge, to accurately segment the defects in pixel level. Additionally, a specialized image acquisition module that minimizes the impact of ambient light is established, ensuring high-quality image capture. Finally, the image acquisition module, image detection module, and data management module are designed to construct a comprehensive online surface defect detection system. To validate the effectiveness of our approach, we employ a real dataset for instance verification on the implemented system. The experimental results substantiate the outstanding performance of the DSN-BR, achieving the mean intersection over union (MIoU) of 90.5%. Furthermore, the proposed system achieves an inference speed of up to 14.12 f/s, while attaining an F1-Score of 98.25%. These results demonstrate that the system meets the actual needs of the enterprise and provides theoretical and methodological support for intelligent inspection of product surface quality. By standardizing the control process of pharmaceutical manufacturing and improving the management capability of the manufacturing process, our approach holds significant market application prospects.

Abstract Ultrasonic scalpel design for minimally invasive surgical procedures is mainly focused on optimizing cutting performance. However, an important issue is the low fatigue life of traditional ultrasonic scalpels, which affects their long-term reliability and effectiveness and creates hidden dangers for surgery. In this study, a multi-objective optimal design for the cutting performance and fatigue life of ultrasonic scalpels was proposed using finite element analysis and fatigue simulation. The optimal design parameters of resonance frequency and amplitude were determined. By setting the transition fillet and keeping the gain structure away from the node position to enable the scalpel to have a high service life with excellent cutting performance. The frequency modulation method of setting the vibration node bosses at the node position and setting the vibration antinode grooves at the antinode position was compared. Then, the mechanism of the influence of various design elements, such as tip, shank, node position, and antinode position, on the resonance frequency, amplitude, and fatigue life of the ultrasonic scalpel was analyzed, and the optimal design principles of the ultrasonic scalpel were obtained. The proposed ultrasonic scalpel design was confirmed by simulations, impedance measurements, and liver tissue cutting experiments, demonstrating its feasibility and enhanced performance. This research introduces innovative design strategies to improve the fatigue life and performance of ultrasonic scalpels to address an important issue in minimally invasive surgery.

Abstract Enhancing ride comfort has always constituted a crucial focus in the design and research of modern tracked vehicles, heavily reliant on the driving system’s performance. While the road wheel is a key component of the driving system, traditional road wheels predominantly adopt a solid structure, exhibiting subpar adhesion performance and damping effects, thereby falling short of meeting the demands for high-speed, stable, and long-distance driving in tracked vehicles. Addressing this issue, this paper proposes a novel type of flexible road wheel (FRW) characterized by a catenary construction. The study investigates the ride comfort of tracked vehicles equipped with flexible road wheels by integrating finite element and vehicle dynamic. First, three-dimensional (3D) finite element (FE) models of both flexible and rigid road wheels are established, considering material and contact nonlinearities. These models are validated through a wheel radial loading test. Based on the validated FE model, the paper uncovers the relationship between load and radial deformation of the road wheel, forming the basis for a nonlinear mathematical model. Subsequently, a half-car model of a tracked vehicle with seven degrees of freedom is established using Newton’s second law. A random road model, considering the track effect and employing white noise, is constructed. The study concludes by examining the ride comfort of tracked vehicles equipped with flexible and rigid road wheels under various speeds and road grades. The results demonstrate that, in comparison to the rigid road wheel (RRW), the flexible road wheel enhances the ride comfort of tracked vehicles on randomly uneven roads. This research provides a theoretical foundation for the implementation of flexible road wheels in tracked vehicles.

