Search Results (30)

Background/Objectives: Posterior pelvic ring fractures are severe injuries requiring surgical stabilization, often through sacroiliac (SI) screw fixation. However, improper screw placement poses risks of neurovascular injury and implant failure. Defining a precise safe zone for screw placement is crucial to improving surgical accuracy and reducing complications. Methods: A computational study was conducted using a CT scan of a 75-year-old male patient to establish a safe zone for SI screw placement. Manual segmentation and 3D modeling techniques were used to analyze bone density distribution. A 2D lateral projection of the sacrum was generated to identify high-density regions optimal for screw placement. While the general principle of targeting areas of higher bone density for screw insertion is well established, this study introduces a novel computational method to define and visualize such a safe zone. The resulting region, termed the Ramadanov–Zabler Safe Zone, was delineated based on this analysis to ensure maximal intraosseous fixation with minimal risk of cortical breaches. Results: A high-resolution 3D model of the sacral region was successfully generated. Standard thresholding methods for segmentation proved ineffective due to low bone density, necessitating a freehand approach. The derived 2D projection revealed regions of higher bone density, which were defined as the Ramadanov-Zabler Safe Zone for screw insertion. This zone correlates with areas providing the best structural integrity, thereby reducing risks associated with screw misplacement. Additionally, intraoperative and postoperative imaging from a representative case is included to illustrate the translational feasibility of the proposed technique. Conclusions: The Ramadanov–Zabler Safe Zone offers a reproducible, CT-based computational approach to guide for SI screw placement, enhancing surgical precision and patient safety. This CT-based computational approach provides a standardized reference for preoperative planning, minimizing neurovascular complications and improving surgical outcomes. This pilot technique is supported by preliminary clinical imaging that demonstrates feasibility for intraoperative application. Further validation across diverse patient populations is recommended to confirm its clinical applicability. Full article

(1) Background: The incidence of fragility fractures of the pelvis (FFP) has increased significantly over the past decades. Unilateral non-displaced fractures, defined as FFP II, are the most common type of fracture. When conservative treatment fails, surgical treatment is indicated. We hypothesize that the use of bilateral SI screws (BSIs) or a transsacral screw (TSI) is superior compared to a unilateral screw (USI) because of a significant reduction in the risk of adjacent fractures and a reduction in fracture progression. (2) Methods: A finite element model of a female pelvic ring was constructed. The ligaments were simulated as tension springs. The load was applied through the sacrum with the pelvis fixed to both acetabula. An FFP IIc was simulated and fixed with either a USI or BSI or TSI. The models were analyzed for a quantitative statement of stress and fracture dislocation. (3) Results: The BSI and TSI resulted in less dislocation compared to the USI. The stress distribution on both sides of the sacrum was favorable in the BSI and TSI groups. The BSI resulted in a higher rotational stability compared to the TSI. (4) Conclusions: The use of either a BSI or TSI for fixation of unilateral FFP is biomechanically favorable compared to the use of a USI. In addition, the use of a BSI or TSI reduces the stress on the contralateral uninjured side of the sacrum. This may reduce the risk of an adjacent fracture or fracture progression. Full article

(1) Background: Demographic changes over the past decade have had a significant impact on pelvic ring fractures. They have increased dramatically in the orthogeriatric population. Surgeons are faced with implant fixation issues in the treatment of these fragility fractures. This study compares two innovative implants for stabilizing the iliosacral joint in a biomechanical setting. (2) Methods: An iliosacral screw with a preassembled plate allowing the placement of an additional short, angular stable screw in the ilium and a triangular fixation system consisting of a fenestrated ilium screw and an iliosacral screw quasi-statically inserted through the “fenestra” were instrumented in osteoporotic artificial bone models with a simulated Denis zone 1 fracture. Biomechanical testing was performed on a servo-hydraulic testing machine using increasing, synchronous axial and torsional sinusoidal cyclic loading to failure. (3) Results: The SI-Plate and TriFix showed comparable stiffness values. The values for fracture gap angle and screw tip cutout were significantly lower for the TriFix compared to the SI-Plate. In addition, the number of cycles to failure was significantly higher for the TriFix. (4) Conclusions: Implant anchorage and primary stability can be improved in iliosacral instability using the triangular stabilization system. Full article

