Search Results (466)

In this study, theorems and proofs related to spherical and focal curves are presented in the BCV-Sasakian space. An approximate solution to the differential equation characterizing spherical curves in the BCV-Sasakian manifold ${\mathfrak{M}}^3$ is obtained using the Taylor matrix collocation method. The general equations of canal and tubular surfaces are provided within this geometric framework. Additionally, the curvature properties of the tubular surface constructed around a non-vertex focal curve are computed and analyzed. All of these results are presented for the first time in the literature within the context of the BCV-Sasakian geometry. Thus, this study makes a substantial contribution to the differential geometry of contact metric manifolds by extending classical concepts into a more generalized and complex geometric structure. Full article

Addressing the challenges of bulky, low-efficiency sound-insulation materials at low frequencies, this work proposes an acoustic metamaterial based on curve fractal channels. Each unit cell comprises a concentric circular-ring channel recursively iterated: as the fractal order increases, the channel path length grows exponentially, enabling outstanding sound-insulation performance within a deep-subwavelength thickness. Finite-element and transfer-matrix analyses show that increasing the fractal order from one to three raises the number of bandgaps from three to five and expands total stop-band coverage from 17% to over 40% within a deep-subwavelength thickness. Four-microphone impedance-tube measurements on the third-order sample validate a peak transmission loss of 75 dB at 495 Hz, in excellent agreement with simulations. Compared to conventional zigzag and Hilbert-maze designs, this curve fractal architecture delivers enhanced low-frequency broadband insulation, structural lightweighting, and ease of fabrication, making it a promising solution for noise control in machine rooms, ducting systems, and traffic environments. The method proposed in this paper can be applied to noise reduction of transmission parts for ceramic automation production. Full article

Bamboo scrimber is an environmentally friendly biomass building material with excellent mechanical properties. However, it is susceptible to delamination failure of the transverse fibers under compression, which limits its structural performance. To address this problem, this study utilizes steel tubes to encase bamboo scrimber, forming a novel bamboo scrimber-filled steel tubular column. This configuration enables the steel tube to provide effective lateral restraint to the bamboo material. Axial compression tests were conducted on 18 specimens, including bamboo scrimber columns and bamboo scrimber-filled steel tubular columns, to investigate the effects of steel ratio and loading mode (full-section and core loading) on the axial compression performance. The test results indicate that the external steel tubes significantly enhance the structural load-bearing capacity and deformation capacity. Primary failure modes of the composite columns include shear failure and buckling. The ultimate stress and strain of the structure are positively correlated with the steel ratio; as the steel ratio increases, the ultimate stress of the specimens can increase by up to 19.2%, while the ultimate strain can increase by up to 37.7%. The core-loading specimens exhibited superior load-bearing capacity and deformation ability compared to the full-section-loading specimens. Considering the differences in the curves for full-section and core loading, the steel tube confinement coefficient was introduced, and the predictive models for the ultimate stress and ultimate strain of the bamboo scrimber-filled steel tubular column were developed with accurate prediction. Full article

Due to the frequent occurrence of coarse-grained structures in large hydrogenation tube sheets, their hydrogen resistance and corrosion resistance deteriorate, significantly shortening their service life. Therefore, microstructure evolution must be strictly controlled during the forging process. High-temperature compression tests were simulated using a Gleeble-1500D thermal simulator to investigate the hot deformation behavior of 14Cr1Mo pressure vessel steel under deformation conditions of 1050–1250 °C and strain rates of 0.01–1 s⁻¹. Based on the experimental data, the flow stress curve of 14Cr1Mo steel was obtained, and its thermal deformation behavior was analyzed. Furthermore, the dynamic recrystallization (DRX) kinetic model and grain size model of 14Cr1Mo steel were established. These models were then integrated into the finite element software Forge^® to validate the accuracy of the DRX models. The results showed excellent agreement between the simulated and experimentally measured grain sizes, with a maximum deviation of less than 8%, confirming the high accuracy of the dynamic recrystallization models. These models provide a theoretical basis for finite element simulation and microstructure control in the manufacturing of super-large pressure vessel tube sheet forgings. Full article