Abstract The encapsulation of lunar samples is a core research area in the third phase of the Chinese Lunar Exploration Program. The seal assembly, opening and closing mechanism (OCM), and locking mechanism are the core components of the encapsulation device of the lunar samples, and the requirements of a tight seal, lightweight, and low power make the design of these core components difficult. In this study, a combined sealing assembly, OCM, and locking mechanism were investigated for the device. The sealing architecture consists of rubber and an Ag-In alloy, and a theory was built to analyze the seal. Experiments of the electroplate Au coating on the knife-edge revealed that the hermetic seal can be significantly improved. The driving principle for coaxial double-helical pairs was investigated and used to design the OCM. Moreover, a locking mechanism was created using an electric initiating explosive device with orifice damping. By optimizing the design, the output parameters were adjusted to meet the requirements of the lunar explorer. The experimental results showed that the helium leak rate of the test pieces were not more than 5 × 10−11 Pa·m3·s−1, the minimum power of the OCM was 0.3 W, and the total weight of the principle prototype was 2.9 kg. The explosive driven locking mechanism has low impact. This investigation solved the difficulties in achieving tight seal, light weight, and low power for the lunar explorer, and the results can also be used to explore other extraterrestrial objects in the future.

Abstract The crack-closure effect is a crucial factor that affects the crack growth rate and should be considered in simulation analysis and testing. A mixed-mode I + II loading fatigue crack growth test was performed using EA4T axle steel specimens. The variation of the plastic-induced crack closure (PICC) effect and the roughness-induced crack closure (RICC) effect during crack deflection in the mixed-mode is examined in this study. The results show that the load perpendicular to the crack propagation direction hinders the slip effect caused by the load parallel to the crack propagation direction under mixed-mode loading, and the crack deflection is an intuitive manifestation of the interaction between the PICC and RICC. The proportion of the R A value change on the crack side caused by contact friction was reduced by the interaction between PICC and RICC. The roughness of the crack surface before and after the crack deflection is different, and the spatial torsion crack surface is formed during the crack propagation process. With the increase of the crack length, the roughness of the fracture surface increases. During the crack deflection process, the PICC value fluctuates around 0.2, and the RICC value is increased to 0.15.

Abstract Adding nanoparticles can significantly improve the tribological properties of lubricants. However, there is a lack of understanding regarding the influence of nanoparticle shape on lubrication performance. In this work, the influence of diamond nanoparticles (DNPs) on the tribological properties of lubricants is investigated through friction experiments. Additionally, the friction characteristics of lubricants regarding ellipsoidal particle shape are investigated using molecular dynamics (MD) simulations. The results show that DNPs can drastically lower the lubricant's friction coefficient μ from 0.21 to 0.117. The shearing process reveals that as the aspect ratio (α) of the nanoparticles approaches 1.0, the friction performance improves, and wear on the wall diminishes. At the same time, the shape of the nanoparticles tends to be spherical. When 0.85 ≤ α ≤ 1.0, rolling is ellipsoidal particles' main form of motion, and the friction force changes according to a periodic sinusoidal law. In the range of 0.80 ≤ α < 0.85, ellipsoidal particles primarily exhibit sliding as the dominant movement mode. As α decreases within this range, the friction force progressively increases. The friction coefficient μ calculated through MD simulation is 0.128, which is consistent with the experimental data.

Los objetivos del trabajo son evaluar la evolución temporal y espacial de la recarga al Acuífero del Cuaternario del Campo de Cartagena desde 1970 a 2022 y generar mapas de entrada para un modelo numérico de flujo de agua subterránea. Para alcanzarlos se han recopilado datos meteorológicos, se ha compilado y contrastado la información disponible sobre los usos de suelo, poniendo especial atención en la evolución temporal de la distribución espacial, se ha calculado la recarga con el software VisualBALAN y se han generado mapas de recarga que reflejan la evolución espacial y temporal durante el periodo simulado, con el apoyo de QGIS. La recarga calculada se ha calibrado y validado con éxito con series piezométricas temporales. La recarga total media calculada es 91 hm3 año-1 para todo el periodo; los valores extremos son 24 hm3 en 1978 y 172 hm3 en 2008. Esto se traduce en un coeficiente de recarga promedio del 16%, un valor mínimo del 8% y un máximo del 24%.

