Deformation Amplitude Research Articles

Predictive value of enhanced corneal biomechanical parameters for ectasia progression.

To determine whether corneal biomechanical parameters can predict ectasia progression. Retrospective observational study. The baseline corneal biomechanical parameters of 64 eyes of 41 young patients (age, < 25 years at the first visit) who were diagnosed with keratoconus (KC) or suspected KC at Osaka University Hospital and followed up for more than two years were reviewed. Suspected KC was defined as borderline cases with no definitive clinical or topographical abnormalities in both eyes. The eyes were divided into progressed (P) and non-progressed (NP) groups using the ABCD grading system of Scheimpflug-based tomography. The Scheimpflug-based corneal biomechanical parameters evaluated included deformation amplitude ratio within 2mm, integrated radius, Ambrósio relational thickness to the horizontal profile, stiffness parameter at the first applanation, stress-strain index, E-staging, and Corvis Biomechanical Index. The optimized tomographic/biomechanical index (TBIv2), Belin/Ambrósio Enhanced Ectasia Deviation (BAD-D), and inferior-superior axial steepening values from Scheimpflug-based tomography were also evaluated. Twenty-three and 41 eyes were categorized into the P and NP groups, respectively. Logistic regression analysis showed that age, BAD-D, and TBIv2 could predict ectasia progression. The specificity, sensitivity, and area under the receiver operating characteristic curve (AUROC) values for BAD-D combined with age were 0.82, 0.60, and 0.83, respectively, whereas those for TBIv2 combined with age were 0.65, 0.82, and 0.82, respectively. Baseline TBIv2 is a potentially useful predictive marker for ectasia progression in young patients, whereas baseline BAD-D could be used for establishing a definitive diagnosis.

A Comparison of the corneal biomechanical properties in pseudoexfoliation glaucoma, primary open angle glaucoma, and healthy subjects using corvis scheimpflug technology

Aims/Purpose: The purpose of this study was to compare corneal biomechanical properties using Corvis Scheimpflug Technology (ST) among pseudoexfoliation glaucoma (PXG), primary open angle glaucoma (POAG), and healthy controls.Methods: Sixty eyes of 60 patients were enrolled in the study. These include 20 eyes with PXG, 20 eyes with POAG and 20 eyes of normal controls. Corneal biomechanical properties measured by Corvis ST were compared among PXG, POAG, and normal control groups. Corneal biomechanical parameters, which included deformation amplitude (DA) ratio maximum (Max) (2mm), Ambrosio relational thickness (ARTh), Integrated radius, and corneal biomechanical index (CBI), were compared and analyzed after adjusting for intraocular pressure and age.Results: There were no significant differences in age, central corneal thickness, and intraocular pressure among the PXG group, POAG group, and normal control group (p = 0.133, p = 0.797, and p = 0.983, respectively). The DA ratio Max (2mm) value was significantly higher in the PXG group compared to normal control group after adjusting for IOP and age (4.48 ± 0.07 vs. 4.22 ± 0.07, p = 0.026). The Integrated Radius value was significantly higher in the PXG group compared to the POAG group after adjusting for IOP and age (8.42 ± 0.18 vs. 7.85 ± 0.17, p = 0.072).Conclusions: PXG showed significant differences compared to POAG and normal controls in corneal biomechanical properties. Even after adjusting for intraocular pressure and age, the cornea in the PXG group exhibited greater flexibility and deformation compared to the POAG and normal control groups. These results suggest that corneal biomechanical properties may influence intraocular pressure measurement in PXG patients and may be related to optic nerve vulnerability.

Study on Soil Freeze–Thaw and Surface Deformation Patterns in the Qilian Mountains Alpine Permafrost Region Using SBAS-InSAR Technique