This paper primarily investigates the response and failure behavior of 6063-T5 aluminum alloy square tubes with varying outer side lengths under symmetric curvature-controlled cyclic bending in different bending directions. The response is characterized by the moment–curvature relationship and the variation in the outer side length with respect to curvature, whereas failure is characterized by the relationship between the controlled curvature and the number of cycles required to initiate buckling. The outer side lengths studied are 20 mm, 30 mm, 40 mm, and 50 mm, and the bending directions considered are 0°, 22.5°, and 45°. The moment–curvature curves exhibited cyclic hardening, and stable loops were formed for all outer side lengths and bending directions. An increase in the outer side length resulted in a higher peak bending moment, while a greater bending direction led to a slight increase in the peak bending moment. For a fixed bending direction, the curves representing the variation of the outer side length (defined as the change in length divided by the original length) with respect to curvature displayed symmetry, serrated features, and an overall increasing trend as the number of cycles increased, irrespective of the specific outer side length. In addition, increasing either the outer side length or altering the bending direction led to a larger variation in the outer side length. As for the relationship between curvature and the number of cycles required to initiate buckling, the data for each bending direction and each of the four outer side lengths formed distinct straight lines on a double-logarithmic plot. Based on the experimental observations, empirical equations were developed to characterize these relationships. These equations were then used to predict the experimental data and showed excellent agreement with the measured results. Full article

Background: Pneumothorax (PTX) is the most common complication of CT-guided lung biopsies. New technical advances, namely the optimization of needle approach angles within an a priori defined “safe zone,” are intended to reduce this risk. This study evaluates whether PTX incidence and chest tube placement decreased significantly after these technical advances were implemented. Methods: We retrospectively analyzed 118 consecutive patients who had undergone CT-guided lung biopsy between 9 January 2020, and 4 April 2025. The study was divided into three periods of increasingly growing institutional procedural experience: Pre-Knowledge (January 2020–March 2022; n = 45), Partial Knowledge (April–December 2022; n = 18), and Full Knowledge (January 2023–April 2025; n = 55). PTX incidence and chest tube use were compared across periods using chi-square and Fisher’s exact tests, while Kaplan–Meier survival analysis was used to evaluate PTX-free survival over time. Results: Overall PTX incidence significantly declined from 71.1% in the Pre-Knowledge Period to 21.8% in the Full Knowledge Period (p < 0.000001). Rates of chest tube placements also decreased from 17.8% to 9.1%, although this difference was not statistically significant (p = 0.372). Kaplan–Meier analysis showed a statistically significant improvement in PTX-free survival over time (indicating improvement in the timing of complication onset; p = 0.0042). Procedural optimization was also fostered by a large median intrapulmonary needle length and consistent needle angulation within the safe zone. Conclusions: Formal implementation of needle angle optimization and procedural protocol standardization has effectively reduced the frequency and severity of PTX following CT-guided lung biopsies. These results highlight the benefit of continuous education and technique standardization in improving patient safety and clinical outcomes. Full article

This study systematically investigates the axial compression capacity calculation method for 7075-T6 aluminum alloy rectangular hollow section (RHS) members based on the Continuous Strength Method (CSM). Axial compression tests were conducted on nine RHS specimens using a YAW-500 electro-hydraulic servo testing machine, and nonlinear finite element models considering material plasticity and geometric imperfections were established using ABAQUS/CAE. The numerical results showed good agreement with experimental data, verifying the model’s reliability. Parametric analysis was then performed on RHS members, leading to the development of a CSM-based capacity calculation method and a modified curve for predicting the stability reduction factors of square hollow section members. The approach combining this modified curve with Chinese codes is termed the Modified Chinese Code Method. The axial capacities calculated by the CSM-based method, Modified Chinese Code Method, EN 1999-1-1, and AASTM were compared for accuracy evaluation. The conclusions indicate that the proposed modified curve provides more accurate predictions of stability coefficients for square tubes, and the CSM-based method yields more precise capacity predictions than existing international design codes, though it may overestimate the capacity for Class 4 cross-section members and thus requires further refinement. Full article

