Search Results (160)

A modified static characteristic model for the multi-layer foil thrust bearing (MLFTB) is established. In this model, the finite difference method and the thick plate element are implemented, the compressible Reynolds equation is linearized by the Newton–Raphson method, and the evolution law of the static characteristics with the geometric and operational parameters is derived by iterative solution. The results indicate that the bearing capacity could be generally decreased by around 3.15% when considering the slip boundary condition, which should not be neglected. Also, when under the rigorous wedge effect, the pressure peak near the mini clearance exhibits an obvious double peak shape. The bearing capacity can be slightly enhanced by an increase in the tilt angle of the thrust disk. In comparison to data in the literature, the current model shows satisfactory precision for the multi-layer foil thrust bearing. It aims to provide effective predictive means and theoretical reference for MLFTB. Full article

This study aimed to evaluate mandibular fixation techniques using monocortical plates following sagittal split ramus osteotomy in skeletal Class III patients. Ninety-three patients were categorized into three groups based on fixation methods: four-hole miniplate with one proximal and two distal screws (Group 1); four-hole miniplate with four screws (Group 2); sliding plate with two proximal and one distal screws (Group 3). Cone-beam computed tomography scans were obtained at three time points: immediately postoperative (T1), 6 months (T2), and 12 months (T3). The yaw, roll, and pitch rotations of the proximal segment, as well as horizontal and vertical changes of the pogonion, were evaluated. Group 1 exhibited significantly greater counterclockwise rotation of the proximal segments at T2 (p = 0.021) and T3 (p = 0.035) compared to the other groups. Additionally, Group 1 showed significantly smaller anterior and superior displacement of the pogonion at T3 (0.97 ± 2.10 mm, p = 0.009; 0.03 ± 1.62 mm, p = 0.011, respectively). Following surgical wafer removal, intimate occlusal contact is archived and the elimination of premature contacts through postoperative orthodontic treatment contributes to counterclockwise autorotation of the mandible. Therefore, anterior and superior movements of the pogonion are expected if firm fixation between the proximal and distal segments is achieved. Therefore, these findings suggest that a single proximal screw, as seen in a three-screw fixation, may act as a fulcrum, insufficiently resisting postoperative clockwise rotation of the distal segments. Full article

The aerodynamic performance of an aircraft can be enhanced by incorporating wingtip devices, or winglets, which primarily reduce lift-induced drag created by wingtip vortices. This study outlines an optimization procedure for implementing winglets on a Class I fixed-wing mini-UAV to maximize aerodynamic efficiency and performance. After the Conceptual and Preliminary design phases, a baseline UAV was developed without winglets, adhering to specific layout constraints (e.g., wingspan, length). Various winglet designs—plate and blended types with differing heights, cant angles, and sweep angles—were then created and assessed. A Computational Fluid Dynamics (CFD) analysis was conducted to evaluate the flow around both the winglet-free UAV and configurations with each winglet design. The simulations employed Reynolds-Averaged Navier-Stokes (RANS) equations coupled with the Spalart-Allmaras turbulence model, targeting the optimal winglet configuration for enhanced aerodynamic characteristics during cruise. Charts of lift, drag, pitching moment coefficients, and lift-to-drag ratios are presented, alongside flow contours illustrating vortex characteristics for both baseline and optimized configurations. Additionally, dynamic stability analyses examined how winglets impact the UAV’s stability and control. The results demonstrated a significant improvement in aerodynamic coefficients ($C_{Lmax}$, $L/D_{max}$, $C_{La}$, $C_{ma}$), leading to an increase in both range and endurance. Full article

Background/Objectives: Patient-specific osteosynthesis (PSO) plates, in combination with virtual surgical planning (VSP), have significantly improved the accuracy of orthognathic surgery. This study aimed to compare the surgical accuracy of two-plate versus four-plate fixation methods in Le Fort I osteotomies using PSO. Methods: A retrospective cohort study was conducted on 21 patients who underwent maxilla-first bimaxillary surgery at a single centre in 2024. Eight patients received two-plate fixation, while thirteen received four-plate fixation. All surgeries were planned using VSP. Postoperative cone beam computed tomography scans were used to assess the accuracy of maxillary positioning by comparing the planned versus achieved outcomes in terms of translation and rotation. Results: Both fixation methods yielded comparable results in maxillary positioning, with no significant differences observed between the two groups regarding translational or rotational deviations. The two-plate PSO approach demonstrated practical benefits, including reduced material usage and the potential for smaller surgical incisions, without compromising surgical accuracy. Conclusions: Two-plate PSO fixation is a viable alternative to the traditional four-plate method for Le Fort I osteotomies, offering similar accuracy with potential procedural advantages. While these findings support broader clinical adoption, further research is warranted to confirm the results in larger cohorts and to investigate biomechanical considerations. Full article

