Search Results (3,502)

Space-deployable antennas have development requirements of an ultra-large aperture, high stiffness, and multi-frequency multiplexing. To address the challenge of stiffness characterization in the multi-closed-loop complex systems of deployable mechanisms, this paper proposes a parametric stiffness modeling method and a static stiffness model is established, ranging from components and limbs to the overall mechanism. The motion/force mapping model of the deployable mechanism is obtained using screw theory, and the stiffness mapping from joint space to workspace is achieved via the Jacobian matrix. A comprehensive stiffness model of the deployable mechanism incorporating joint effects is established based on the principle of virtual work and the superposition principle of deformations, and its validity is verified through finite element simulation. Building on this, stiffness characteristics based on structural configuration are investigated, and structural forms with excellent stiffness performance are selected through comprehensive evaluation. Six configurations of the deployable mechanism are derived topologically from this structure, and the optimal configuration is selected based on stiffness performance. The parametric stiffness modeling method proposed in this study can effectively characterize the contribution of each component to the overall system stiffness. It lays a theoretical foundation for establishing a quantitative relationship between stiffness performance and configuration, enabling performance-based configuration optimization and dimensional optimization. Full article

Fe₂O₃-reinforced PMMA nanocomposites were prepared by melt blending using a twin-screw micro-extruder. Fixed Fe₂O₃ loading of 2.5 wt.% was employed, and mixing times of 6 and 12 min were used to obtain nanocomposites with different dispersion characteristics. The structural and morphological properties of the samples were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM), while their thermal degradation behavior was evaluated by differential thermal and thermogravimetric analyses (DTA/TG). The activation energies of thermal degradation were calculated using the Kissinger, Takhor, and Augis–Bennett methods. Increasing the mixing time improved nanoparticle dispersion and reduced agglomeration. The addition of Fe₂O₃ slightly decreased the characteristic degradation temperatures of PMMA, while the activation energy increased for the better-dispersed sample. The results indicate that interfacial interactions and particle dispersion play important roles in the thermal degradation behavior of PMMA/Fe₂O₃ nanocomposites. Full article

Cervical spondylosis is a common cause of spinal cord dysfunction, and anterior cervical discectomy and fusion (ACDF) is widely employed when conservative treatment fails. Conventional implant systems such as the cervical cage with plate (CCP) and zero-profile stand-alone cage (ZPSC) are commonly used to enhance spinal stability and promote fusion, but they are associated with complications including dysphagia and adjacent segment degeneration. To address these limitations, a novel flexible plate cage system (FPCS) has been developed to optimize biomechanical performance while minimizing surgical risk. In this study, a finite element model of the C3–T1 cervical spine was constructed to simulate ACDF at the C5–C6 level using CCP, ZPSC, and FPCS implants. Under standardized loading conditions, von Mises stress was analyzed in the bone, intervertebral disc, endplates, cage, and screws, using the mean of the top 5% stress values to ensure accuracy. All surgical models showed increased stress compared to the intact reference spine. The ZPSC model exhibited the highest stress in the cage and screws, suggesting a more concentrated load path. The CCP model showed a more evenly distributed stress profile, particularly affecting the inferior adjacent segment. The FPCS model demonstrated moderate cage stress, reduced screw stress, and the highest plate stress, indicating a design that effectively redirects mechanical load from the screw-bone interface toward the anterior plate. This may be related to the unique structural configuration of the FPCS, which secures screws horizontally into the anterior vertebral body without penetrating the endplates. These findings suggest that the FPCS may offer a biomechanically favorable alternative to existing ACDF implants. Full article