Belle II is a particle physics experiment working at an high luminosity collider within a hard irradiation environment. The Time-Of-Propagation detector, aimed at the charged particle identification, surrounds the Belle II tracking detector on the barrel part. This detector is composed by 16 modules, each module contains a finely fused silica bar, coupled to microchannel plate photomultiplier tube (MCP-PMT) photo-detectors and readout by high-speed electronics. The MCP-PMT lifetime at the nominal collider luminosity is about one year, this is due to the high photon background degrading the quantum efficiency of the photocathode. An alternative to these MCP-PMTs is multi-pixel photon counters (MPPC), known as silicon photomultipliers (SiPM). The SiPMs, in comparison to MCP-PMTs, have a lower cost, higher photon detection efficiency and are unaffected by the presence of a magnetic field, but also have a higher dark count rate that rapidly increases with the integrated neutron flux. The dark count rate can be mitigated by annealing the damaged devices and/or operating them at low temperatures. We tested SiPMs, with different dimensions and pixel sizes from different producers, to study their time resolution (the main constraint that has to satisfy the photon detector) and to understand their behavior and tolerance to radiation. For these studies we irradiated the devices to radiation up to $5\times {10}^{11}1$ MeV neutrons equivalent (neq) per cm² fluences; we also started studying the effect of annealing on dark count rates. We performed several measurements on these devices, on top of the dark count rate, at different conditions in terms of overvoltage and temperatures. These measurements are: IV-curves, amplitude spectra, time resolution. For the last two measurements we illuminated the devices with a picosecond pulsed laser at very low intensities (with a number of detected photons up to about twenty). We present results mainly on two types of SiPMs. A new SiPM prototype developed in collaboration with FBK with the aim of improving radiation hardness, is expected to be delivered in September 2025. Full article

This study proposes a Tube-based Robust Model Predictive Control (Tube-RMPC) strategy for autonomous vehicle control to address model parameter uncertainties and variations in road–tire adhesion coefficients in complex road scenarios. More specifically, the proposed approach improves the representation of vehicle dynamic behavior by introducing a unified vehicle–tire modeling framework. To facilitate computational tractability and algorithmic implementation, the model is systematically linearized and discretized. Furthermore, the Tube-based Robust Model Predictive Control strategy is developed to improve adaptability to uncertainty in the road surface adhesion coefficient. The Tube-based Robust Model Predictive controller ensures robustness by establishing a robust invariant tube around the nominal trajectory, effectively mitigating road surface variations and enhancing stability. Finally, a co-simulation platform integrating CarSim and Simulink is employed to validate the proposed method’s effectiveness. The experimental results demonstrate that Tube-RMPC improves the path-tracking performance, reducing the maximum tracking error by up to 9.17% on an S-curve and 2.25% in a double lane change, while significantly lowering RMSE and enhancing yaw stability compared to MPC and PID. Full article

Perfusable microvasculature is critical for advancing in vitro tissue models, particularly for neural applications where limited diffusion impairs organoid growth and fails to replicate neurovascular function. This study presents a versatile fabrication platform that integrates mesh-driven design, two-photon lithography (TPL), and modular interfacing to create multi-material, perfusable 3D microvasculatures. Various 2D and 3D capillary paths were test-printed using both polygonal and lattice support strategies. A double-layered capillary scaffold based on the Hilbert curve was used for comparative materials testing. Methods for printing rigid (OrmoComp), moderately stiff hydrogel (polyethylene glycol diacrylate, PEGDA 700), and soft elastomeric (photocurable polydimethylsiloxane, PDMS) materials were developed and evaluated. Cone support structures enabled high-fidelity printing of the softer materials. A compact heat-shrink tubing interface provided leak-free perfusion without bulky fittings. Physiologically relevant flow velocities and Dextran diffusion through the scaffold were successfully demonstrated. Cytocompatibility assays confirmed that all TPL-printed scaffold materials supported human neural stem cell viability. Among peripheral components, lids fabricated via fused deposition modeling designed to hold microfluidic needle adapters exhibited good biocompatibility, while those made using liquid crystal display-based photopolymerization showed significant cytotoxicity despite indirect exposure. Overall, this platform enables creation of multi-material microvascular systems facilitated by TPL technology for complex, 3D neurovascular modeling, blood–brain barrier studies, and integration into vascularized organ-on-chip applications. Full article

