Search Results (669)

Scheuermann’s kyphosis (SK) is a rigid dorsal kyphosis of unclear pathophysiological origin. The aim of this review is to summarise current theories and both clinical and experimental findings regarding the underlying mechanisms of SK. Emerging evidence highlights the significant role of excessive mechanical loading as a major contributor to defective growth of the cartilaginous vertebral endplate. This is associated with the formation of Schmorl’s nodes, disruption of the ring apophysis, and compromised intervertebral disc integrity—ultimately resulting in vertebral body wedging and thickening of the anterior longitudinal ligament. In addition, numerous studies have investigated the genetic contribution and underlying molecular mechanisms involved in the pathogenesis of SK. Recent in vivo findings suggest an association between asymmetric mechanosensory activation of cerebrospinal fluid (CSF), contacting neurons, and defective Reissner fibre signalling, which may contribute to abnormal spinal morphogenesis in the sagittal thoracic plane. These findings indicate a potential link between altered CSF dynamics and the development of SK. Taken together, the evidence supports a multifactorial aetiology, with both genetic and biomechanical factors playing central roles in the development of Scheuermann’s kyphosis. The interpretation of the underlying pathophysiological mechanism could result in the early detection of the subjects that may have genetical predisposition for SK appearance and the development of target molecular treatments in order to counter the progression of the deformity. Full article

There is a significant demand for flexibility in steam turbines, including rapid cold starts and load changes, as well as operation at low partial loads. Both industrial plants and systems for electricity and heat generation are impacted. These new operating modes result in complex, asymmetric temperature fields and additional thermally induced stresses. These lead to casing deformations, which affect blade tip gap and casing flange sealing integrity. The exact progression of heat flux and heat transfer coefficients within the cavities of steam turbines remains unclear. The current methods used in the calculation departments rely on simplified, averaged estimates, despite the presence of complex flow phenomena. These include swirling inflows, temperature gradients, impinging jets, unsteady turbulence, and vortex formation. This paper presents a novel sensor and its thermal measurements taken on a full-scale steam turbine test rig. Numerical calculations were performed concurrently. The results were validated by measurements. Additionally, the distribution of the heat transfer coefficient along the cavity was analysed. The rule of L’Hôpital was applied at specific locations. A method for handling axial variation in the heat transfer coefficient is also proposed. Measurements were taken under real-life conditions with a full-scale test rig at MAN Energy Solutions SE, Oberhausen, with steam parameters of 400 °C and 30 bar. The results at various operating points are presented. Full article

Openings are often introduced in continuous reinforced concrete (RC) deep beams to accommodate utility services, which can compromise their structural capacity. This paper presents a numerical investigation—via nonlinear finite element (FE) modeling—into the effects of post-construction rectangular openings in continuous high-strength concrete (HSC) deep beams. A previously tested two-span continuous HSC deep beam with rectangular openings was used for model validation and subsequently adopted in a parametric study, maintaining consistent beam and opening dimensions. The study focuses on the influence of opening location, both symmetric and asymmetric, at mid-depth within critical shear and flexural zones of the two-span continuous deep beam. Key parameters analyzed include load-carrying capacity, support reactions, initial and post-cracking stiffness, reinforcement stresses, and concrete stress distribution. Results indicate that mid-depth openings located in flexure-critical regions have minimal impact, causing only a 3–5% reduction in load-carrying capacity and negligible changes in stress behavior. However, when openings intersect the primary strut paths, reductions in capacity ranged from 17% to 53%, depending on the number and location of the openings (i.e., crossing external or internal struts). Furthermore, symmetric placement of openings was found to significantly mitigate performance degradation compared to asymmetric configurations. These findings provide design insights that enable safe incorporation of service openings without excessive material use, thereby promoting more sustainable and resource-efficient concrete construction. Full article