This research work highlights the tribomechanical investigations of using a low loading fraction of two ceramics combinations, Alumina (Al₂O₃) and Silicon Carbide (SiC) as reinforcement for Low-density Polyethylene (LDPE) matrix. The hybrid additives with different weight percentages (0.1 + 0.1, 0.25 + 0.25 and 0.5 + 0.5 wt%) were mixed with LDPE matrix and the degree of homogeneity was controlled using double-screw extruder prior to fabricating the composite samples via the injection molding machine. The nanoparticles fillers were characterized by field emission scanning electron microscope (FESEM), EDX and particle size analyzer to check its morphology, composition and size distribution. Thermogravimetric analyzer (TGA) and melting flow index (MFI) were performed for the fabricated nanocomposites samples. The mechanical properties of the nanocomposite were evaluated by performing tensile test, bending test and Shore-D hardness test, while the tribological performance was investigated using a ball on desk apparatus under different applied loads and sliding times. Moreover, in order to confirm the load-carrying capability of the composite, contact stresses was measured via finite element model using ANSYS software. The results show that the incorporation of low fraction hybrid ceramic nanoparticles can contributed positively in the tribological and mechanical properties. Based on the experimental results, the maximum improvement in the tensile strength was 5.38%, and 8.15% for hardness LDPE with 0.5 Al₂O₃ and 0.5 SiC, while the lowest coefficient of friction was noticed under normal load of 10 N, which was approximately 12.5% for the same composition. The novel approach of incorporating low fraction hybrid ceramic nanoparticles as reinforcement for LDPE matrix is investigated, highlighting their positive contributions to the tribological and mechanical properties of the resulting nanocomposites. Full article

Background and purpose: Cannulated screws are standard implants for percutaneous fixa-tion of posterior pelvis ring injuries. The choice of whether to use these screws in combination with a washer is still undecided. The aim of this study was to evaluate the biomechanical competence of S1-S2 sacroiliac (SI) screw fixation with and without using a washer across three different screw designs. Material and Methods: Twenty-four composite pelvises were used and an SI joint injury type APC III according to the Young and Burgess classification was simulated. Fixation of the posterior pelvis ring was performed using either partially threaded short screws, fully threaded short screws, or fully threaded long transsacral screws. Biomechanical testing was performed under progressively increasing cyclic loading until failure, with monitoring of the intersegmental and bone-implant movements via motion tracking. Results: The number of cycles to failure and the corresponding load at failure (N) were significantly higher for the fully threaded short screws with a washer (3972 ± 600/398.6 ± 30.0) versus its counterpart without a washer (2993 ± 527/349.7 ± 26.4), p = 0.026. In contrast, these two parameters did not reveal any significant differences when comparing fixations with and without a washer using either partially threaded short of fully threaded long transsacral screws, p ≥ 0.359. Conclusions: From a biomechanical perspective, a washer could be optional when using partially threaded short or fully threaded long transsacral S1-S2 screws for treatment of posterior pelvis ring injuries in young trauma patients. Yet, the omission of the washer in fully threaded short screws could lead to a significant diminished biomechanical stability. Full article

Helical magnets are emerging as a novel class of materials for spintronics and sensor applications; however, research on their charge- and spin-transport properties in a thin film form is less explored. Herein, we report the temperature and magnetic field-dependent charge transport properties of a highly crystalline MnP nanorod thin film over a wide temperature range (2 K < T < 350 K). The MnP nanorod films of ~100 nm thickness were grown on Si substrates at 500 °C using molecular beam epitaxy. The temperature-dependent resistivity ρ(T) data exhibit a metallic behavior (dρ/dT > 0) over the entire measured temperature range. However, large negative magnetoresistance (Δρ/ρ) of up to 12% is observed below ~50 K at which the system enters a stable helical (screw) magnetic state. In this temperature regime, the Δρ(H)/ρ(0) dependence also shows a magnetic field-manipulated CONE + FAN phase coexistence. The observed magnetoresistance is dominantly governed by the intergranular spin dependent tunneling mechanism. These findings pinpoint a correlation between the transport and magnetism in this helimagnetic system. Full article

This study focused on perforated bricks, and the structural performance enhancement of brick members by internal reinforcement was experimentally investigated. As a new reinforcing material, screw iron (SI) rods were selected for the internal reinforcement, and they were inserted into the perforated brick. To investigate the most-effective reinforcing method as well as to understand the fundamental structural behaviors, four specimens with different variables were fabricated, and three-point bending tests were carried out. From the experiments, it was found that the maximum strength of the specimen increased by more than two times with internal reinforcement. The internal reinforcement, fixed by nuts at both ends of the specimen to enhance integrity, increased the maximum strength by nine times. Moreover, the deformation capacities of the specimens were also greatly enhanced. The case where the internal SI rods were fixed by nuts without mortar also showed a similar structural performance to the case with mortar. The estimation methods of the maximum strength of the specimens were also discussed, and they showed reasonable agreement with the test results. It was proved that the proposed material and methods enabled effective utilization of the internal reinforcement, and they could contribute to the improvement of structural performances in masonry construction. Full article