The Qilian Mountains, located on the northeastern edge of the Qinghai–Tibet Plateau, are characterized by unique high-altitude and cold-climate terrain, where permafrost and seasonally frozen ground are extensively distributed. In recent years, with global warming and increasing precipitation on the Qinghai–Tibet Plateau, permafrost degradation has become severe, further exacerbating the fragility of the ecological environment. Therefore, timely research on surface deformation and the freeze–thaw patterns of alpine permafrost in the Qilian Mountains is imperative. This study employs Sentinel-1A SAR data and the SBAS-InSAR technique to monitor surface deformation in the alpine permafrost regions of the Qilian Mountains from 2017 to 2023. A method for spatiotemporal interpolation of ascending and descending orbit results is proposed to calculate two-dimensional surface deformation fields further. Moreover, by constructing a dynamic periodic deformation model, the study more accurately summarizes the regular changes in permafrost freeze–thaw and the trends in seasonal deformation amplitudes. The results indicate that the surface deformation time series in both vertical and east–west directions obtained using this method show significant improvements in accuracy over the initial data, allowing for a more precise reflection of the dynamic processes of surface deformation in the study area. Subsidence is predominant in permafrost areas, while uplift mainly occurs in seasonally frozen ground areas near lakes and streams. The average vertical deformation rate is 1.56 mm/a, with seasonal amplitudes reaching 35 mm. Topographical (elevation; slope gradient; aspect) and climatic factors (temperature; soil moisture; precipitation) play key roles in deformation patterns. The deformation of permafrost follows five distinct phases: summer thawing; warm-season stability; frost heave; winter cooling; and spring thawing. This study enhances our understanding of permafrost deformation characteristics in high-latitude and high-altitude regions, providing a reference for preventing geological disasters in the Qinghai–Tibet Plateau area and offering theoretical guidance for regional ecological environmental protection and infrastructure safety.

Study on vibration characteristics of anisotropic vehicle rubber bushings by conformal contact force analysis

For ride comfort and handling performance design of vehicles, anisotropic rubber bushings are used as the connection between lower arms and body frames. The nonlinear vibration performance with the deformation amplitude is advantageous to minimise vibration transmission at low magnitude responses and to reduce deformation at large excitations. During transient deformation, the area under the force-deformation curve serves as an indicator for evaluating vibration reduction and isolation performance. The elastomer geometric variables such as the relative radius between the inner and outer contact surfaces are effective design parameters for controlling bushing dynamic behaviour. This study presents a dynamic model to understand the nonlinear stiffness by the contact theory after addressing the actions between elastomer surfaces. The proposed model was confirmed by the measured dynamics stiffness and damping performance. Their influence on the vehicle ride comfort was investigated.

The effect of lateral tarsal strip surgery on corneal biomechanical parameters measured by Corvis ST

PurposeTo evaluate the effect of lateral tarsal strip (LTS) surgery for involutional ectropion on corneal biomechanical properties measured by the Corvis ST device. MethodsThis prospective clinical study examined 23 patients (mean age 67.7 years) undergoing LTS for involutional ectropion. Corneal biomechanics were evaluated preoperatively and at 1 month postoperatively using the Corvis ST. Deformation amplitude, applanation length, highest concavity measurements, and corneal biomechanical indices were compared before and after LTS. ResultsThe second applanation deformation amplitude was significantly reduced after LTS compared to before (0.471 vs 0.428 mm, p = 0.031) indicating improved corneal stiffness. First applanation deflection length also decreased significantly following surgery (2.342 vs 1.967 mm, p = 0.043) suggesting enhanced corneal stability. Highest concavity deformation parameters were unchanged. Corneal biomechanical index, stiffness parameter, and intraocular pressure compensatory effect showed no significant differences pre- versus post-operatively. ConclusionsLTS surgery leads to measurable improvements in select corneal biomechanical parameters, specifically applanation deformation amplitude and deflection length. This preliminary analysis reveals subtle beneficial impacts on corneal stiffness and stability after surgical correction of ectropion. LTS appears to marginally augment corneal biomechanical properties based on Corvis ST assessment.

Dynamic model and performance assessment of inter-story isolation system with supplement inerter (IISI)