Asymmetric friction, that is, different friction forces resisting sliding in opposing directions, works as a rectifier, transferring the applied oscillations into unidirectional motion. Locomotion of devices based on asymmetric friction is investigated by considering a model system consisting of an asymmetric friction block connected to a symmetric friction block by a spring. The symmetric friction block models the resistance to the movement by the environment. It is found that under harmonic oscillation, the system displays two distinct types of motion: Recurrent Movement (stick-slip-type movement) and Sub-Frictional Movement. The Recurrent Movement occurs when the inertia force is sufficient to overcome the frictional force. In this case, the system with asymmetric friction exhibits unidirectional locomotion, while the system with only symmetric friction oscillates about a fixed point. The Sub-Frictional Movement occurs when the inertia is insufficient to overcome the frictional force. Then the symmetric friction block moves against the asymmetric friction block and sufficiently loads the spring to enable some movement of the system. Thus, motion is generated even when the external forces are below the static friction threshold. These types of motion have been found to exhibit different types of spectral fallout: while the Recurrent Movement produces a typically observed frictional fallout 1/ω, where ω is the frequency, the Sub-Frictional Movement produces a stronger 1/ω² fallout, only observed in the development of an oblique fracture in rocks under compression. This discovery can shed light on mechanisms of rock failure in compression. Understanding of the unidirectional movement induced by asymmetric friction can be instrumental in designing novel locomotion devices that can move in narrow channels or fractures in the Earth’s crust or in extraterrestrial bodies utilising the (renewable) energy of external vibrations. Full article

This paper proposes a small-signal model of a DC–DC parallel resonant converter operating in continuous conduction mode based on asymmetric pulse-width modulation (APWM) under light-load conditions. The parallel resonant converter enables soft switching and no-load control over a wide load range because the resonant capacitor is connected in parallel with the load. However, the resonant energy required for soft switching is already sufficient, and the current flowing through the resonant tank is independent of the load magnitude; therefore, as the load decreases, the energy that is not delivered to the load and instead circulates meaninglessly inside the resonant tank increases. This results in conduction loss and reduced efficiency. To address this issue, APWM with a fixed switching frequency is required, which reduces circulating energy and improves efficiency under light-load conditions. Precise small-signal modeling is required to optimize the APWM controller. Unlike PFM or PSFB, APWM includes not only sine components but also DC and cosine components in the control signal due to its asymmetric switching characteristics, and this study proposes a small-signal model that can relatively accurately reflect these multi-harmonic characteristics. The proposed model is derived based on the Extended Describing Function (EDF) concept, and the derived transfer function is useful for systematically analyzing the dynamic characteristics of the APWM-based parallel resonant converter. In addition, it provides information that can systematically analyze the dynamic characteristics of various APWM-based resonant converters and control signals that reflect various harmonic characteristics, and it can be widely applied to future control design and analysis studies. The validity of the model is verified through MATLAB (R2025b) and PLECS (4.7.5) switching-model simulations and experimental results, confirming its high accuracy and practicality. Full article

Gallium-based liquid metals have been extensively studied in the field of biomedical engineering, including applications in tumor and inflammatory disease therapy, as well as targeted drug delivery. Among these, leveraging the photothermal effect of gallium liquid metals enables effective treatment of heat-sensitive cells in tumor regions and enhances the diffusion capability of liquid metal microdroplets. However, research on the active treatment of ulcerative colitis (UC) using photothermal therapy with liquid metals remains unexplored. This study focuses on constructing an active composite colloidal motor based on gallium indium liquid metal alloy, using liquid metal microdroplets as the core. Through layer-by-layer assembly of polyelectrolytes, a liquid metal active droplet loaded with the drug mesalazine (5-aminosalicylic acid), named as LMAD-A was developed. Under asymmetric light fields generated by NIR-II light source irradiation, LMAD-A exhibits autonomous locomotion, achieving an effective diffusion coefficient more than 800 times greater than that of Brownian motion in liquid metal microdroplets of similar size. Furthermore, LMAD-A demonstrates phototactic behavior, moving toward the NIR light source autonomously. Through in vitro and in vivo experiments in mice, it was verified that LMAD-A can aggregate, deform, and fuse in the mouse colon under photothermal effects, leading to enhanced release of the loaded drug. In simulated treatments, LMAD-A significantly alleviated DSS-induced colitis in mice, confirming the targeted therapeutic capability of active liquid metal microdroplets as an active therapeutic agent in UC-affected regions. Full article