Background: Implant therapy is a standard of care for long-term tooth replacement. While high survival rates have been reported for implants placed by specialists, data on outcomes achieved by Advanced Education in General Dentistry (AEGD) residents remain limited. Objectives: To evaluate the clinical performance and complication rates of dental implants placed and restored by AEGD residents under faculty supervision, and to identify factors influencing outcomes after at least one year in function. Methods: A retrospective review was conducted for implants placed between April 2012 and December 2021 at the Eastman Institute for Oral Health. Only implants with ≥1-year follow-up were included. Data included demographics, medical history, smoking status, oral hygiene, peri-implant health, and prosthetic outcomes. Logistic regression was used to assess associations between risk factors and complications. Results: Among 262 implants that survived ≥1 year, the complication rate was low: screw loosening occurred in 8.4%, crown issues in 3.4%, abutment or screw fractures in 0.4%, and early peri-implantitis in 11.5%. Examiner satisfaction was high for esthetics (82.8%) and occlusion (85.9%), and over 80% of patients rated their outcomes between 8 and 10 on a 10-point scale. Diabetes and high plaque index were significant predictors of peri-implantitis. Conclusions: Implants placed and restored by AEGD residents under structured faculty supervision achieved low complication frequencies, and strong patient satisfaction comparable to specialist outcomes. Full article

To improve the efficiency and output power of the twin-screw expander used in natural gas pressure energy recovery, a hybrid NGO-SDERIME algorithm is proposed for structural optimization, with the structural parameters of the male and female rotors selected as the optimization design variables. First, the enhanced Rime Ice Optimization (RIME) algorithm is adopted to perform hybrid improvement on the Northern Goshawk Optimization (NGO) algorithm; then, the stability and superiority of the proposed hybrid algorithm are verified by using a suite of benchmark test functions; finally, the algorithm is applied to the structural optimization of the twin-screw expander, followed by numerical simulation and experimental verification. The results indicate that, compared with other existing algorithms, the proposed NGO-SDERIME hybrid algorithm shows excellent convergence and strong optimization performance. After optimization using this algorithm, the output power of the screw expander increases by 5.5%, the high-speed leakage area is significantly reduced, the isentropic efficiency improves from 75.1% to 78.1%, and the average mass flow rate increases from 18.42 t/h to 18.72 t/h. Full article

Most components fail under complex states of stress and for this reason the study of materials failure under these conditions is an important topic. The article presents the experimental study of the failure of a CFRP material, with a 0/90° cross-ply configuration, subjected to both simple loading conditions (tension, compression, and shear) and combined loading (tension–shear), using a modified Arcan testing method. The Arcan device and specimen geometry were redesigned to reduce experimental errors and the dispersion of results. It was found that there are significant differences between the strength values obtained for simple loads performed by the standardized methods and by the Arcan method, respectively. For this reason, it is recommended to use the Arcan method only for mixed loading modes. Specimens with steel tabs were used to reduce both hole ovality during testing and the number of clamping screws to only four. It was found that the experimental results under complex stress states are well described by the Tsai–Hill failure criterion and the failure envelope for the material studied was plotted. Recommendations are provided regarding the appropriate use of the Arcan method in order to obtain precise results for CFRP composites under multiaxial loading. Full article

Carbon-Fiber-Reinforced Polyetheretherketone (CFR-PEEK) instrumentation is increasingly preferred in spinal oncology for its physical properties, minimizing imaging artifacts and facilitating precise postoperative radiotherapy planning and tumor surveillance. However, a significant technical limitation exists: the current unavailability of dedicated CFR-PEEK pedicle screws for the cervical spine. The smallest available implants are designed for thoracic use (minimum diameter 4.5 mm, minimum length 25 mm), posing substantial risks of neurovascular injury when applied to smaller cervical pedicles. We present a technical note/feasibility report illustrated by a single case of robot-assisted placement of thoracic CFR-PEEK screws in the cervical spine for the treatment of a C7 Giant Cell Tumor. Following neoadjuvant therapy with Denosumab, a single-stage, two-step circumferential resection and reconstruction was performed. The anterior step was complicated by an iatrogenic injury to the highly adherent left vertebral artery (VA), which was successfully repaired. Consequently, the posterior step required maximal precision to preserve the sole remaining intact VA on the right side. Given the anatomical mismatch between the 4.5 mm thoracic screws and the narrow cervical pedicles (measuring as narrow as 3.2 mm on the critical right side), robotic navigation (ExcelsiusGPS^®) was utilized to plan and execute safe trajectories. Specifically, on the side of the intact VA, a small, controlled medial cortical violation was planned to avoid lateral vascular compromise. The procedure resulted in rigid, artifact-free stabilization with no immediate neurological sequelae. This single-case experience suggests that robotic guidance may facilitate adaptation of thoracic CFR-PEEK instrumentation to the cervical spine in selected oncologic scenarios; reproducibility, costs, and long-term outcomes remain uncertain. Full article