The hybrid control combining the conventional seismic isolation and tuned mass damper inerter is recently gaining popularity for the seismic protective strategy. This paper presents a simplified dynamic model of the inter-story isolation system with a supplement inerter (IISI) for seismic performance assessment. The dynamic characteristics, such as modal frequencies, mode shapes, damping ratios, and participation factors, as well as the seismic response spectrum, were studied considering the importance of the equivalent linear model for seismic design. The vibration characteristic formula of the IISI was derived using a simplified 2-degree-of-freedom (2DOF) model. The influence of the calculated parameters of the model on the vibration characteristics was analyzed. To understand the isolation control mechanism, the response transfer function in the frequency domain was derived, and the effects of model parameters on the deformation amplitude amplification factor of the superstructure and substructure were analyzed. Based on equivalent linear properties, a seismic response prediction formula based on the response spectrum method is provided and verified by time history analysis (THA). The effect of soil-structure interaction (SSI) on the simplified 4-DOF model was also studied. The seismic responses and effectiveness of the IISI were evaluated using a Multi-degree-of-freedom (MDOF) model example. The research results demonstrate that the addition of an inerter changes the vibration characteristics of the traditional isolation system. The supplement inerter is effective in controlling the seismic response of the IISI, and the established analysis method can be used to analyze the seismic response of the IISI by incorporating additional inerter mounted in the isolation layer. The hybrid control strategy shows better effectiveness in reducing displacement in the isolation layer.

Process and mechanism analysis of typical permafrost area surface deformation at two sites along the Qinghai-Tibet highway based on long-term leveling observation

Surface deformation indicates permafrost changes and multi-year surveys can reflect its characteristics and causes. In this study, surface deformations in Wudaoliang (WDL) and Xidatan (XDT) were determined based on long-term leveling measurements, hydrothermal data, precipitation and soil sampling. In-situ observations can be used to study the influence of hydrothermal changes in the active layer on the surface. The amplitude and onset date of seasonal deformation are different due to the soil moisture (SM) and soil texture in the two permafrost regions. High SM and fine-grained soils can cause significant seasonal surface deformation. A good correlation existed between the freeze-thaw front migration rate and deformation in the active layer with a uniform distribution of SM. The inter-annual subsidence rate in the WDL was higher than in the XDT, owing to the different rates of ground ice thawing near the permafrost table. The long-term subsidence rate positively correlates with the increased seasonal deformation amplitude, especially in fine-grained soils.

Multi-level stiffness property and isolating-based design of high damping rubber bearings

This study presents the development and analysis of high damping rubber bearings (HDRBs) with enhanced stiffness properties to improve seismic isolation performance. The proposed HDRBs exhibit displacement-dependent nonlinear stiffness and significant damping effects, especially under large deformations caused by various seismic events. A deformation history integral model, calibrated with experimental data, is employed to accurately simulate the mechanical behavior and stiffness-damping characteristics of the HDRBs. The numerical simulations are validated through experimental tests, providing a solid basis for parameter design and performance assessment. The results show that the equivalent stiffness coefficient of the HDRBs increases with deformation amplitude, effectively limiting extreme deformations. Parametric analyses and case studies across a wide range of earthquake scenarios demonstrate that the enhanced stiffness and high damping effects of HDRBs significantly improve seismic isolation efficiency while controlling isolation layer displacement. The performance-based design methodology developed in this research effectively limits bearing deformation, thereby preventing potential superstructure failures. Moreover, the adaptive characteristics of the HDRBs allow for the adjustment of deformation levels according to seismic intensity, ensuring the structural safety of buildings under varying earthquake conditions.

Aeroelastic Effects in Supersonic Shock-Turbulent Boundary Layer Interaction over Flexible Panels

The dynamic coupling between a Mach 1.94 shock wave/turbulent boundary layer interaction (SBLI) and a flexible panel is investigated. High-order numerical simulations are performed for distinctly different dynamic panel motions and rigid snapshots of their maximum deflected shape. They are compared with a baseline interaction over a rigid planar wall. The panel’s dynamic surface motions were obtained from the Air Force Research Laboratory (AFRL) wind tunnel experiments. The primary aim of the study was to determine whether there were any differences in the flow pressure loading on the compliant panel due to the various rigid and dynamic deformations considered. The results show that the examined panel deformations increase the SBLI size near the panel midpoint, where the deformation amplitude tends to be the largest. Relative to the rigid planar case, the examined surface deformations cause the mean-flow high-pressure surface loading caused by the impinging shock wave to shift downstream along the compliant panel midspan, albeit by a small amount. The spectrogram of the dynamic deformation and the flow surface pressure response suggests that the two are strongly coupled at the dominant (primary) mode but less so at the secondary modes. Although the primary mode frequencies overlap, they do not exactly match, with the pressure response frequency always being slightly higher in all three cases. The rigid deformations did not enhance the pressure power content at the SBLI. However, pre-SBLI and near the panel leading edge, the pressure power spectrum weakly increased throughout the resolved frequency range and overlapped with the onset of the amplification found in the dynamic deformation cases. Post-SBLI, the rigid deformations cause a weak enhancement at frequencies below 1 kHz, which closely match the dominant and secondary pressure response frequencies obtained in the dynamic cases.