A moving pair with two-body contact is the ideal situation assumed in previous analyses. However, all moving pairs are in a three-body contact state at the start of operation or immediately after the start of operation, such as bearings, ball-screws, gears and engines. This work studies the influence of wear particles (SUJ2), environmental particles (SiO₂ and Al₂O₃) and nano-additives (CuO) on the tribological contact characteristics under different particle concentrations, particle sizes, surface roughnesses and contact modes. The three-body microcontact analysis revealed that the differences in the real contact area, particle contact area and separation of the four-particle materials in the three-body s–s and p–s contact modes are rather small. Under the three-body hybrid contact mode, the difference is relatively large and the sequence of the real contact area value obtained due to the elastic modulus for the four-particle material at this interface is Al₂O₃ > SUJ2 > CuO > SiO₂. The order of the other two contact characteristics is reversed. The difference increases as the particle size or particle concentration increases. The order of the critical load required to transform three kinds of contact modes is SiO₂ > CuO > SUJ2 > Al₂O₃. On the nearly initial three-body hybrid contact mode, the plastic contact area ratio at the interface first increases to a critical value and then decreases as the load increases because the original plastic contact spot area and contact spot number increases with the increase in load. At the same time, the elasto-plastic contact area ratio decreases to a low value and then increases. The elastic contact area ratio at the interface decreases as the load increases. Among the four third-particle materials, the experimental results and theoretical predictions show that the environmental particles, Al₂O₃, cause the maximum friction and wear observed at the interface. Full article

This article presents a new technology for forming automotive connecting rod forgings by means of die forging from cast performs from EN AB-71100 (EN AB-AlZn10Si8Mg) aluminum alloy. A premise was made that the production process would be carried out on forging presses. The process of forming connecting rod forgings was analyzed considering different deformation rates related to the type of machine used: a crank press and a screw press. The billet in the form of in-house designed, shaped preforms cast into sand molds with two variants of geometry was used in the process. The numerical analysis of the new process was carried out on the basis of the finite element method using Deform 3D, the simulation software for metal forming. The simulations were conducted in the spatial deformation conditions, considering the full thermomechanical analysis. Based on the simulations, certain important findings concerning the novel process were acquired, including the distribution of stress, deformation, temperatures, cracking criterion and energy parameters. The results of numerical tests confirmed the possibility of producing defect-free forgings of connecting rods from EN AB-71100 aluminum alloy on forging presses by means of the proposed technology. The proposed process of forging using crank and screw presses was verified in the course of tests conducted in industrial conditions. The properly formed connecting rod forgings were subjected to quality tests in terms of their structure and mechanical properties. Full article

Corn starch was plasticized by glycerol suspension in a twin-screw extruder, in which the glycerol suspension was the pre-dispersion mixture of glycerol with nano-SiO₂. Polylactide (PLA)/thermoplastic starch/SiO₂ composites were obtained through melt-blending of PLA with thermoplastic starch/SiO₂ in a twin-screw extruder. The nonisothermal crystallization behavior of PLA in the composites was investigated by differential scanning calorimetry. An interface of PLA with thermoplastic starch was proven to exist in the composites, and its interfacial bonding characteristics were analyzed. The interfacial binding energy stemming from PLA with thermoplastic starch exerts a significant influence on the segmental mobility of PLA at the interface. The segmental mobility of PLA is gradually improved by increasing interfacial binding energy, and consequently, the relative crystallinity on the interface exhibits progressive promotion. The Jeziorny model could well describe the primary crystallization of PLA in the composites. The extracted Avrami exponents based on the Jeziorny model indicate that the primary crystallization of PLA follows heterogeneous nucleation and three-dimensional growth. This study has revealed the intrinsic effect of the interfacial segmental mobility on the nonisothermal crystallization behavior of PLA in composites, which is of technological significance for its blow molding. Full article

Here, we report on the epitaxial growth of GaN on patterned SiO₂-covered cone-shaped patterned sapphire surfaces (PSS). Physical vapor deposition (PVD) AlN films were used as buffers deposited on the SiO₂-PSS substrates. The gallium nitride (GaN) growth on these substrates at different alternating radio frequency (RF) power and nitridation times was monitored with sequences of scanning electron microscopy (SEM) and atomic force microscopy (AFM) imaging results. The SEM and AFM show the detail of the crystalline process from different angles. Our findings show that the growth mode varies according to the deposition condition of the AlN films. We demonstrate a particular case where a low critical alternating current (AC) power is just able to break SiO₂ covalent bonds, enabling the growth of GaN on the sides of the patterns. Furthermore, we show that by using the appropriate nitridation condition, the photoluminescence (PL) integral and peak intensities of the blue light epi-layer were enhanced by more than 5% and 15%, respectively. It means the external quantum efficiency (EQE) of epitaxial structures is promoted. The screw dislocation density was reduced by 65% according to the X-ray diffraction (XRD) spectra. Full article