Gas well deliquification is a key technology for mitigating liquid loading and restoring or enhancing production capacity in ultra-deep, high-temperature, and high-pressure gas wells. The abnormal corrosion behavior observed in the gas lift tubing of the Well X-1 oilfield in western China, within the 50–70 °C interval (1000–1500 m), was investigated. By analyzing the asymmetric wall thinning and axial groove morphology on the inner surface of tubing and then establishing a two-dimensional model of the vertical wellbore, the gas–liquid flow behavior and associated corrosion mechanisms were also elucidated. Results indicate that the flow pattern evolves from slug flow at the bottomhole, through a transitional pattern below the gas lift valve, to annular-mist flow at and above the valve. The wall shear stress peaks at the gas lift valve coupled with the significantly higher fluid velocity above the valve, which markedly elevates the corrosion rate. In this regime, the resultant annular-mist flow features a high-velocity gas core carrying entrained droplets, whose impingement synergistically enhances electrochemical corrosion, forming severe groove-like morphology along the inner tubing wall. Therefore, the corrosion in this well is attributed to the synergistic effect of the mechano-electrochemical coupling between multiphase flow and electrochemical processes on the inner surface of the tubing. Full article

Background: This scoping review systematically maps and synthesises contemporary literature on the biomechanics of active below-knee prosthetic devices, focusing on gait kinematics, kinetics, energy expenditure, and muscle activation. It further evaluates design advancements, including powered ankle–foot prostheses and variable impedance systems, that seek to emulate physiological ankle function and enhance mobility outcomes for transtibial amputees. Methods: This review followed the PRISMA-ScR guidelines. A comprehensive literature search was conducted on ScienceDirect, PubMed and IEEE Xplore for studies published between 2013 and 2023. Search terms were structured according to the Population, Intervention, Comparator, and Outcome (PICO) framework. From 971 identified articles, 27 peer-reviewed studies were found to meet the inclusion criteria between January 2013 and December 2023. Data were extracted on biomechanical parameters, prosthetic design characteristics, and participant demographics to identify prevailing trends and research gaps. This scoping review was registered with Research Registry under the following registration number: reviewregistry 2055. Results: The reviewed studies demonstrate that active below-knee prosthetic systems substantially improve gait symmetry and ankle joint range of motion compared with passive devices. However, compensatory trunk and pelvic movements persist, indicating that full restoration of natural gait mechanics remains incomplete. Metabolic efficiency varied considerably across studies, influenced by device design, control strategies, and user adaptation. Notably, the literature exhibits a pronounced gender imbalance, with only 10.7% female participants, and a reliance on controlled laboratory conditions, limiting ecological validity. Conclusions: Active prosthetic technologies represent a significant advancement in lower-limb rehabilitation. Nevertheless, complete biomechanical normalisation has yet to be achieved. Future research should focus on long-term, real-world evaluations using larger, more diverse cohorts and adaptive technologies such as variable impedance actuators and multi-level control systems to reduce asymmetrical loading and optimise gait efficiency. Full article

This paper proposes a hybrid rigid–flexible wing design that enables large-area folding and reconfiguration. Based on elasticity theory and fabric constitutive equations, a surface-outward mechanical model incorporating mesoscale weave structures was developed for plain-woven wing membranes. To address the degradation of the model under low-prestress conditions, a more accurate second-order nonlinear model for the out-of-plane mechanics of wing membranes was further developed. This paper developed a dual-axis tensile fixture and, through conducting load-bearing performance experiments on wing membrane elements, verified that the improved theoretical model possesses a certain degree of predictive accuracy. A dual-axis tensile fixture was designed, and load-bearing tests on membrane elements were conducted to verify that the improved theoretical model provides reasonable predictive accuracy. To investigate how pre-tensioning regulates membrane stiffness, the variation in out-of-plane stiffness under symmetric and asymmetric prestress conditions was analysed. A prestressing strategy prioritising the principal-modulus direction is proposed, providing theoretical guidance for prestress application in wing membranes. Based on these findings, a prototype rigid–flexible composite wing with a “membrane-scaffold” structure was fabricated and tested. Full article