Quantitative Evaluation of Deformation in High-Speed Magnetic Flux Leakage Signals for Weld Defects in Oil and Gas Pipelines

Complex multiphase flow in oil and gas pipelines raises safety risks. Magnetic flux leakage (MFL) detection effectively identifies pipeline defects. However, the high-speed movement of MFL inspection tools induces motion-induced eddy currents (MIECs), complicating defect recognition and quantification. Most prior research has primarily focused on rectangular defects, leaving a gap in understanding the impact of MIECs on weld defects. This paper proposes the amplitude and shape deformation coefficients to analyze the influence of velocity on various weld defects, including internal reinforcement, lack of penetration, crack, external corrosion, internal corrosion, porosity, and lack of fusion. Utilizing these coefficients, this study examines the influence of the defect size and magnetizer configuration on these velocity-induced effects. The results show that the shape deformation coefficients range from 2.75 to 3.57 for Bx and from −0.13 to −0.3 for By, indicating a significant change in the MFL signal shape at 10 m/s compared to 0 m/s. The amplitude deformation coefficients for lack of penetration, internal corrosion, and porosity range from −0.01 to 0.1 for Bx, and from 0.86 to 0.98 for By, suggesting a decrease in peak-to-peak values. In contrast, other defects exhibit an increase in peak-to-peak values, indicating that the velocity effect may enhance the MFL signal. Also, the defect size and magnetizer configuration can affect the velocity effect on signals. These findings provide essential guidance for quantifying defect sizes and a solid foundation for designing more effective magnetization devices.

A Case Study on the Possibility of Extending the Service Life of the Demining Machine Belt.

The operational practice of the design of the Bozena 5 demining machine has shown that its belts are the critical component that fundamentally affects the functionality of the entire machine. This article is a practical continuation and extension of the previous research results from the point of view of materials (research of the uniaxial fatigue life in bending and torsion), calculation (creation of the necessary mathematical, analytical and numerical models for the research) and construction (i.e., patented design of the belt tensioning of this machine). All these actions are aimed at a single objective-to achieve a condition that guarantees a sufficient service life without malfunctions, since repairing these machines in the field is often impossible. Therefore, this study examined the fatigue life of welded joints (uniaxial bending and torsion) of S960 QL and S500MC steels welded by MAG technology. Subsequently, the data were compared with previous results (electron and laser welds) and the influence of each type of weld on the fatigue life relative to the base material was discussed. It was found that conventional MAG technology had a more significant negative impact on the fatigue life of the base material than non-conventional technologies. This trend was particularly true for the bending stress. At the same time, the bending stress was identified by the FEM analysis as the dominant load on the belt. The maximum stress in the belt link under the considered boundary conditions was approximately 240 MPa (in bending). This stress corresponded to the continuous fatigue life (more than 107 cycles) for both base materials tested (S960QL, S500MC). In the whole studied spectrum of controlled deformation amplitudes (Manson-Coffin), the life of MAG welds was lower in comparison with the base material and with welds made by unconventional technologies. All the activities carried out so far (research on microstructure, hardness, strength, residual stresses, tribological properties and fatigue life) have shown that the original belt design (S500MC) using MAG technology has significant deficiencies in the state of optimal life. It is expected that the proposed material change (use of S960QL instead of S500MC) and work with advanced technologies will bring this state significantly closer.

The visual outcomes and corneal biomechanical properties after PRK and SMILE in low to moderate myopia.