Debido a su durabilidad, versatilidad y bajo coste, los productos plásticos resultan fundamentales en la sociedad actual; sin embargo, estas mismas propiedades, responsables de su gran popularidad, también convierten a estos materiales en una amenaza medioambiental, provocando serios problemas entre los que destaca la liberación de microplásticos (MPs). Los MPs, definidos como partículas poliméricas con un tamaño inferior a 5 mm, son muy diversos en cuanto a composición, tamaño y forma, siendo capaces además de transportar sobre su superficie otros contaminantes y microorganismos, lo que incrementa los potenciales efectos adversos de estas micropartículas. Aunque los MPs se encuentran de manera ubicua en todo el planeta, su presencia es notoria en los ecosistemas acuáticos, especialmente los marinos, ya que las masas de agua naturales reciben la gran mayoría de los plásticos vertidos al medioambiente. Recientemente, la biorremediación ha sido propuesta como una interesante alternativa para luchar contra la creciente problemática derivada de la contaminación plástica; por ello, el objetivo de la presente revisión bibliográfica es analizar las posibles vías de eliminación de los MPs de origen fósil y no biodegradables en entornos acuáticos, mediante bacterias, hongos y organismos superiores, recopilando los últimos avances en este campo.

La agricultura es una de las principales fuentes de contaminación difusa, cuya contaminación por nitrógeno y sedimentos de las son los principales impactos ambientales. Es por ello, que una adecuada gestión de estas zonas es necesaria. El presente estudio se llevó a cabo en la cuenca más meridional del Mar Menor, que se encuentra amenazado por la exportación difusa de nutrientes y sedimentos. Es por ello que este estudio evalúa la efectividad de varias actuaciones basadas en la Ley 3/2020, de recuperación y protección del Mar Menor para el control de las descargas de nitrógeno y sedimentos a la laguna. Los resultados de estas simulaciones mostraron que con el cumplimiento completo de la Ley 3/2020 es posible reducir de forma significativa la producción de sedimentos a la laguna, así como la exportación de nitrógeno en superficie y la lixiviación de nitratos.

En el presente artículo se evalúa la eficiencia de bioportadores de polietileno tereftalato (PET) reciclado para el tratamiento de aguas residuales municipales en reactores MBBR. En marco del objetivo, se caracterizó el agua residual y se estabilizó el proceso en los biorreactores experimentales hasta el desarrollo de la biopelícula. Posteriormente, se operó el sistema experimental a diferentes proporciones de llenado (50% y 30%) y tiempos de retención hidráulica (TRH) de 6 y 8 horas. Finalmente se analizó la calidad del efluente mediante la medición de temperatura, pH, DQO, DBO5, SST y Turbidez. Como resultado, se logró la formación de una biopelícula esponjosa poco compacta y delgada en tres semanas, con una remoción promedio de 81.80% para DBO5, 78.44% para DQO, 85.96% para SST y 94.13% para turbidez. Además, se comprobó que el factor de llenado tuvo efectos estadísticamente significativos y contribuyó más en la remoción de DBO5 y SST, mientras que el TRH fue más influyente en la remoción de DQO. Se concluye que los bioportadores de PET son eficientes y, según estándares normados, el efluente tratado es apto para ser vertido a un cuerpo hídrico natural y/o ser reutilizado para el riego de áreas verdes restringidas al público o de contacto indirecto u ocasional.

La escasez de agua y la creciente demanda de alimentos imponen la utilización de tecnologías más eficientes en el regadío. Por tal motivo, se abordaron los fundamentos hídricos e hidráulicos del riego subsuperficial a demanda mediante vasos comunicantes (RSVC), estudio de caso cultivo de col rizada. El sistema estuvo compuesto por un depósito de agua, una cubeta con carga hidráulica constante, una línea de derivación, laterales de riego, emisores y vasos de cultivo. La pérdida de carga en el sistema, para el lateral más alejado, fue 7.38491 mm.c.a., permitiendo operar a presiones muy bajas sin requerimiento energético. Debido a la continuidad hidráulica, generada por la tasa evapotranspirativa, los cultivos no sufrieron estrés hídrico, obteniéndose un rendimiento promedio de 360 g de materia fresca/planta, con una eficiencia de uso del agua de 22.38 g/l, rendimientos favorables cuando se compara con otros estudios.

