Search Results (94)

The subject of ship structural dynamics has faced new technological obstacles due to scientific and technological advancements, and one of the main concerns in related sectors is how to effectively reduce the vibration levels of different ships. This article focuses on the application scenarios of ship floating raft isolation systems, establishing a wave propagation model for acoustic black hole (ABH) structures based on the idea of the ABH effect. Then, a transfer matrix model for serially connected ABH structures is derived, which serves as a basis for subsequent structural designs. Second, the finite element method is used to study the energy distribution and vibration characteristics of a symmetrically distributed periodic non-uniform multi-level ABH structure. Meanwhile, it examines its bandgap distribution under a one-dimensional periodic arrangement and then investigates the vibration properties of non-uniform multi-level ABH thin-plate constructions with different periods from the perspective of engineering applications. Moreover, parameter optimization studies of non-uniform multi-level ABH structures with finite periods are carried out with an emphasis on engineering applications. The first step is to use the design space to determine the range of values for the parameters that need to be optimized. The hyper Latin cubic sampling method is then employed to select samples, and the EI criterion and PSO optimization algorithm are applied to add new samples to improve the Kriging surrogate model’s accuracy. When the optimal structural parameters have been determined, they are applied to the raft rib plate to verify the isolation effect of the non-uniform multi-level ABH structure by analyzing the vibration level difference at specific raft positions before and after embedding it. Full article

In the present study, the mechanical properties of high-strength steel rebar with different crossrib spacing that affect the bond behavior between steel rebar and concrete is investigated. To reveal the effects of crossrib spacing on the bond behavior of 630 MPa high-strength steel rebar (T63) in concrete, 42 bonding specimens were designed using T63 rebars and T63 rebars with increased crossrib spacing (TB63). The bond properties of two kinds of steel rebar with concrete were investigated by pull-out test and the failure modes, bond strengths, relative slippages, and bond-slip curves were obtained. Based on analysis of bond-slip curves, the applicability of the existing bond-slip constitutive model to describe T63 and TB63 rebars was discussed. It was found that 30–50% increase in crossrib spacing had little effect on the bond failure mode and bond strength of T63 rebar. The bond-slip curves of the two types of bonding specimens were similar and there is a 1.3 to 1.5-fold increase in peak slippage with TB63. The calculation method of critical bond length in Chinese code (GB 50010-2010) is applicable to T63 and TB63 rebars, and the bond-slip characteristics of T63 rebar with different crossrib spacings was reliably described by the bond-slip constitutive model. The research results can be used as the basis for the application of T63 reinforcement and can also be used as a reference for optimizing of rebar ribs outline. Full article

Negative Poisson’s ratio (NPR) reinforcement offers a novel solution to the usual trade-off between strength gains and ductility loss. Incorporating NPR into ultra-high-performance concrete (UHPC) effectively overcomes the ductility limitations of structural elements. However, the interfacial bonding between NPR reinforcement and UHPC is not sufficiently studied, especially its patterns and mechanisms, impeding the application of the materials. In this paper, the effects of nine design parameters (rebar type, prestrain, etc.) on the bond performance of NPR-UHPC through eccentric pull-out tests are investigated, and a quantitative discriminative indicator K_c for NPR-UHPC bond failure modes is established. The results showed that when K_c ≤ 4.3, 4.3 < K_c ≤ 5.64, and K_c ≥ 5.6, the NPR-UHPC specimens undergo splitting failure, splitting–pull-out failure, and pull-out failure, respectively. In terms of bonding with UHPC, the NPR bars outperform the HRB400 bars, and the HRB400 bars outperform the helical grooved (HG) bars. For the NPR bars, prestrain levels of 5.5%, 9.5%, and 22.0% decrease τ_u by 5.07%, 7.79%, and 17.01% and s_u by 7.00%, 15.88%, and 30.54%, respectively. Bond performance deteriorated with increasing rib spacing and decreasing rib height. Based on the test results, an artificial neural network (ANN) model is developed to accurately predict the critical embedded length l_cd and ultimate embedded length l_ud between NPR bars and UHPC. Moreover, the MAPE of the ANN model is only 53.9% of that of the regression model, while the RMSE is just 62.0%. Full article