Background/Objectives: The objective of this study was to analyze the profiles of sphingosine (Sph), sphinganine (SPA), sphingosine-1-phosphate (S1P), and ceramides (C14 Cer, C16 Cer, C18:1 Cer, C18 Cer, C20 Cer, C22 Cer, C24:1 Cer, and C24 Cer), along with caspases (CAS-3, CAS-6, and CAS-9), in serum and in the periosteum of the maxilla and mandible in patients with dentofacial deformities undergoing treatment with titanium fixations (miniplates and miniscrews). Methods: The study group comprised 20 patients who underwent bilateral jaw osteotomy due to dentofacial deformities. The osteotomy segments were stabilized with titanium alloy miniplates and screws. The control group consisted of 20 patients who had not yet received surgical treatment for maxillofacial defects. Results: Sphinganine (SPA) and ceramide C22 (C22 Cer) were the only compounds found to be significantly elevated in the serum of the study group compared to the control group. The concentrations of Sph, SPA, C14 Cer, C16 Cer, C18 1 Cer, C18 Cer, C22 Cer, C24 1 Cer, C24 Cer, and S1P were significantly lower in the maxillary periosteum of patients in the study group compared to those in the control group. The concentration of C20 Cer was significantly higher in the maxillary periosteum of patients in the study group compared to the control group. In contrast, the concentrations of Sph, SPA, C14 Cer, C16 Cer, C18 1 Cer, C22 Cer, C24 1 Cer, and C24 Cer were significantly lower in the mandibular periosteum of the study group compared to the control group. The concentrations of C20 Cer and S1P were significantly elevated in the mandibular periosteum of patients in the study group compared with the control group. The activity of CAS-3 was significantly higher in the mandibular periosteum of patients in the study group compared to those in the control group. Conclusions: Titanium fixations induce local changes in the sphingolipid profile within the periosteum of the maxilla and mandible, while no systemic impact on this metabolism was observed. Full article

The vibration response of a component, particularly the frequency response of the component, can be used in the determination of the loss factor damping, η, due to energy dissipation and the elastic modulus (E). The ASTM E756-04 standard provides the methodology and the guidance for the determination of the loss factor damping and elastic modulus experimentally. This standard specifically calls for the use of a beam with a rectangular cross-section. Also, the theoretical formulation developed there is based on such a beam cross-section. Here, in this paper, the theoretical formulation and numerical simulation for determining the loss factor damping and elastic modulus are a derivation of the methodology used in the ASTM standard and other R&D work, but for a circular plate configuration. The delta change derivation, both theoretically and numerically, is proven to be accurate and validated here. This method is useful in the characterization of materials that have applications in structural vibration, aerospace subcomponents, micro and mini sensory devices, medical devices, and many other areas. Similar to the ASTM standard, the materials could include metals, ceramics, rubbers, plastics, reinforced epoxy matrices, composites, and woods. This paper mainly formulates the technique via numerical and computational methods. It is the intention of the author to also, as a future research agenda, experimentally produce data that can be correlated with this theoretical and numerical methodology. Full article

The aim of the study was to evaluate the effect of titanium implants (Ti6Al4V) on the surrounding tissues by analyzing the concentration of titanium particles, TNF-α, and caspase-3 in patients treated for jaw fractures and dentofacial deformities. The research material consisted of peri-implant tissues: fragments of periosteum adhering to a titanium miniplate and blood serum collected from 42 patients treated for mandibular fractures (Group I), and dentofacial deformities (Group II) who underwent bimaxillary osteotomy. The control group consisted of 24 generally healthy patients before bimaxillary osteotomy. The concentrations of selected cytokines, caspase-3, TNF-α in blood serum, and homogenized tissues, were determined using the immunoenzymatic method (ELISA). The concentration of titanium particles was assessed using a scanning electron microscope equipped with an X-ray microanalyzer. A significant increase in the concentration of titanium, caspase-3, and TNF-α was observed in serum and periosteum in all patients who underwent bone fixation. Increased TNF-α levels indicate an intense immune response, which may lead to the degradation of peri-implant tissues and bone resorption around the miniplates and screws, while an increase in caspase-3 levels suggests that cells surrounding the implants are destroyed in response to inflammatory stress or damage induced by the presence of titanium particles. Full article