Background and Objectives: Complicated osteoporotic thoracolumbar fractures represent a major surgical challenge because compromised bone quality predisposes to progressive deformity, neurological deterioration, and fixation failure. This study aimed to evaluate the clinical and radiological outcomes of hybrid stabilization in patients with severe osteoporotic fractures classified as AO Spine-DGOU OF4–OF5. Materials and Methods: This single-center retrospective observational cohort study included 87 consecutively treated patients with complicated osteoporotic thoracolumbar fractures who underwent surgical treatment between 2012 and 2022. Clinical outcomes were assessed using the Visual Analog Scale (VAS) and Oswestry Disability Index (ODI). Radiological outcomes included the regional kyphotic angle (RKA) and interbody fusion graded according to the Bridwell classification. Imaging was reviewed preoperatively, immediately postoperatively, and at follow-up, with 12-month outcomes used for the principal analysis. Additionally, a retrospective comparative analysis was undertaken between the two largest fixation subgroups within the cohort to explore outcome differences across the most representative construct patterns. Results: At 12 months, complete interbody fusion (Bridwell grade I) was achieved in 75.9% of patients. Mean RKA improved from 29.4° ± 14.1° preoperatively to 7.9° ± 8.0° immediately after surgery, with only minimal loss of correction during follow-up. Mean VAS improved from 7.0 ± 1.8 to 2.1 ± 1.2, while mean ODI decreased from 61.3% ± 6.8% to 9.8% ± 1.2% (both p < 0.001). Reoperation for implant-related mechanical failure was required in three patients (3.4%). Conclusions: Hybrid stabilization with cement augmentation was associated with marked improvement in pain, functional disability, and sagittal alignment, as well as a high rate of interbody fusion at 12 months, in patients with complicated osteoporotic thoracolumbar fractures. Given the retrospective observational design, these findings should be interpreted as associations within the treated cohort. Prospective comparative studies are warranted to further validate these results. Full article

This paper investigates the electromagnetic performance of an outer-rotor spoke-type permanent magnet synchronous generator intended for small wind turbine applications below 5 kW. The study focuses on the influence of structural ferromagnetic components on magnetic flux distribution and overall machine performance. The generator was initially designed and optimized using 2D finite element analysis, followed by a comprehensive 3D model to account for axial flux leakage and structural details; particular attention was given to the fastening screws used. Experimental validation on a dedicated laboratory test bench confirms the accuracy of the 3D model, mainly at lower wind speeds. The results highlight the necessity of including structural components in three-dimensional electromagnetic modeling for accurate performance prediction of flux-concentrating wind turbine generators. Full article

Background/Objectives: Accurate pedicle screw placement is critical in spine surgery, as malposition can cause neurological, vascular, or visceral injuries and compromise construct stability. The primary objective of this study was to develop and experimentally validate a dual quantitative framework for assessing pedicle screw placement accuracy, combining (1) coaxiality, a standardized geometric metric of trajectory alignment, and (2) pedicle wall distance (dpw), a novel parameter defined as the minimal distance between the screw axis and the pedicle cortex providing surgeons with direct, millimetric, clinically actionable feedback. A secondary objective was to compare these parameters: dpw, coaxiality, entry point errors and orientation angle errors between senior surgeons and residents to evaluate the influence of surgical experience. We hypothesized that this framework would provide reproducible quantitative measurements, demonstrate strong agreement with established CBCT-based grading systems, and allow meaningful subgroup comparisons by experience level. Methods: Eight operators (four senior surgeons, four residents) performed 240 pedicle screw insertions on synthetic polyurethane lumbar spine models using freehand, CBCT-assisted, and navigation-assisted techniques. Predefined 3D trajectories were compared with actual screw positions digitized with sub-millimetric precision. Errors, coaxiality, and dpw were computed, and dpw was validated against CBCT-based Gertzbein and Heary classifications. Agreement and diagnostic performance metrics (Kappa, sensitivity, specificity) were calculated. Results: Of 236 analyzable screws, coaxiality correlated with entry point errors (ρ = 0.41), target point errors (ρ = 0.85), and orientation angle errors (ρ = 0.48), confirming its robustness as an engineering metric. dpw provided immediate, interpretable feedback and demonstrated near-perfect agreement with CBCT grading (Kappa = 0.86; sensitivity = 0.96; specificity = 0.97), detecting breaches missed by qualitative classifications. Subgroup analyses indicated small but significant differences between senior and junior surgeons for target point errors (p = 0.006), orientation angle errors (p = 0.025), and coaxiality (p = 0.023), whereas entry point errors (p = 0.201) and dpw (p = 0.163) did not differ significantly. Conclusions: This dual-metric framework bridges engineering rigor and intraoperative applicability. Coaxiality supports reproducible research assessment, while dpw enables actionable surgical feedback. The framework allows objective comparison across operators of different experience levels. Together, these metrics offer a standardized, clinically relevant, and quantitative method for evaluating pedicle screw placement, with potential to enhance surgical safety, education, and patient outcomes. Full article