To compare the corneal biomechanical parameters, visual outcome, and epithelial remodeling after small-incision lenticule extraction (SMILE) and photorefractive keratectomy (PRK) for low to moderate myopia. Prospective, interventional, randomized, comparative study. Eighty eyes of 40 patients undergoing bilateral SMILE or PRK for low to moderate myopia (<-5 D SE) were included. They were divided into two groups based on the planned refractive surgery. Visual acuity, corneal biomechanics using Corvis-ST, epithelial mapping via anterior segment optical coherence tomography, and higher-order aberrations were recorded both preoperatively and postoperatively at 6 months and compared. At 6 months follow-up, the corrected distance visual acuity as well as the postoperative spherical equivalent of both the groups were comparable (P = 0.13 and P = 0.32, respectively). The biomechanical parameters like deformation amplitude ratio (P < 0.01), inverse concave radius (P = 0.006), integrated ratio (P < 0.01), stress-strain index (P < 0.01), Ambrosio's relational thickness (ArTH) (P < 0.01), and corneal biomechanical index-laser vision correction (P = 0.02) were altered more in the SMILE group than in the PRK group, while the biomechanically corrected intraocular pressure (P = 0.16) was comparable. Epithelial remodeling (P = 0.59), higher-order aberrations (P = 0.53), and stromal keratocyte loss (P = 0.16) in both the groups were comparable. Both SMILE and PRK are comparably effective procedures for correction of low to moderate myopia in terms of visual outcomes; however, the corneal biomechanical stability in PRK is superior than that in SMILE.

Diagnostic models for differentiating fatty liver disease of alcohol and non-alcoholic genesis

Introduction. Fatty liver disease is the largest contributor to the burden of chronic liver disease worldwide. Current approaches do not allow sufficient differentiation between alcoholic and non-alcoholic etiology of the process.Aim. Create diagnostic panels including electrical and viscoelastic parameters of erythrocytes to differentiate fatty liver disease of alcoholic and non-alcoholic genesis.Materials and methods. The study included 38 men (47.5 ± 2.9 years) with NAFLD; 31 men with alcoholic fatty liver disease (AFLD) (45.1 ± 3.1 years) according to ultrasound of the abdominal organs, the degree of fibrosis did not exceed F1 (FibroScan® 502). Electrical and viscoelastic parameters of erythrocytes were studied by dielectrophoresis using an electro-optical cell detection system. To determine the parameters of erythrocytes – biomarkers for distinguishing between AFLD and NAFLD, a system of machine learning methods – Random Forest was used.Results. Electrical, viscoelastic parameters of erythrocytes, which are biomarkers for distinguishing between AFLD and NAFLD, were established: cell membrane capacity (p = 1.21E-11), the degree of change in the deformation amplitude at a frequency of 5 x 105 Hz (p = 2.38E-08), cell polarizability at a frequency of 106 Hz (p = 9.38E-08), the speed of erythrocyte movement to the electrodes (p = 4.32E-06), the magnitude of the dipole moment (p = 1.66E-05), relative polarizability (p = 2.35E-05), the index of erythrocyte destruction at a frequency of 5 x 105 Hz (p = 0.016), the position of the crossover frequency (p = 2.13E- 06). The diagnostic model, including five parameters – the position of the crossover frequency, cell polarizability at a frequency of 106 Hz, cell electrical conductivity, membrane capacity, the degree of change in the deformation amplitude at a frequency of 5 x 105 Hz, provided the highest diagnostic accuracy with an AUC of 0.975, a sensitivity of 96.3%, and a specificity of 91.8% in differentiating between AFLD and NAFLD.Conclusion. Thus, systematic exposure to alcohol modifies the structure of erythrocyte membranes, leading to a decrease in the surface charge, the barrier function of membranes, reducing the resistance of cells, their ability to deform, which determines the key role of the identified electrical, viscoelastic parameters of erythrocytes in differentiating between AFLD and NAFLD.

Heat transfer-deformation characteristics and fracture damage analysis during LN2 freeze-thaw process in different rank coals