Titanium is widely recognized for its biocompatibility and utility in maxillofacial and orthopedic surgery; however, its influence on bone remodeling biomarkers remains underexplored. This study investigates the effects of uncoated titanium plates on both the growth factors and diacylglycerols (DAGs) in the periostea of the maxilla and mandible, as DAG signaling is an essential secondary messenger molecule involved in intracellular signaling connected to various growth factors. The study group comprised 20 patients undergoing bimaxillary osteotomies using miniplates and screws made of Ti6Al4V titanium, from whom bone fixations were removed, while the control group included 20 patients operated on for dentofacial deformities (before the insertion of titanium fixations). Diacylglycerol levels in the serum and periosteum were analyzed using tandem mass spectrometry coupled with ultra-high performance liquid chromatography. Growth factors in the periosteum were measured via ELISA with commercially available assay kits. Our findings demonstrate a significant reduction in growth factors, including IGF-1, PDGF, and FGF-23, alongside decreased total DAG levels, suggesting titanium plate stabilization may modulate bone remodeling dynamics. Notably, while overall DAG levels declined, specific DAG species such as C16:0/16:0 and C18:0/18:0 were elevated, whereas polyunsaturated DAGs showed reductions, indicating selective regulation of lipid signaling pathways. Correlation analyses highlighted complex interactions between growth factors and DAGs, with distinct regional differences observed in the mandibular and maxillary periostea. These alterations may result from chronic titanium exposure, potentially inducing a low-grade immune response or modifying the local biochemical environment. This study emphasizes the need for further research into the long-term effects of titanium implants, particularly their influence on lipid metabolism, growth factor dynamics, and bone healing. Full article

Background: We have applied an anterior locking compression mini plate in addition to a conventional superior locking compression plate for the treatment of wedge or multifragmentary clavicular fractures. Methods: Medical and radiologic data were retrospectively reviewed for patients who underwent surgical fixation with an anterior locking compression mini plate and conventional anatomical locking compression plate in a clavicle fracture of AO/OTA 15.2 B and 15.2 C. The primary outcome was bone union, and the secondary outcome was postoperative complications associated with the procedure. The functional outcomes included the Visual Analog Scale (VAS), University of California at Los Angeles Shoulder Scale (UCLASS), and Constant Shoulder Scale (CSS). Results: Nineteen patients with AO/OTA 15.2 B and 2 C clavicular fractures were followed for an average of 16 months (range: 12–30). The average patient age was 41 (range: 21–76) years, and 17 male and 2 female patients were included. The most common cause of clavicle fractures was sports activity (36.8%). A total of 10 patients had AO/OTA classification 15.2 C, and 9 patients had AO/OTA classification 15.2 B clavicular fractures. Primary fracture union healing was observed in all 19 (100%) patients, and the average time to bone union was 11 weeks (range: 7~21). There was no fixation failure or postoperative infection. The mean VAS, UCLASS, and CSS scores at the final follow-up were 0.6, 33.4, and 65 on a 75-point scale (87 on a 100-point scale), respectively. Conclusions: Dual plating using an anterior mini plate with a superior LCP could be considered as an option to minimize soft-tissue injury in comminuted mid-shaft clavicle fractures. Full article

Objectives: Titanium miniplates and screws are commonly used in the surgical management of dentofacial deformities. Despite the opinion of the biocompatibility of these bone fixations, some patients experience symptoms of chronic inflammation around titanium implants even many years after their application. The aim of this study was to examine the levels of cytokines, chemokines, and growth factors released from the maxilla and mandible periosteum surrounding titanium fixations 11 months after the implantation procedure. Methods: From the study group (n = 20) consisting of patients with maxillofacial defects who underwent bimaxillary osteotomy, fragments of the periosteum of the maxilla and mandible adjacent to the titanium miniplates and screws were taken during routine bone fixation removal procedures. From the control group subjects (n = 20), fragments of healthy maxillary and mandibular periosteum were taken prior to surgical treatment of dentofacial deformities. The examination of cytokines, chemokines, and growth factors levels released from the periosteum of jaws was performed using the Bio-Plex Pro Human Cytokine Screening Panel (48-Plex). Results: The study group was characterized by a significant increase in the concentration of most of the tested-for proinflammatory cytokines/chemokines/growth factors compared to the control group, with greater amounts of inflammatory factors released from the periosteum covering the titanium implants in the mandible than from the periosteal cells surrounding the titanium implants in the maxilla. Conclusions: Prolonged exposure to titanium miniplates and screws leads to a disturbance of immune homeostasis in the periosteal cells of the maxilla and mandible. The data obtained indicate the need to remove fixations after the bone fragments have healed. Full article