Abstract Physical assistive robotics are oriented to support and improve functional capacities of people. In physical rehabilitation, robots are indeed useful for functional recovery of affected limb. However, there are still open questions related to technological aspects. This work presents a systematic review of upper limb rehabilitation robotics in order to analyze and establish technological challenges and future directions in this area. A bibliometric analysis was performed for the systematic literature review. Literature from the last six years, conducted between August 2020 and May 2021, was reviewed. The methodology for the literature search and a bibliometric analysis of the metadata are presented. After a preliminary search resulted in 820 articles, a total of 66 articles were included. A concurrency network and bibliographic analysis were provided. And an analysis of occurrences, taxonomy, and rehabilitation robotics reported in the literature is presented. This review aims to provide to the scientific community an overview of the state of the art in assistive robotics for upper limb physical rehabilitation. The literature analysis allows access to a gap of unexplored options to define the technological prospects applied to upper limb physical rehabilitation robotics.

Abstract Efficiency of calculating a dynamic response is an important point of the compliant mechanism for posture adjustment. Dynamic modeling with low orders of a 2R1T compliant parallel mechanism is studied in the paper. The mechanism with two out-of-plane rotational and one lifting degrees of freedom (DoFs) plays an important role in posture adjustment. Based on elastic beam theory, the stiffness matrix and mass matrix of the beam element are established where the moment of inertia is considered. To improve solving efficiency, a dynamic model with low orders of the mechanism is established based on a modified modal synthesis method. Firstly, each branch of the RPR type mechanism is divided into a substructure. Subsequently, a set of hypothetical modes of each substructure is obtained based on the C-B method. Finally, dynamic equation of the whole mechanism is established by the substructure assembly. A dynamic experiment is conducted to verify the dynamic characteristics of the compliant mechanism.

Abstract With the growing interest in utilizing Mg and austenitic stainless steel (ASS) in the automotive sector, joining them together in three-sheet configuration is inevitable. However, achieving this task presents considerable challenges due to the large differences in their physical, metallurgical and mechanical properties. To overcome these challenges, the feasibility of using weld-bonding to join Mg alloy/ASS/ASS was investigated. The nugget formation, interface characteristics, microstructure and mechanical properties of the joints were investigated. The results show that the connection between the Mg alloy and upper ASS was achieved through the combined effect of the cured adhesive and weld-brazing in the weld zone. On the other hand, a metallurgical bond was formed at the ASS/ASS interface. The Mg nugget microstructure exhibited fine columar grains composed predominantly of primary α-Mg grains along with a eutectic mixture of α-Mg and β-Mg17Al12. The nugget formed at the ASS/ASS interface consisted largely of columnar grains of austenite, with some equiaxed dendritic grains formed at the centerline of the joint. The weld-bonded joints exhibited an average peak load and energy absorption of about 8.5 kN and 17 J, respectively (the conventional RSW joints failed with minimal or no load application). The failure mode of the joints changed with increasing welding current from interfacial failure via the Mg nugget/upper ASS interface to partial interfacial failure (part of the Mg nugget was pulled out of the Mg sheet). Both failure modes were accompanied by cohesive failure in the adhesive zone.

Abstract Vibration quality is a vital indicator for assessing the progress of modern equipment. The dynamic vibration absorber (DVA) based on the acoustic black hole (ABH) feature is a new passive control method that manipulates waves. It offers efficient energy focalization and broad-spectrum vibration suppression, making it highly promising for applications in large equipment such as aircraft, trains, and ships. Despite previous advancements in ABH-DVA development, certain challenges remain, particularly in ensuring effective coupling with host structures during control. To address these issues, this study proposes a partitioned ABH-featured dynamic vibration absorber (PABH-DVA) with partitions in the radial direction of the disc. By employing a plate as the host structure, simulations and experiments were conducted, demonstrating that the PABH-DVA outperforms the original symmetric ABH-DVA in terms of damping performance. The study also calculated and compared the coupling coefficients of the two ABH-DVAs to uncover the mechanism behind the enhanced damping. Simulation results revealed that the PABH-DVA exhibits more coupled modes, occasionally with lower coupling coefficients than the symmetric ABH-DVA. The influence of frequency ratio and modal mass was further analyzed to explain the reasons behind the PABH-DVA's superior damping performance. Additionally, the study discussed the impact of the number of slits and their orientation. This research further explains the coupling mechanism between the ABH-DVA and the controlled structure, and provides new ideas for the further application of ABH in engineering.