Exploring the heat transfer and deformation characteristics of coal bodies of different coal ranks during the freeze-thaw process is of significant importance for analyzing the fracture mechanism under the effect of liquid nitrogen (LN2). This experiment targets lignite, bituminite, and anthracite under both saturated and dry conditions. A real-time temperature-strain monitoring system was employed to observe the heat transfer and deformation characteristics of coal samples with different ranks throughout the freeze-thaw cycle. Additionally, a nuclear magnetic resonance system was utilized to examine the characteristics of pore damage before and after fracturing. The findings reveal: (1) During the freeze-thaw process, the absolute value of the temperature evolution rate for dry coal samples shows a negative correlation with coal rank, indicating a close link between temperature diffusion and intrinsic coal properties like oxygen content and porosity. (2) For saturated coal samples, the absolute value of the temperature change rate during freezing decreases as the coal rank increases, with the opposite trend observed during thawing. The phase change effect of water in fractures during freezing can enhance internal temperature diffusion in the coal body, while it acts as an inhibitor during thawing. (3) Based on the trend of strain fluctuations, the coal body deformation process during the freeze-thaw cycle can be segmented into seven stages, summarizing the general mechanisms of deformation failure. (4) Under saturated conditions, the amplitude of elastic deformation for each sample is negatively correlated with coal rank, with the sequence for dry coal samples being bituminite > anthracite > lignite. (5) The formation of a sealed space at the beginning of freezing is identified as a necessary condition for deformation during the freeze-thaw process, with the formation and strength of the sealed space depending on the temperature diffusion rate, moisture content, and inherent properties of the coal sample.

Biomechanical corneal effects of LASIK Xtra compared with conventional FS-LASIK in high myopic eyes.

To investigate the in vivo corneal biomechanical response to FS-LASIK combined with accelerated corneal crosslinking (LASIK Xtra) compared with conventional FS-LASIK (convLASIK) in highly myopic eyes. Department of Ophthalmology, Goethe-University, Frankfurt am Main, Germany. Prospective, randomized fellow eye-controlled clinical trial. Patients who received treatment with LASIK Xtra (30mW/cm 2 , 90 seconds with continuous UV-A) in 1 eye and convLASIK in the other eye were enrolled. Both eyes were subjected preoperatively and 12 months postoperatively to a Corvis ST examination. The stiffness parameter at first applanation (SP-A1), integrated inverse radius (IIR), deformation amplitude (DA), deformation amplitude 2 mm away from apex, and the apical deformation (DARatio2mm) were evaluated. The study included 38 high myopic eyes (-7.34 ± 1.02 diopters) of 19 patients. The results of the corneal biomechanical measurement showed a significant reduction in overall corneal stiffness with a significant decrease in postoperative SP-A1 and increase in IIR, DA, and DARatio2mm ( P < .001). In a direct comparison, there was no evidence of an increase in corneal stiffness in the LASIK Xtra group compared with the convLASIK group 12 months postoperatively. No statistically significant difference was detected in any of the 4 biomechanical parameters ( P > .05). The corneal biomechanical response to convLASIK and LASIK Xtra did not vary significantly. With a similar corneal thickness loss, there was no significant difference in the 4 biomechanical metrics between the convLASIK and LASIK Xtra groups. Thus, LASIK Xtra appeared not to have a protective corneal stiffening effect compared with convLASIK 12 months postoperatively.

Evaluation of corneal biomechanical changes in moderate myopia after different techniques of corneal refractive surgeries

Background The most prevalent refractive error, which accounts for between 15 and 49% of cases worldwide, is myopia. Refractive surgery can fix refractive problems and lessen reliance on glasses or contact lenses. Aim This study aims to assess corneal biomechanical alterations following photorefractive keratectomy (PRK) and femtosecond laser small incision lenticule extraction (F-SMILE) in moderate myopic patients using CORVIS-ST (CST). Patients and methods This prospective, comparative, nonrandomized study was conducted on 40 patients’ eyes. with moderate myopia in a private center from January 2020 to December 2020, these eyes were subdivided into two groups: (a) The first group included 20 eyes that will receive PRK (b) The second group included 20 eyes that will receive F-SMILE. All participants will undergo operative (History taking, and examinations), preoperative (PRK, and F-SMILE), and postoperative (medications and Follow-up examinations) evaluations. Results Significant differences existed among the two groups in postoperative follow-up after 1 month and 6 months regarding deformation amplitude, radius, corvis biomechanical index, and intraocular pressure corrected biomechanically but There were insignificant differences among the two groups in terms of SPA in the same periods postoperatively. Conclusion Laser refractive surgery has a major impact on corneal biomechanical properties, as evidenced by significant changes in Corvis ST ocular biomechanical measures following PRK and F-SMILE procedures in myopic patients. The alterations resulting from F-SMILE are more substantial compared with PRK.