Background: Hereditary cancer syndromes such as BRCA1/2 and Lynch syndrome significantly increase the lifetime risk of ovarian, fallopian tube, and endometrial cancers. Risk-reducing salpingo-oophorectomy (RRSO) and hysterectomy are standard preventive strategies. Vaginal natural orifice transluminal endoscopic surgery (vNOTES) has recently emerged as a minimally invasive, scarless alternative that may enhance patient acceptance while maintaining oncologic safety. Objective: This narrative review aims to synthesize the current evidence regarding the role of vNOTES in risk-reducing gynecologic surgery for women with hereditary cancer syndromes, focusing on surgical feasibility, technical considerations, oncologic safety, and patient-reported outcomes. Methods: A structured literature search was conducted in PubMed and Web of Science for studies published between January 2000 and April 2025, using terms related to vNOTES, prophylactic gynecologic surgery, BRCA mutations, and Lynch syndrome. Inclusion criteria focused on studies reporting outcomes of vNOTES in risk-reducing or oncologic contexts. A total of eight studies were included for qualitative synthesis. Results: vNOTES has demonstrated technical feasibility and favorable surgical outcomes in risk-reducing procedures such as RRSO and hysterectomy in BRCA and Lynch syndrome carriers. Comparative studies report lower postoperative pain, faster recovery, and high patient satisfaction, with oncologic standards maintained through specimen containment, peritoneal inspection, and adherence to the SEE-FIM protocol. Limitations include the learning curve and restricted access to the upper abdomen, which may necessitate hybrid approaches in selected cases. Conclusions: vNOTES offers a promising, patient-centered surgical approach for hereditary cancer prevention, combining oncologic safety with enhanced recovery and cosmetic benefits. Further research is needed to standardize protocols, evaluate long-term outcomes, and define its role within broader personalized cancer prevention strategies. Full article

Microbial detection in milk is crucial for food safety and quality, as beneficial and harmful microorganisms can affect consumer health and dairy product integrity. Identifying and quantifying these microorganisms helps prevent contamination and spoilage. The study employs advanced molecular techniques to detect and quantify the genomic DNA for the target hydrolytic enzyme coding genes lipA and aprX based on the multi-align sequence conserved region, specific primer pair, and hydrolysis probes designed using the singleplex qPCR and multiplex qPCR. Cultured isolates and artificially contaminated sterilized ultra-high-temperature (UHT) milk were analyzed for their specificity, cross-reactivity, and sensitivity. The finding indicated that strains with lipA and aprX genes were amplified while the other strains were not amplified. This indicated that the designed primer pairs/probes were very specific to the target gene of interest. The specificity of each design primer pair was checked using SYBR Green qPCR using 16 different isolate strains from the milk sample. The quantification specificity of each strain target gene was deemed to be with a mean Ct value for positive pseudomonas strain > 16.98 ± 1.76 (p < 0.0001), non-pseudomonas positive strain ≥ 27.47 ± 1.25 (p < 0.0001), no Ct for the negative control and molecular grade water. The sensitivity limit of detection (LOD) analyzed based on culture broth and milk sample was >10⁵ and >10⁴ in PCR amplification while it was >10⁴ and >10³ in real-time qPCR, respectively. At the same time, the correlation regression coefficient of the standard curve based on the pure culture cell DNA as the DNA concentration serially diluted (20 ng/µL to 0.0002 ng/µL) was obtained in multiplex without interference and cross-reactivity, yielding R² ≥ 0.9908 slope (−3.2591) and intercepting with a value of 37, where the efficiency reached the level of 95–102% sensitivity reached up to 0.0002 ng/µL concentration of DNA, and sensitivity of microbial load was up to 1.2 × 10² CFU/mL. Therefore, multiplex TaqMan qPCR simultaneous amplification was considered the best method developed for the detection of the lipA and aprX genes in a single tube. This will result in developing future simultaneous (three- to four-gene) detection of spoilage psychrotrophic bacteria in raw milk. Full article