Abstract Mesh reflector antennas are widely used in space tasks owing to their light weight, high surface accuracy, and large folding ratio. They are stowed during launch and then fully deployed in orbit to form a mesh reflector that transmits signals. Smooth deployment is essential for duty services; therefore, accurate and efficient dynamic modeling and analysis of the deployment process are essential. One major challenge is depicting time-varying resistance of the cable network and capturing the cable-truss coupling behavior during the deployment process. This paper proposes a general dynamic analysis methodology for cable-truss coupling. Considering the topological diversity and geometric nonlinearity, the cable network’s equilibrium equation is derived, and an explicit expression of the time-varying tension of the boundary cables, which provides the main resistance in truss deployment, is obtained. The deployment dynamic model is established, which considers the coupling effect between the soft cables and deployable truss. The effects of the antenna’s driving modes and parameters on the dynamic deployment performance were investigated. A scaled prototype was manufactured, and the deployment experiment was conducted to verify the accuracy of the proposed modeling method. The proposed methodology is suitable for general cable antennas with arbitrary topologies and parameters, providing theoretical guidance for the dynamic performance evaluation of antenna driving schemes.

Abstract This study analysed the failure of dissimilar metal welds (DMWs) between ferritic heat resistant steels and austenitic stainless steels and investigated its influencing factors by means of numerical simulation, microstructure characterization and mechanical property test. Under the long-term high-temperature service condition in practical power plant, the DMW failure mode was along the interface between nickel-based weld metal (WM) and ferritic heat resistant steel, and the failure mechanism was stress/strain concentration, microstructure degradation and oxidation coupling acting on the interface. The numerical simulation results show that interface stress/strain concentration was due to the differences in coefficient of thermal expansion and creep strength, and the degree of stress/strain concentration was related to service time. The ferrite band formed at the WM/ferritic steel interface was prone to cracking, attracting the fracture along the interface. The interface crack allowed oxidation to develop along the WM/ferritic steel interface. During long-term service, the interface stress/strain concentration, microstructure and oxidation all evolved, which synergistically promoted interface failure of DMW. However, only under the long-term service of low stress conditions could trigger the interface failure of DMW. Meanwhile, long-term service would reduce the mechanical strength and plasticity of DMW.

Abstract In order to predict the damage behaviours of 3D-printed continuous carbon fibre (CCF) reinforced composites, when additional short carbon fibre (SCF) composite components are employed for continuous printing or special functionality, a novel path-dependent progressive failure (PDPF) numerical approach is developed. First, a progressive failure model using Hashin failure criteria with continuum damage mechanics to account for the damage initiation and evaluation of 3D-printed CCF reinforced polyamide (PA) composites is developed, based on actual fibre placement trajectories with physical measurements of 3D-printed CCF/PA constituents. Meanwhile, an elastic-plastic model is employed to predict the plastic damage behaviours of SCF/PA parts. Then, the accuracy of the PDPF model was validated so as to study 3D-printed CCF/PA composites with either negative Poisson’s ratio or high stiffness. The results demonstrate that the proposed PDPF model can achieve higher prediction accuracies in mechanical properties of these 3D-printed CCF/PA composites. Mechanism analyses show that the stress distribution is generally aggregated in the CCF areas along the fibre placement paths, and the shear damage and matrix tensile/compressive damage are the key damage modes. This study provides a new approach with valuable information for characterising complex 3D-printed continuous fibre-matrix composites with variable mechanical properties and multiple constituents.