The mechanism of aerodynamic performance enhancement of flapping wings with spanwise active deformation

The single stiffness makes the micro-air vehicles (MAVs) only to show excellent flight performance in a specific flow field environment. The MAVs should have the ability to actively deform to adapt to different application scenarios. This study investigates the effects of spanwise active deformation amplitude (ψmax), phase difference (φP), and Strouhal number (St) on the aerodynamic loads and vortex of a wing through numerical simulations. Under the condition of Re= 1000, numerical simulations were conducted on a rectangular wing with an aspect ratio of 4 during the flapping process. The study reveals that moderate spanwise deformation can increase the thrust of the wing and improve propulsion efficiency (ηP). Within the study's scope, the thrust coefficient increases monotonically and linearly with the deformation, but the propulsion efficiency improves only within a limited parameter range. By observing the vortex under different spanwise deformations and monitoring the forces at different positions of the wing, it was found that active deformation can enhance the strength of the leading-edge vortex (LEV) and the wingtip vortex (TV), thereby enhancing the generation of thrust. The results also indicate that the enhancement of LEV is achieved through the coupling between LEV and secondary vortex. At different Strouhal numbers, improvements in ηP can only be achieved through the combined effects of increased vortex strength and optimal vortex residence time. Additionally, it was observed that at lower St, TV can switch from contributing thrust to causing drag.

ЗАРЯДТАЛҒАН ТАМШЫНЫҢ ОРНЫҚСЫЗДЫҚ УАҚЫТЫНА ТҰТҚЫРЛЫҚТЫҢ ӘСЕРІН ТЕОРИЯЛЫҚ ЗЕРТТЕУ

A nonlinear integral equation describing the time-dependent change of viscosity during spherical deformation of an unstable droplet with specific charge was obtained and its solution was determined. Since the considered phenomenon is nonlinear, it was shown that the characteristic time of instability is determined by the time of ten times increase of the amplitude of the virtual spherical deformation of the unstable droplet from the initial negligible value.

Hydrodynamic Characteristics of Preloading Spiral Case and Concrete in Turbine Mode with Emphasis on Preloading Clearance

A pump-turbine may generate high-amplitude hydraulic excitations during operation, wherein the flow-induced response of the spiral case and concrete is a key factor affecting the stable and safe operation of the unit. The preloading spiral case can enhance the combined bearing capacity of the entire structure, yet there is still limited research on the impact of the preloading pressure on the hydrodynamic response. In this study, the pressure fluctuation characteristics and dynamic behaviors of preloading a steel spiral case and concrete under different preloading pressures at rated operating conditions are analyzed based on fluid–structure interaction theory and contact model. The results show that the dominant frequency of pressure fluctuations in the spiral case is 15 fn, which is influenced by the rotor–stator interaction with a runner rotation of short and long blades. Under preloading pressures of 0.5, 0.7, and 1 times the maximum static head, higher preloading pressures reduce the contact regions, leading to uneven deformation and stress distributions with a near-positive linear correlation. The maximum deformation of the PSSC can reach 2.6 mm, and the stress is within the allowable range. The preloading pressure has little effect on the dominant frequency of the dynamic behaviors in the spiral case (15 fn), but both the maximum and amplitudes of deformation and stress increase with higher preloading pressure. The high-amplitude regions of deformation and stress along the axial direction are located near the nose vane, with maximum values of 0.003 mm and 0.082 MPa, respectively. The contact of concrete is at risk of stress concentrations and cracking under high preloading pressure. The results can provide references for optimizing the structural design and the selection of preloading pressure, which improves operation reliability.

Gaussian model of fluctuating membrane and its scattering properties.

A mathematical model is developed to jointly analyze elastic and inelastic scattering data of fluctuating membranes within a single theoretical framework. The model builds on a nonhomogeneously clipped time-dependent Gaussian random field. This specific approach provides one with general analytical expressions for the intermediate scattering function for any number of sublayers in the membrane and arbitrary contrasts. The model is illustrated with the analysis of small-angle x-ray and neutron scattering as well as with neutron spin-echo data measured on unilamellar vesicles prepared from phospholipids extracted from porcine brain tissues. The parameters fitted on the entire data set are the lengths of the chain and the head of the molecules that make up the membrane, the amplitude and lateral sizes of the bending deformations, the thickness fluctuation, and a single parameter characterizing the dynamics.