In order to explore the axial compression performance of external steel rib ring restraint waste-steel-fiber-reinforced concrete-filled steel tubes (ERWCFSTs), 18 short-column axial compression tests were conducted. The effects of the number of rib rings, rib ring spacing, rib ring setting position, and waste steel fiber (WSF) content on the axial compression performance of the columns were analyzed. The results show that the concrete-filled steel tube (CFST) short columns with rib rings were strengthened, the specimens were mainly characterized by drum-shaped failure, and the buckling was concentrated between the rib rings. Without rib ring specimens, the steel tube is unable to resist the rapid increase in lateral expansion, leading to buckling initiation near the bottom of the specimens. The columns with rib rings exhibited a minimum increase of 32.5% and a maximum increase of 53.17% in load-bearing capacity compared to those without rib rings, with an average improvement of 37.78%. The columns achieved the best ductility when the rib ring spacing was 50 mm. When the rib ring spacing remained constant, columns with a number of rib rings no less than the height-to-diameter ratio (H/D) demonstrated more uniform stress distribution and optimal confinement effects. For a fixed number of rib rings, specimens with rib ring spacing between H/8 and H/4 showed significant improvements in both load-bearing capacity and ductility. The confinement effect was better when the rib rings were positioned in the middle of the column height rather than near the ends. The incorporation of WSF resulted in a minimum increase of 2.86% and a maximum increase of 10.49% in column load-bearing capacity, indicating limited enhancement. However, WSF improved the ductility performance of the columns by at least 10%. Combined with theoretical analysis and experimental data, a formula for calculating the bearing capacity of ERWCFSTs was established. Full article

Background: Early-onset scoliosis (EOS) is a severe spinal deformity that can compromise thoracic development and pulmonary function if left untreated. While Mehta casting is widely used to manage deformity non-surgically in young children, its effects on spinal and thoracic growth remain underexplored. Methods: In this retrospective case series, 15 children with EOS underwent serial elongation–derotation–flexion (EDF) Mehta casting. Radiographic assessments were performed pre-treatment, post-casting, and at follow-up, including measurements of Cobb angle, rib–vertebral angle difference (RVAD), Th1–Th12 spinal length, coronal chest width (CCW), and space available for lung (SAL). Growth rates were estimated based on the duration of treatment. Correlation analyses were conducted to examine associations between baseline deformity and structural outcomes. Results: Serial casting reduced the mean Cobb angle by 22.2° and RVAD by 15.5°. During treatment, measurable increases were observed in Th1–Th12 length (mean: 2.93 cm), CCW (1.12 cm), SAL-L (2.60 cm), and SAL-R (2.98 cm). Estimated annual growth was significantly greater in children with lower initial Cobb and RVAD values. In contrast, total casting duration showed no consistent correlation with growth outcomes. Conclusions: Mehta casting is effective not only in correcting spinal deformity but also in supporting thoracic and axial growth in children with EOS. Early application in flexible, less severe curves may optimize structural outcomes and preserve thoracic development during early growth. Full article

With the strengthening of international motor efficiency regulations, the new line-start synchronous reluctance motor (LS-SynRM), which does not require magnets or control units, is being studied to improve the efficiency of motors in industrial applications. However, the LS-SynRM features a complex structure with numerous design parameters, requiring the consideration of various factors such as electromagnetic performance, mechanical strength, starting capability, and ease of manufacturing. Additionally, starting capability analysis consumes a large amount of transient calculation time. The prototype stage typically comes after all simulation resources have been exhausted. The aim of this paper is to optimize the LS-SynRM by splitting the starting analysis and steady-state analysis, using a metamodel-based optimization method to quickly identify rotors of varying complexity (magnetic barriers and ribs) that meet steady-state efficiency and mechanical strength requirements. Finally, the rotor slot structure for starting is optimized within the magnetic barrier space. This approach significantly reduces the total optimization time from several weeks to just a few days. The final model obtained through the design process is analyzed using finite element analysis (FEA), and the results indicate that the target performance is achieved. To verify the FEA results, the final model is manufactured, and experiments are conducted. Full article