Accurate detection of downhole tubing leakage in gas wells is essential for planning effective repair operations and mitigating safety risks in annulus pressure buildup wells. Current localization methods employ autocorrelation analysis to exploit the time-delay features of acoustic signals traveling through the tubing–casing annulus. This allows non-invasive wellhead detection, avoiding costly tubing retrieval or production shutdowns. However, field data show that multiphase flow noise, overlapping reflected waves, and coupled multi-leakage points in the wellbore frequently introduce multi-peak interference in acoustic autocorrelation curves. Such interference severely compromises the accuracy of time parameter extraction. To resolve this issue, our study experimentally analyzes how leakage pressure differential, aperture size, depth, and multiplicity affect the autocorrelation coefficients of acoustic signals generated by leaks. It compares the effects of different noise reduction parameters on leakage localization accuracy and proposes a characteristic time selection principle for autocorrelation curves, providing a new solution for precise leakage localization under complex downhole conditions. Full article

In this paper, a new type of combined column, square steel tube hybrid steel–basalt fiber reinforced concrete column (BSFCFST), is proposed for the first time, and a new hybrid machine learning model, NRBO-XGBoost, is proposed to predict the axial compressive load capacity of BSFCFST. Eleven specimens were designed and fabricated to investigate the axial mechanical properties of BSFCFST. The variables considered include basalt fiber volume content, steel fiber volume content, steel tube wall thickness and specimen length to slenderness ratio. The characteristics of damage modes, load-displacement curves and load-strain curves of the new combined columns were mainly investigated. The results showed that the hybrid fibers improved the ultimate load carrying capacity of the specimen, and the improvement of the ductility was obvious. On the basis of the experiments, a parametric expansion analysis of several structural parameters of the specimen was carried out by using ABAQUS finite element software, and a combined model NRBO-XGBoost, based on the Newton-Raphson optimization algorithm (NRBO), and the advanced machine learning model XGBoost was proposed for the prediction of the BSFCFST’s ultimate carrying capacity. The combined model NRBO-XGBoost was evaluated by comparing it with several prediction methods. The results show that the prediction accuracy of the NRBO-XGBoost model is significantly higher than that of other prediction methods, with R² = 0.988, which is a good alternative to existing empirical models. Full article

During the construction of concrete-filled steel tubular (CFST) arch bridges, hollow steel tube arch ribs are typically erected using the cantilever method with cable hoisting. In this construction stage, the arch ribs exhibit low out-of-plane stiffness and are thus highly susceptible to wind-induced vibrations, which may lead to cable failure or even collapse of the structure. Despite these critical risks, research on the aerodynamic performance of CFST arch ribs with different cross-sectional forms during cantilever construction remains limited. Most existing studies focus on individual bridge cases rather than generalized aerodynamic behavior. To obtain generalized aerodynamic parameters and buffeting response characteristics applicable to cantilevered CFST arch ribs, this study investigates two common cross-sectional configurations: four-tube trussed and horizontal dumbbell trussed sections. Sectional model wind tunnel tests were conducted to determine the aerodynamic force coefficients and aerodynamic admittance functions (AAFs) of these arch ribs. Comparisons with commonly used empirical AAF formulations (e.g., the Sears function) indicate that these simplified models, or assumptions equating aerodynamic forces with quasi-steady values, are inaccurate for the studied cross-sections. Considering the influence of the curved arch axis on buffeting behavior, a buffeting analysis computational program was developed, incorporating the experimentally derived aerodynamic characteristics. The program was validated against classical theoretical results and practical measurements from an actual bridge project. Using this program, a parametric analysis was conducted to evaluate the effects of equivalent AAF formulations, coherence functions, first-order mode shapes, and the number of structural modes on the buffeting response. The results show that the buffeting response of cantilevered hollow steel arch ribs is predominantly governed by the first-order mode, which can be effectively approximated using a bending-type mode shape expression. Full article