The highly directional narrow-beam operation in mmWave networks, while effective at suppressing interference, lacks adaptability to dynamic traffic variations and blockages compared to D-TDD and JT schemes. D-TDD efficiently mitigates DL–UL cross-interference during asymmetric traffic. At the same time, joint transmission coordinates multiple base stations to deliver phase-aligned signals, converting interference into useful combined power and ensuring stable links under dynamic slot changes. However, these adaptive regimes are often overlooked in recent mmWave designs, leading to degraded communication performance. This work proposes D-TDD-based cooperative caching (DTCC) mmWave networks, where randomly distributed base stations with local caches enhance reliability and reduce backhaul load. Closed-form expressions for the cache hit probability and the average content success probability (ASP) are derived under the proposed DTCC framework. Popularity-based caching strategies with both equal and variable file sizes are analysed to maximise network-level performance. The simulation results validate that the proposed DTCC framework consistently enhances ASP in dense small-cell deployments, offering notable reliability gains over conventional single-BS (SBS) and static TDD (S-TDD)-based cooperative caching approaches. Full article

A touch-off explosion on concrete slabs is considered one of the simplest yet most destructive forms of adversarial loading on building elements. It causes far greater damage than explosions occurring at a distance. The impact is usually concentrated in a small area, leading to surface cratering, scabbing of concrete, and even tearing or rupture of the reinforcement. Studies available on the behavior of reinforced concrete (RC) slabs under touch-off (contact) and standoff explosions commonly indicate that the maximum damage occurs when the blast is applied to the center of the slab. This observation raises an important question about how the position of an explosive charge, especially relative to the free edge of the slab, affects the overall damage pattern in slabs supported on only two sides with clamped supports. This study uses a modeling strategy combining Eulerian and Lagrangian domains using the finite element tools of Abaqus Explicit v2020 to examine the behavior of a square slab supported on two sides with clamped ends subjected to blast loads at different positions, ranging from the center to the free edge and beyond, under touch-off explosion conditions. The behavior of concrete was captured using the Concrete Damage Plasticity model, while the reinforcement was represented with the Johnson–Cook model. Effects of strain rate were included by applying calibrated dynamic increase factors. The developed numerical model is validated first with experimental data available in the published literature for the case where the explosive charge is positioned at the slab’s center, showing a very close agreement with the reported results. Along with the central blast position, five additional cases were considered for further investigation as they have not been investigated in the existing literature and were found to be worthy of study. The selected locations of the explosive charge included an intermediate zone (between the slab center and free edge), an in-slab region (partly embedded at the free edge), a partial edge (partially outside the slab), an external edge (fully outside the free edge), and an offset position (250 mm beyond the free edge along the central axis). Results indicated a noticeable transition in damage patterns as the detonation point shifted from the slab’s center toward and beyond the free edge. The failure mode changed from a balanced perforation under confined conditions to an asymmetric response near the free edge, dominated by weaker surface coupling but more pronounced tensile cracking and bottom-face perforation. The reinforcement experienced significantly varying tensile and compressive stresses depending on blast position, with the highest tensile demand occurring near free-edge detonations due to intensified local bending and uneven shock reflection. Full article

This paper proposes a hybrid integer optimization method based on the Whale Optimization Algorithm (WOA) for the asymmetric central air conditioning chiller system of a 530-m super high-rise building in Guangzhou. Firstly, a three-hidden-layer multilayer perceptron (MLP) chiller model based on 16,276 sets of measured data and a gradient boosting regression cooling tower model based on 21,369 sets of operating condition data were constructed, achieving high-precision modeling of the energy consumption of all equipment in the chiller system. Secondly, a hybrid encoding strategy of “threshold truncation + continuous relaxation” was proposed to integrate discrete on-off states and continuous operating parameters into WOA, and a three-layer constraint repair mechanism was designed to ensure the physical feasibility of the optimization process and the safe operation of equipment. Verification across three load scenarios—low, medium, and high—showed that the optimized system’s energy efficiency ratio (EER) increased by 15.01%, 12.61%, and 11.86%, respectively, with energy savings of 12.91%, 11.18%, and 10.58%. The annual rolling optimization results showed that the average EER increased from 5.07 to 5.88 (16.1%), with energy savings ranging from 8.59% to 18.92%. Sensitivity analysis indicated that pump quantity is the most influential parameter affecting system energy consumption, with an additional pump reducing it by 1.1%. The optimization method proposed in this paper meets the minute-level real-time scheduling requirements of building automation systems and provides an implementable solution for energy-saving optimization of central air conditioning chiller systems in super high-rise buildings. Full article