The screw pump is a critical device for elevating downhole petroleum to the surface, and screw pump failure can significantly disrupt the production of oil wells. Due to the complex structure of the screw pump, the same pump fault can cause different changes in the monitoring parameters, and different faults can also cause the same parameter change. In consequence of the complexity, it requires a large amount of labeled data for a diagnosis model to achieve fault diagnosis of a screw pump in practical application. Aiming for this kind of condition, we discovered the dynamic coupling effect between multi-source information through detailed research on the collected data of screw pumps. To fully leverage the information dynamic coupling (IDC) effect, a semi-supervised learning graph attention network (SSL-GAT) fault diagnosis method is proposed. This approach integrates the semi-supervised learning framework and graph attention neural network for the fault diagnosis of a screw pump. The experimental validation of the SSL-GAT method demonstrates its outstanding performance in screw pump fault diagnosis. Full article

Background: Posterior decompression with instrumented fusion (PDF) is a conventional surgical procedure performed in patients with massive ossification of the posterior longitudinal ligament (OPLL); however, it is invasive to the posterior cervical tissues. In this report, we introduce a novel PDF technique, exoscopic minimally invasive open-door laminoplasty with pedicle screw fixation (exLAPPS), to treat cervical OPLL, while minimizing posterior tissue damage. Methods: ExLAPPS was indicated for patients with K-line (−) OPLL or a canal occupying a ratio of ≥50%, allowing decompression from C3 to C7. A small midline incision was used for the navigation reference placement and exoscopic minimally invasive open-door laminoplasty, whereas bilateral lateral incisions were utilized for posterior fixation, including pedicle screw insertion, based on the minimally invasive cervical pedicle screw technique. Results: A total of 7 patients with K-line (-) or a canal occupancy ≥50% underwent exLAPPS for cervical OPLL. The mean operative time was 248 min (range, 165–342 min) and the mean blood loss was 320 mL (range, 50–740 mL). Postoperative imaging demonstrated adequate spinal cord decompression in all patients. A total of 52 pedicle screws were inserted, with a pedicle screw deviation rate of 1.9%. Conclusions: ExLAPPS is a minimally invasive surgical technique designed for posterior decompression and fixation in patients with cervical OPLL. In this preliminary case series, the procedure was successfully performed with acceptable operative time, blood loss, and screw placement accuracy. Although the present study did not include a direct comparison with conventional procedures, these preliminary observations suggest that ExLAPPS is a feasible surgical option for selected patients with cervical OPLL. Full article