This paper presents an improved rapid prediction method for solving the full-space bistatic scattering sound field of underwater vehicles. The scattering sound field is represented as the product of the acoustic scattering transfer function and the sound source density function. By utilizing target surface mesh information and partial scattered sound pressure data as known inputs, the method predicts other bistatic scattering sound fields through numerical integration, matrix theory, and the least squares method. To reduce the data input required for predicting the scattering field, the monostatic to bistatic equivalence theorem is incorporated into the algorithm. A comparison with simulation results demonstrates that the proposed approach achieves favorable computational efficiency and reliability. Experimental tests on a double-layered ribbed cylindrical shell further validate the method’s performance. Full article

Photovoltaic (PV) wall panels are an integral part of Building-Integrated Photovoltaics (BIPV) and have great potential for development. However, inadequate heat dissipation can reduce power generation efficiency. To reduce the temperature of photovoltaic wall panels and improve the photovoltaic conversion efficiency, this paper constructs a computational fluid dynamics (CFD) numerical model of ventilated photovoltaic wall panels and verifies it, then simulates and analyzes the effects of three cavity structure forms on the thermal performance of photovoltaic wall panels and optimizes the dimensional parameters of the curved-ribbed cavity structure. The average surface temperatures of flat-plate, rectangular-ribbed, and arc-ribbed cavity structure PV wall panels were 59.42 °C, 57.56 °C, and 55.39 °C, respectively, under natural ventilation conditions. Among them, the arc-ribbed cavity structure PV wall panels have the best heat dissipation effect. Further studies have shown that the curvature, rib height, width, and spacing of the curved ribs significantly affect the heat dissipation performance of the photovoltaic panels. Compared to the flat-plate cavity structure, the parameter-optimized curved-rib cavity structure significantly reduces the average surface temperature of PV panels. As solar radiation intensity increases, the optimized structure’s heat dissipation effect strengthens, achieving a 6 °C temperature reduction at 1000 W/m² solar radiation. Full article

Space exploration and satellite communication demand lightweight, large-scale, and highly deployable structures. Inspired by the folding mechanism of frilled lizards and origami mechanisms, this study explores a deployable structure based on the single-vertex multi-crease origami (SVMCO) concept. The design focuses on crease distribution optimization to enhance deployment efficiency. A mathematical model analyzes the relationship between sector angles of three types of facets and structural performances, providing guidelines for achieving optimal deployment. Drawing from the rib patterns of frilled lizards, a rib support system for thick-panel mechanisms was designed and verified through a physical prototype. The structure achieves smooth-surface deployment with fewer supports, offering a lightweight and efficient solution for deployable systems. Full article

This study numerically investigates the thermal performance of a refrigerant-based battery thermal management system (BTMS) under various operating conditions. A validated numerical model is used to examine the effects of cooling channel rib configurations (rib spacing and rib angles) and refrigerant parameters (mass flow rate and saturation temperature) on battery thermal behavior. Additionally, the impact of discharge C-rates is analyzed. The results show that a rib spacing of 11 mm and a rib angle of 60° reduce the maximum battery temperature by 0.8 °C (cooling rate of 2%) and improve temperature uniformity, though at the cost of a 130% increase in pressure drop. Increasing the refrigerant mass flow rate lowers the maximum temperature by up to 10%, but its effect on temperature uniformity diminishes beyond 20 kg/h. A lower saturation temperature enhances cooling but increases internal temperature gradients, while a higher saturation temperature improves uniformity at the expense of a slightly higher maximum temperature. Under high discharge rates (12C), the system’s cooling capacity becomes limited, leading to significant temperature rises. These findings provide insights that can aid in optimizing BTMS design to balance cooling performance, energy efficiency, and temperature uniformity. Full article