Common swifts are extreme aerial specialists that spend most of their lives in flight and use their legs mainly for clinging rather than locomotion. Because functional load is therefore expected to be concentrated on the wing, we hypothesized that the forelimb would exhibit stronger left–right differentiation than the hindlimb. In addition to testing this hypothesis, we used landmark-based geometric morphometric methods to describe humeral and femoral shape in common swifts and to test the effects of sex and body size on bone morphology. The humerus showed clear directional asymmetry: the effect of side explained 13.8% of total shape variance (F = 42.0, p = 0.001), indicating a consistent left–right shift across individuals. The femur also exhibited significant but weaker directional asymmetry, with side accounting for 5.4% of variance (F = 19.3, p = 0.001). In both bones, the individual term explained the largest proportion of variation, whereas residual variance (containing fluctuating asymmetry and measurement error) was moderate (≈27% in the humerus, ≈23% in the femur). Allometric regressions showed a weak but significant size–shape relationship for the humerus and only a marginal effect for the femur, and males and females showed almost complete overlap in the distribution of humeral and femoral shapes. Sex had no detectable effect on humeral or femoral shape or asymmetry, and body size explained only a modest proportion of shape variation in both elements. Overall, our results support the functional expectation: the more intensively used forelimb element is also the more directionally asymmetric one, whereas the femur of this largely aerial bird remains comparatively more symmetrical. Full article

Understanding contact mechanics is essential for optimizing electrical and mechanical interfaces, particularly in systems where surface structuring influences performance. This study investigates the mechanical contact behavior of hot-dip tinned copper surfaces modified via Direct Laser Interference Patterning (DLIP). Asymmetric, line-like microstructures with varying periodicities (2–10 µm) and tilt angles (0°, 15°, 30°) were fabricated on both as-received and aged hot-dip tinned copper substrates. The resulting surfaces were characterized using confocal laser scanning microscopy and subjected to indentation testing under controlled loads. Contact mechanical calculations and finite element simulations were employed to determine critical values for plastic deformation onset and to access the real contact area. Results show that structural periodicity, tilt angle, and material condition significantly affect load-bearing capacity and deformation behavior. Notably, intermediate periodicities (e.g., 7.5 µm) on as-received material at 0° tilt exhibited the highest susceptibility to plastic deformation, while aged samples demonstrated improved mechanical stability due to the harder Cu₆Sn₅ surface layer, which forms directly after coating and grows during aging until it reaches the surface and no residual tin is left. These findings provide valuable insights into the design of structured contact surfaces for electrical applications, highlighting the importance of tailored surface morphology and material selection. Full article

With the in-depth construction of the new power system, the importance of demand-side resources is becoming more and more prominent. The virtual power plant (VPP) has become a powerful means to explore the potential value of distributed resources. However, the differentiated resources between different VPPs are not reasonably deployed, and the problem of realizing the sharing of resources and the distribution of revenues among multi-VPP needs to be urgently solved. A cooperative operation optimization strategy for multi-VPP to participate in the energy and reserve capacity markets is proposed, and the potential risks associated with uncertainty in distributed generators (DGs) output are quantitatively assessed using conditional value-at-risk (CVaR). Firstly, due to the good adjustable performance of electric vehicles (EVs) and thermostatically controlled loads (TCLs), their virtual energy storage (VES) models are established to participate in VPP scheduling. Secondly, based on the asymmetric Nash negotiation theory, a P2P trading method between VPPs in a multi-marketed environment is proposed, which is decomposed into a virtual power plant alliance (VPPA) benefit maximization subproblem and a cooperative revenue distribution subproblem. The alternating direction multiplier method is chosen to solve the model, which protects the privacy of each subject. Simulation results show that the proposed multi-VPP cooperative operation optimization strategy can effectively quantify the uncertainty risk, maximize the alliance benefit, and reasonably allocate the cooperative benefit based on the contribution size of each VPP. Full article