The market for microinverters is growing, especially in Europe. Driven by rising electricity prices and an easing in legislation since 2024, the number of mini-photovoltaic energy systems (mini-PVs) being installed is increasing substantially. Indoor and outdoor studies of microinverters have been carried out at Paderborn University since 2014. In the indoor lab, conversion efficiencies as a function of load have been measured with high accuracy and ranked according to Euro and CEC weightings; the latest rankings from 2024 are included in this paper. In the outdoor lab, energy yields have been measured using identical and calibrated crystalline silicon PV modules; until 2020, measurements were carried out using 215 W_p modules. Because of increasing PV module power ratings, 360 W_p modules were used from 2020 until 2024. In 2024, the test modules were upgraded to 410 W_p modules, taking into account the increase from 600 W to 800 W of inverter power limits, which is suitable for simplified operation permission (“plug-in”) in many European countries within a homogenised legislation area for such mini-photovoltaic energy systems or “balcony power plants”. This legislation for simplified operation also covers overpowered mini-plants, although the maximum AC output remains limited to 800 W. Presently, yield assessments are being carried out in the outdoor lab, which will take at least a year to be valid and comparable. Kits consisting of PV modules, inverters, and mounting systems are also being evaluated. Yield rankings sometimes differ from efficiency rankings due to the use of different MPPT algorithms with different MPP approach speeds and accuracies. To accelerate yield assessment, we developed a novel, simple formula to determine energy yield for any module and inverter configuration, including overpowered systems. This is a linear approach, determined by just two coefficients, a and b, which are given for several inverters. To reduce costs, inverters will be integrated into the module frame or the module terminal box in the future. Full article

Background: Minimally invasive plate osteosynthesis (MIPO) for clavicular shaft fracture yields favorable functional outcomes and results in less surgery-related soft tissue injury than other techniques. Anterior chest and shoulder skin numbness, a common complication after open reduction and plate fixation, is related to injury to the supraclavicular nerves. We propose MIPO combined with a mini-open approach without fluoroscopy for nerve preservation to minimize the risk of postoperative numbness compared with traditional open plating without nerve preservation. Methods: A total of 59 patients were retrospectively identified, with a follow-up period of 6 months. Thirty-two patients underwent MIPO with mini-open and nerve preservation technique (MIPO group), and 27 patients underwent traditional open plating without nerve preservation (open group). Constant–Murley shoulder outcome score, operation time, wound length, skin numbness, and number of implant removals were compared between the groups. Results: The MIPO group had significantly lower rates of anterior chest and shoulder skin numbness than the open group (MIPO: 12.5% vs. open: 55.6%; p < 0.001). Operation time was significantly longer in the MIPO group than in the open group (MIPO: 109.38 ± 18.83 vs. open: 81.48 ± 18.85; p < 0.001). Wound length was significantly shorter in the MIPO group than in the open group (MIPO: 4.73 ± 0.79 vs. open: 9.76 ± 1.64; p < 0.001). Both groups had similarly excellent Constant–Murley shoulder scores. There were significantly fewer implant removals in the MIPO group than in the open group (MIPO: 6.3% vs. open: 25.9%; p = 0.036). Neither group experienced any infection, implant failure, or nonunion. Conclusions: Our technique combining MIPO with the mini-open approach and supraclavicular nerve preservation yields a lower incidence of skin numbness than traditional open plating without nerve preservation. Full article

In reconstructive surgery following partial mandibulectomy, the biomechanical integrity of the fibula free flap applied to the remaining mandibular region directly influences the prognosis of the surgery. The purpose of this study is to evaluate the biomechanical integrity of two fixation materials [titanium (Ti) and hydroxyapatite/poly-L-lactide (HA-PLLA)]. In this study, we simulated the mechanical properties of miniplate and screw fixations in two different systems by finite element analysis. A three-dimensional mandibular model was constructed and a fibula free flap and reconstruction surface were designed. The anterior and posterior end of the free flap was positioned with two miniplates and two additional miniplates were applied to the angled area of the fibula. The masticatory loading was applied considering seven principal muscles. The peak von Mises stress (PVMS) distribution, size of fixation deformation, principal stresses on bones, and gap opening size were measured to evaluate the material properties of the fixation. In the evaluation of properties, superior results were observed with both fixation methods immediately after surgery. However, after the formation of callus between bone segments at 2 months, the performance of Ti fixation decreased over time and the differences between the two fixations became minimal by 6 months after surgery. The result of the study implies the positive clinical potential of the HA-PLLA fixation system applied in fibula free flap reconstruction. Full article