Abstract A dual-arm nursing robot can gently lift patients and transfer them between a bed and a wheelchair. With its lightweight design, high load-bearing capacity, and smooth surface, the coupled-drive joint is particularly well suited for these robots. However, the coupled nature of the joint disrupts the direct linear relationship between the input and output torques, posing challenges for dynamic modeling and practical applications. This study investigated the transmission mechanism of this joint and employed the Lagrangian method to construct a dynamic model of its internal dynamics. Building on this foundation, the Newton-Euler method was used to develop a dynamic model for the entire robotic arm. A continuously differentiable friction model was incorporated to reduce the vibrations caused by speed transitions to zero. An experimental method was designed to compensate for gravity, inertia, and modeling errors to identify the parameters of the friction model. This method establishes a mapping relationship between the friction force and motor current. In addition, a Fourier series-based excitation trajectory was developed to facilitate the identification of the dynamic model parameters of the robotic arm. Trajectory tracking experiments were conducted during the experimental validation phase, demonstrating the high accuracy of the dynamic model and the parameter identification method for the robotic arm. This study presents a dynamic modeling and parameter identification method for coupled-drive joint robotic arms, thereby establishing a foundation for motion control in humanoid nursing robots.

Abstract The current research on the integrity of critical structures of rail vehicles mainly focuses on the design stage, which needs an effective method for assessing the service state. This paper proposes a framework for predicting the remaining useful life (RUL) of in-service structures with and without visible cracks. The hypothetical distribution and delay time models were used to apply the equivalent crack growth life data of heavy-duty railway cast steel knuckles, which revealed the evolution characteristics of the crack length and life scores of the knuckle under different fracture failure modes. The results indicate that the method effectively predicts the RUL of service knuckles in different failure modes based on the cumulative failure probability curves for different locations and surface crack lengths. This study proposes an RUL prediction framework that supports the dynamic overhaul and state maintenance of knuckle fatigue cracks.

Abstract Profile shift is a highly effective technique for optimizing the performance of spur gear transmission systems. However, tooth surface wear is inevitable during gear meshing due to inadequate lubrication and long-term operation. Both profile shift and tooth surface wear (TSW) can impact the meshing characteristics by altering the involute tooth profile. In this study, a tooth stiffness model of spur gears that incorporates profile shift, TSW, tooth deformation, tooth contact deformation, fillet-foundation deformation, and gear body structure coupling is established. This model efficiently and accurately determines the time-varying mesh stiffness (TVMS). Additionally, an improved wear depth prediction method for spur gears is developed, which takes into consideration the mutually prime teeth numbers and more accurately reflects actual gear meshing conditions. Results show that consideration of the mutual prime of teeth numbers will have a certain impact on the TSW process. Furthermore, the finite element method (FEM) is employed to accurately verify the values of TVMS and load sharing ratio (LSR) of profile-shifted gears and worn gears. This study quantitatively analyzes the effect of profile shift on the surface wear process, which suggests that gear profile shift can partially alleviate the negative effects of TSW. The contribution of this study provides valuable insights into the design and maintenance of spur gear systems.

Abstract Prognostics and health management (PHM) has gotten considerable attention in the background of Industry 4.0. Battery PHM contributes to the reliable and safe operation of electric devices. Nevertheless, relevant reviews are still continuously updated over time. In this paper, we browsed extensive literature related to battery PHM from 2018 to 2023 and summarized advances in battery PHM field, including battery testing and public datasets, fault diagnosis and prediction methods, health status estimation and health management methods. The last topic includes state of health estimation methods, remaining useful life prediction methods and predictive maintenance methods. Each of these categories is introduced and discussed in details. Based on this survey, we accordingly discuss challenges left to battery PHM, and provide future research opportunities. This research systematically reviews recent research about battery PHM from the perspective of key PHM steps and provide some valuable prospects for researchers and practitioners.