Close-distance coal seams are common in underground mining, and their spacing is short, which produces strong mining disturbance. In instances where the upper seam has been mined and a goaf has formed, a notable issue arises during the lower seam’s mining, characterized by substantial deformation of the roadway along the goaf. Field exploration and three-dimensional geological modeling have revealed that the fourth and sixth working faces and pillar of seam No. 5 are all under seam No. 2’s goaf, with an average distance of 16.70 m. Simultaneously, the double compression effect of the pillar, induced by the linkage rotation of key blocks of the lower and upper seams, is analyzed. The induction mechanism and path of the large deformation are expounded. It is thus proposed that the pillar’s width should be determined by gob-side entry, driving beneath the goaf, with the roof near the pillar being cut off in advance to realize the path of cutting off the compressed pillar. Through the simulation comparison of five kinds of pillar width combined with engineering practice, it has been determined that the best width is 8 m, and the abutment pressure is distributed in a double-peak saddle shape, with the result that the load-bearing ability is notably significant. Through the comparative simulation of roof-cutting, it was found that roof-cutting helps the roof to collapse near the pillar-side and decreases the vertical stress peak to 16.46 MPa, the shear stress peak to 5.93 MPa, and the J₂ peak to 7.23 × 10¹³ Pa, which further alleviates the pressure on the pillar. In the field, the haulage roadway’s roof was cut by two-way shaped-charge blasting, and the sandy mudstone (5.90 m) was successfully cut off. Concurrently, anchor cable reinforcement was implemented on the roof and two ribs of the ventilation roadway in proximity to the pillar, thereby ensuring stabilization and mitigating the mining effect. The engineering research provides a case and scheme reference for the operation of gob-side entry driving beneath close-distance goafs worldwide. Full article

Due to the unique structural characteristics of loess, the strength of loess is significantly influenced by the water content. Therefore, different support parameters should be used for loess tunnels constructed in different water content strata. This paper takes the Fengshouling Tunnel as a case study, studying the reasonable primary support parameters under different water contents using the surrounding rock strength test, on-site monitoring, and numerical simulation software analysis. The research findings indicate that the strength of the surrounding rock is functionally related to its water content, with the cohesive force c exhibiting an exponential relationship and the angle of internal friction φ showing a linear relationship, and that the cohesive force c is more affected by changes in water content than the internal friction angle φ. The crown settlement of the loess tunnel exceeds the horizontal convergence, and the deformation behavior can be categorized into three distinct stages: rapid growth, continuous growth, and slow growth. Concurrently, the primary support structure mainly bears compressive stress. On the basis of considering structural safety and engineering economy, for tunnels with a general water content (10~17%), it is recommended to use I18 steel ribs spaced 60 cm apart and C25 shotcrete with a 24 cm thickness; for high water content (17~25%), it is recommended to use I20a steel ribs, also spaced 60 cm apart, complemented by C25 shotcrete increased to a 26 cm thickness; for situations with an extremely high water content (≥25%), it is recommended to reinforce the surrounding rock with curtain grouting and use steel ribs with the same 60 cm spacing, along with C25 shotcrete maintained at a 26 cm thickness. This paper proposes reasonable support parameters for loess tunnels applicable to different water contents. These results can provide guidance and specific reference for loess tunnels under different water content strata. Full article