(1) Objectives: The purpose of this review was to compare the effects of combining skeletal anchorage and Class II devices, both from an overall perspective and individually for each type of appliance, considering as main outcomes the vertical dimensions and the inclination of the mandibular and maxillary incisors. (2) Materials and Methods: A search without time restrictions was performed up to February 2024 in PubMed, PubMed Central, Scopus, and Medline for randomized controlled trials, as well as prospective and retrospective cohort studies, considering Class II patients treated with and without skeletal anchorage. The effect measure used for the meta-analytic evaluation was the standardized mean difference (SMD). The SMD calculation was obtained by subtracting the mean values of T1–T0 for each individual treatment and then calculating the SMD between the treatments involved. The meta-analysis was performed using the standardized mean difference of the mean difference of the T1–T0 change in the outcome between the different treatments evaluated as the effect size. (3) Results: A total of 1217 documents were initially retrieved. According to the PRISMA protocol, 18 studies comparing different skeletal anchorage protocols (upper/lower miniscrews and miniplates), combined with four appliances (Herbst, Forsus, Carriere Motion, and elastics), were included in the analysis. No significant difference in skeletal divergence was found between groups from an overall point of view (SMD: 0.19 (−0.48 to 0.83) according to the random-effects model). A statistically significant reduction in IMPA° was found in patients treated with temporary anchorage devices (TADs) (SMD of 5.58 (3.40 to 7.75)), except for the elastics group (SMD: 3.76 (−0.91 to 8.43)). The effect on the upper incisors’ inclination appeared to be strictly dependent on the type of anchorage (TADs in one or both of the arches). Some limitations must be considered when interpreting the results: the small number of studies included and the heterogeneity among them are among the limitations, and the temporal disparity among some studies; the ages of the patients were not always comparable; and, finally, the clinical relevance of the effects of TADs is sometimes questionable. (4) Conclusions: The vertical dimension seems not to be significantly affected by skeletal anchorage; instead, the proclination of mandibular incisors is generally reduced when TADs are used. Skeletal anchorage might be useful if lingual tipping of the upper incisors is required; however, it is influenced by the anchorage protocol. Full article

Lithium ion (Li-ion) battery packs have become the most popular option for powering electric vehicles (EVs). However, they have certain drawbacks, such as high temperatures and potential safety concerns as a result of chemical reactions that occur during their charging and discharging processes. These can cause thermal runaway and sudden deterioration, and therefore, efficient thermal management systems are essential to boost battery life span and overall performance. An electrochemical-thermal (ECT) model for Li-ion batteries and a conjugate heat transfer model for three-dimensional (3D) fluid flow and heat transfer are developed using COMSOL Multiphysics^®. These are used within a novel computational fluid dynamics (CFD)-enabled multi-objective optimization approach, which is used to explore the effect of the mini-channel cold plates’ geometrical parameters on key performance metrics (battery maximum temperature ($T_{max}$), pressure drop ($∆P$), and temperature standard deviation ($T_{\sigma }$)). The performance of two machine learning (ML) surrogate methods, radial basis functions (RBFs) and Gaussian process (GP), is compared. The results indicate that the GP ML approach is the most effective. Global minima for the maximum temperature, temperature standard deviation, and pressure drop ($T_{max}$, $T_{\sigma }$, and $∆P$, respectively) are identified using single objective optimization. The third version of the generalized differential evaluation (GDE3) algorithm is then used along with the GP surrogate models to perform multi-objective design optimization (MODO). Pareto fronts are generated to demonstrate the potential trade-offs between $T_{max}$, $T_{\sigma }$, and $∆P$. The obtained optimization results show that the maximum temperature dropped from 36.38 to 35.98 °C, the pressure drop dramatically decreased from 782.82 to 487.16 Pa, and the temperature standard deviation decreased from 2.14 to 2.12 K; the corresponding optimum design parameters are the channel width of 8 mm and the horizontal spacing near the cold plate margin of 5 mm. Full article