Abstract As a new grinding and maintenance technology, rail belt grinding shows significant advantages in many applications. The dynamic characteristics of the rail belt grinding vehicle largely determines its grinding performance and service life. In order to explore the vibration control method of the rail grinding vehicle with abrasive belt, the vibration response changes in structural optimization and lightweight design are respectively analyzed through transient response and random vibration simulations in this paper. Firstly, the transient response simulation analysis of the rail grinding vehicle with abrasive belt is carried out under operating conditions and non-operating conditions. Secondly, the vibration control of the grinding vehicle is implemented by setting vibration isolation elements, optimizing the structure, and increasing damping. Thirdly, in order to further explore the dynamic characteristics of the rail grinding vehicle, the random vibration simulation analysis of the grinding vehicle is carried out under the condition of the horizontal irregularity of the American AAR6 track. Finally, by replacing the Q235 steel frame material with 7075 aluminum alloy and LA43M magnesium alloy, both vibration control and lightweight design can be achieved simultaneously. The results of transient dynamic response analysis show that the acceleration of most positions in the two working conditions exceeds the standard value in GB/T 17426-1998 standard. By optimizing the structure of the grinding vehicle in three ways, the average vibration acceleration of the whole car is reduced by about 55.1% from 15.6 m/s2 to 7.0 m/s2. The results of random vibration analysis show that the grinding vehicle with Q235 steel frame does not meet the safety conditions of $$3\sigma$$ 3 σ . By changing frame material, the maximum vibration stress of the vehicle can be reduced from 240.7 MPa to 160.0 MPa and the weight of the grinding vehicle is reduced by about 21.7% from 1500 kg to 1175 kg. The modal analysis results indicate that the vibration control of the grinding vehicle can be realized by optimizing the structure and replacing the materials with lower stiffness under the premise of ensuring the overall strength. The study provides the basis for the development of lightweight, diversified and efficient rail grinding equipment.

Abstract To ensure an accurate selection of rolling guide shoe materials, an analysis of the intricate relationship between linear speed and wear is imperative. Finite element simulations and experimental measurements are employed to evaluate four distinct types of materials: polyurethane, rubber, polytetrafluoroethylene (PTFE), and nylon. The speed-index of each material is measured, serving as a preparation for subsequent analysis. Furthermore, the velocity-wear factor is determined, providing insights into the resilience and durability of the material across varying speeds. Additionally, a wear model tailored specifically for viscoelastic bodies is explored, which is pivotal in understanding the wear mechanisms within the material. Leveraging this model, wear predictions are made under higher speed conditions, facilitating the choice of material for rolling guide shoes. To validate the accuracy of the model, the predicted degree of wear is compared with experimental data, ensuring its alignment with both theoretical principles and real-world performance. This comprehensive analysis has verified the effectiveness of the model in the selection of materials under high-speed conditions, thereby offering confidence in its reliability and ensuring optimal performance.

Abstract In practice, simultaneous impact localization and time history reconstruction can hardly be achieved, due to the ill-posed and under-determined problems induced by the constrained and harsh measuring conditions. Although $$\ell_{1}$$ ℓ 1 regularization can be used to obtain sparse solutions, it tends to underestimate solution amplitudes as a biased estimator. To address this issue, a novel impact force identification method with $$\ell_{p}$$ ℓ p regularization is proposed in this paper, using the alternating direction method of multipliers (ADMM). By decomposing the complex primal problem into sub-problems solvable in parallel via proximal operators, ADMM can address the challenge effectively. To mitigate the sensitivity to regularization parameters, an adaptive regularization parameter is derived based on the K-sparsity strategy. Then, an ADMM-based sparse regularization method is developed, which is capable of handling $$\ell_{p}$$ ℓ p regularization with arbitrary p values using adaptively-updated parameters. The effectiveness and performance of the proposed method are validated on an aircraft skin-like composite structure. Additionally, an investigation into the optimal p value for achieving high-accuracy solutions via $$\ell_{p}$$ ℓ p regularization is conducted. It turns out that $$\ell_{0.6}$$ ℓ 0.6 regularization consistently yields sparser and more accurate solutions for impact force identification compared to the classic $$\ell_{1}$$ ℓ 1 regularization method. The impact force identification method proposed in this paper can simultaneously reconstruct impact time history with high accuracy and accurately localize the impact using an under-determined sensor configuration.