This work aims to produce a 3D-printable bio-based filament composed of high-density polyethylene (HDPE) and chemically modified cellulose nanofibrils. Printing using HDPE as a raw material is challenging due to its massive shrinkage and warping problems. This paper presents a new method to overcome those difficulties by enhancing the mechanical properties and achieving better print quality. This was achieved using modified cellulose nanofibrils (CNFs) as fillers. Firstly, CNF was converted to a CNF-based macroinitiator through an esterification reaction, followed by a surface-initiated single-electron transfer living radical polymerization (SI-SET-LRP) of the hydrophobic monomer stearyl acrylate. Poly stearyl acrylate-grafted cellulose nanofibrils, CNF-PSAs, were synthesized, purified and characterized with ATR-FTIR, ¹³C CP-MAS NMR, FE-SEM and water contact angle measurements. A composite was successfully produced using a twin-screw extruder with a CNF-PSA content of 10 wt.%. Mechanical tests were carried out with tensile testing. An increase in the mechanical properties, up to 23% for the Young’s modulus, was observed. A morphologic analysis also revealed the good matrix/CNF compatibility, as no CNF aggregates could be observed. A reduction in the warping behavior for the composite filament compared to HDPE was assessed using a circular arc method. The 3D printing of complex objects using the CNF-PSA/HDPE filament resulted in better print quality when compared to the object printed with neat HDPE. Therefore, it could be concluded that CNF-PSA was a suitable filler for the reinforcement of HDPE, thus, rendering it suitable for 3D printing. Full article

Wafer-scale on-axis 4H-SiC epitaxial layers with very low roughness were obtained in this study. By performing carbon-rich hydrogen etching and epitaxial growth of the epitaxial layer at different temperatures, local mirror regions (LMRs) with root mean square (RMS) roughness less than 0.2 nm were obtained on the epitaxial layer surface. The LMRs’ length is tens of millimeters, and the width is sub-millimeters. The step-flow growth induced by threading screw dislocations (TSDs) was observed on the epitaxial layer surface by atomic force microscopy (AFM), together with the double bi-atomic step-flow growth induced by the step bunch, which was the cause of LMRs. Furthermore, the growth mechanism was investigated by wet etching. The etching pits were found to be associated with 3C-SiC and their effect on the growth rate of epitaxial layers was further explored. Full article

Poly(2,6-dimethyl-1,4-phenylene oxide)/polyamide 11 (PPO/PA11 80/20) blend filled with neat (SiO₂) or modified silica having amine functional groups (A-SiO₂) was melt mixing in a twin-screw extruder. The silica was prepared by the sol–gel process. SEM shows that, with increasing A-SiO₂ content from 1 to 5 wt.%, the morphology of PPO/PA11blend changed from droplet matrix to co-continuous with phase inversion. The phase inversion was also observed for 5 wt.% of neat silica, but the droplet-matrix structure was retained. The overall rheological and mechanical properties improvement of the A-SiO₂-filled composites in comparison with the unfilled blend and neat silica counterpart was drastic, especially in terms of viscosity and stiffness. A-SiO₂ improved PPO and PA11 miscibility and reduced the crystallinity of PA11, without affecting the T_c, owing to the compatibilization effect. On the other hand, neat silica slightly increased the crystallinity of PA11 and decreased the crystallization temperature of PA11 and the glass transition temperature of PPO as a result of its plasticization. Full article

The melt-back process has a significant effect on the quality of solution-grown SiC crystals. However, the phenomena surrounding the SiC dissolution into the molten alloy during the melt-back process have not been clarified. In this study, the behavior of 4H-SiC dissolution into molten alloy was investigated by using high-temperature in situ observation and subsequent KOH etching, and the effects of different doping conditions and crystal polarity were studied. Local dissolutions with hexagonal pyramid-shape originating from threading screw dislocation (TSD) were observed on the C face of n-type SiC with light nitrogen doping. Our analysis of their behavior revealed that the process was governed by the spiral dissolution. In addition to the dissolution at TSD, local dissolutions at threading-edge dislocations were observed on the Si face of the same crystal. The shape of the local dissolution at the dislocation was significantly affected by the doping conditions and the polarity of the SiC crystal. This local dissolution may occur during the melt-back process, suggesting that it is important to promote the dissolution while maintaining a smooth interface through the selection of the seed crystal and by keeping the degree of interface undersaturation small. Full article