Polyethylene terephthalate (PET) plays a pivotal role in the chemical fiber industry, constituting over 50% of fiber consumption. However, the reduction of the recycled fiber-derived viscosity of the PET significantly impacts its spinning performance and restricts its closed-loop recycling to high-value regenerated fibers. To address these limitations, this study explored the viscosity improvement of black and white waste fiber-derived polyester particles through a two-step process involving micro-glycolysis and self-polycondensation. Initially, a continuous micro-glycolysis of fiber-derived PET was carried out in a twin-screw extruder with ethylene glycol (EG), which effectively cleaves the ester bonds in the PET chains, generating oligomers with reactive hydroxyl end groups. Subsequently, these oligomers were repolymerized without purification, and a higher molecular weight regenerated PET with enhanced intrinsic viscosity was obtained with antimony ethylene glycolate (Sb-EG) as a catalyst. The results revealed that the intrinsic viscosity decreased exponentially with increasing EG dosage during glycolysis, reaching approximately 50% of the initial value at 0.2–2 phr EG dosages. Optimal viscosity enhancement was achieved at a polycondensation time of 1–3 h, resulting in improved thermal stability and reduced crystallization temperatures. Importantly, regenerated PET samples with EG dosages of ≤2 phr demonstrated intrinsic viscosities of about 0.70 dL/g, meeting the standard for spin-grade polyester fiber, which is used to produce regenerated polyester fibers. This recycling process is low cost, environmentally friendly, and easy to scale-up, contributing significantly to the development of industrial recycling of waste polyester fabrics. Full article

Background/Objectives: Lumbar interbody fusion (LIF) is widely utilized to treat multilevel degenerative lumbar spine pathologies. This systematic review aimed to comprehensively review lateral and posterior multilevel LIF procedures and their clinical and radiographic outcomes. Methods: Following the PRISMA guidelines, a search of PubMed, Embase, Web of Science, and Cochrane identified eligible studies. Patient demographics, as well as clinical and radiographic outcomes were collected. Risk of bias was assessed using the MINORS criteria, while randomized trials were evaluated using the RoB-2 tool. An extensive subgroup analysis was completed when that was possible. Results: A total of 45 studies were included consisting of 5623 patients. The pooled outcomes indicated that TLIF demonstrated the lowest operative duration (198.7 ± 77.83 min) and LOS (5.09 ± 2.5 days), alongside favorable ODI (33.68 ± 6.43), VAS leg pain (5.39 ± 0.66), and VAS back pain (4.67 ± 0.79) score gains. Comparative evidence found that LLIF and OLIF provided advantageous radiographic improvement to the posterior approaches. Comparative evidence on techniques challenged the use of autogenous bone within PLIF, PEEK over HA/PA66 cages, and found no advantages in unilateral decompression within TLIF. There was minimal clinical difference in evidence assessing MIS (minimally invasive) vs. open-TLIF or unilateral vs. bilateral pedicle screw fixation (PSF). Conclusions: This is the first systematic review of the multilevel LIF literature, revealing that while pooled data favored TLIF, a publication bias was detected, and comparative evidence reported advantages for lateral and oblique approaches. Given the lack of conclusive evidence, robust study designs are needed to guide clinical decision-making for multilevel lumbar pathology. Full article

Exosomes are nanoscale extracellular vesicles that carry disease-associated microRNAs (miRNAs) and represent promising biomarkers for cancer diagnosis. Triple-negative breast cancer (TNBC) lacks well-defined molecular markers, necessitating sensitive and integrable analytical approaches for TNBC-related exosomal miRNAs. In this study, exosomes were isolated from MDA-MB-231 TNBC cells using a paddle screw-based system designed to enhance mass transfer through active rotation, providing a mechanically driven isolation strategy that is compatible with miniaturized and microfluidic platforms. This dynamic isolation process enabled rapid and efficient exosome recovery within a short processing time. Three TNBC-associated miRNAs encapsulated in the isolated exosomes were quantitatively analyzed using polyadenylation tailing (poly(A) tailing) and specific bidirectional extension sequence-based assays combined with reverse transcription quantitative real-time PCR (RT-qPCR). The bidirectional extension (BDE) assay generated highly specific PCR templates, leading to improved amplification specificity and reduced background signals. The RT-qPCR analysis exhibited high sensitivity, wide dynamic range, and good reproducibility for all target miRNAs. Overall, these results demonstrate that the integration of a paddle screw-based exosome isolation module with an extension-based nucleic acid detection strategy provides a scalable and biosensor-compatible analytical framework for profiling TNBC-associated exosomal miRNAs, with potential applications in microfluidic liquid biopsy platforms and exosome-based cancer diagnostics. Full article