Prestressed, precast composite panels are a type of building component that combines prestressing technology with composite materials; but, for most of them, it is difficult to balance structural stress performance and assembly efficiency. This paper proposes a series of novel bidirectional, prestressed, prefabricated, composite slabs, aiming to enhance their bidirectional force characteristics and assembly efficiency. By implanting a kind of specially designed concrete movable core rib with the same geometry as the cavity in the hollow-core slab at medium spacing, the transverse stressing performance of the structure is enhanced without affecting the unidirectional structural performance. Then, in the pre-set transverse apertures, several pieces of unidirectional, prestressed, precast hollow-core slabs that are implanted in the core mold are connected in series with high-strength strands and prestressed; finally, we obtain a bidirectional, prestressed, prefabricated composite slab. Two types of slabs (i.e., 3.3 m × 4.5 m and 4.5 m × 4.5 m) are selected and their mechanical behavior is investigated experimentally and by the finite element method, and the results are in good agreement. The proposed bidirectional, prestressed, precast composite slab not only has better overall bearing performance but also improves the structural stiffness and assembly rate, which can greatly improve the economic benefits and is of great significance for the popularization and application of assembled concrete structures. Full article

The control of hard roof conditions in underground coal mining is critical for ensuring mining safety and efficiency. Hard roof control remains a critical challenge in underground mining, particularly affecting mining safety and efficiency. Traditional support theories often show limitations in addressing the complex interactions between bolt spacing patterns and geological variability. This study focuses on the No. 10904 working face of Jingu Mine, where three distinct roof types are present: Type I (thick limestone roof, TLR, ≥1.2 m), Type II (moderate limestone roof, MLR, 0.5–1.2 m), and Type III (composite mudstone–limestone roof, CLR). Through FLAC3D numerical simulation and field validation, the mechanisms of bolt support under hard roof conditions were systematically investigated, and the optimization of bolt support parameters, including spacing, length, and pre-tension force, was conducted. The results indicate that: (1) when the ratio between lateral and row spacing approaches unity, reducing lateral spacing while increasing row spacing enhances support effectiveness, achieving 2 mm less roof subsidence with the 1.0 m × 1.5 m configuration compared to the 1.4 m × 0.8 m arrangement, despite a 21% reduction in bolt density; (2) an optimal rib bolt length of 1.8 m was determined, with support effectiveness diminishing beyond 2.0 m, and 1.5 m-long bolts reducing rib convergence by 15% compared to unsupported conditions; and (3) when the anchoring length exceeds 60% of the total bolt length, further increases in bolt length have minimal impact on deformation control under TLR, MLR, and CLR conditions. Field implementation of the optimized support scheme confirmed its effectiveness, with borehole television inspection showing no separation or fracturing within the monitored depth of 4 m in the roof strata. These findings provide practical guidelines for support design in similar geological settings, particularly for shallow-buried roadways with hard roof conditions. Full article

This paper presents the results of an optimization analysis of two types of thermal fluid channels. The selected geometries were evaluated according to the criterion of the Entropy Generation Minimization method as suggested by Adrian Bejan, with reference to a smooth pipe of the same diameter. The aim of this research was to assess the effectiveness of two channels that intensify heat transfer in different ways: with an insert (disrupting the flow in the pipe core) and with internal fins (disrupting the flow at the pipe wall), and to compare the results using the same criterion: the EGM method. The tested insert consisted of spaced streamline-shaped flow turbulizing the elements fixed in the axis of the pipe and spaced at equal distances from each other. The second channel was formed by making a right-angled triangle (rib profile) on the deformation of the pipe wall perimeter. Using computer modeling, the effect of the two geometric parameters of the above-mentioned channels on the flux of entropy generated was studied. These are (a) the diameter of the disturbing element (“droplet”) and the distance between these elements for a channel with a turbulent insert, and (b) the height of the rib and the longitudinal distance between them for a finned channel. The novelty resulting from the research is the discovery that the turbulization of the flow in the pipe wall boundary layer generates significantly less irreversible entropy than the disturbance of the flow in the pipe axis by the insert. Full article