Search Results (218)

Chainsaws are widely used in various occupational settings, including forestry, landscaping, farming, and by homeowners for tasks like tree felling, brush clearing, and firewood cutting. However, the use of chainsaws poses significant risks to operators and bystanders. This research quantified and compared occupational and nonoccupational injuries caused by contact with chainsaws and related objects during the period from 2018 to 2022. The emergency department and OSHA (Occupational Safety and Health Administration) data were used to characterize the cause and nature of the injuries. Results suggest that for this five-year period an estimated 127,944 people were treated in U.S. emergency departments for chainsaw-related injuries. More than 200 non-fatal and 57 fatal occupational chainsaw-involved injuries were found during the same period. Landscaping and forestry were the two industries where most of the occupational victims were employed. Upper and lower extremities were the most likely injured body parts, with open wounds from cuts being the most common injury type. The majority of fatal injuries were caused by falling objects such as trees and tree limbs while using a chainsaw. Our suggestions to reduce injuries include proper training and wearing personal protective equipment, as well as making sure any bystanders are kept in a safety zone away from trees being cut. Full article

This study analyzes 209 dog skeletons from two sites in Wolin (9th–mid-13th century AD) using 100 standard metric variables covering cranial, mandibular, and postcranial elements. Estimated withers height, body mass, age at death, and sex were derived using established methods. The results indicate the presence of at least two to three morphotypes: small spitz-like dogs (40–50 cm, 4–6 kg), medium brachycephalic forms (50–60 cm, 10–15 kg), and larger mesocephalic individuals (up to 65 cm, 20–40 kg). Dogs lived 3–10 years, with both sexes represented. Signs of cranial trauma and dental wear suggest utilitarian roles such as guarding. The size range and morphological diversity point to intentional breeding and trade-based importation. Small dogs likely served as companions or city guards, while medium and large types were used for herding, hunting, or transport. These findings highlight Wolin’s role as a dynamic cultural and trade center, where human–dog relationships were shaped by anthropogenic selection and regional exchange. Full article

The aim of translucency-enhancing liquids (TEL) is to locally influence the phase composition of zirconia in order to increase its translucency. This study aimed to determine the influence of TEL on 3Y- and 4Y-TZP zirconia concerning roughness, hardness, wear, flexural strength, dynamic stability and fracture force of fixed dental prostheses after thermal cycling and mechanical loading. Two zirconia materials (4Y-TZP; 3Y-TZP-LA, n = 8 per material and test) were investigated with and without prior application of TEL. Two-body wear tests were performed in a pneumatic pin-on-block design (50 N, 120,000 cycles, 1.6 Hz) with steatite balls (r = 1.5 mm) as antagonists. Mean and maximum vertical loss as well as roughness (Ra, Rz) were measured with a 3D laser-scanning microscope (KJ 3D, Keyence, J). Antagonist wear was determined as percent area of the projected antagonist area. Martens hardness (HM; ISO 14577-1) and biaxial flexural strength (BFS; ISO 6872) were investigated. The flexural fatigue limit BFSdyn was determined under cyclic loading in a staircase approach with a piston-on-three-ball-test. Thermal cycling and mechanical loading (TCML: 2 × 3000 × 5 °C/55 °C, 2 min/cycle, H₂O dist., 1.2 × 10⁶ force á 50 N) was performed on four-unit fixed dental prostheses (FDPs) (n = 8 per group) and the fracture force after TCML was determined. Statistics: ANOVA, Bonferroni test, Kaplan–Meier survival, Pearson correlation; α = 0.05. TEL application significantly influences roughness, hardness, biaxial flexural strength, dynamic performance, as well as fracture force after TCML in 3Y-TZP. For 4Y-TZP, a distinct influence of TEL was only identified for BFS. The application of TEL on 3Y- or 4Y-TZP did not affect wear. TEL application has a strong effect on the mechanical properties of 3Y-TZP and minor effects on 4Y-TZP. All effects of the TEL application are of a magnitude that is unlikely to restrict clinical application. Full article

Background: Artificial tooth wear impacts prosthesis durability and function; understanding material–antagonist interactions guides clinical choices. Aim: This in-vitro study aimed to assess the wear behavior of isosit and nanohybrid composite resin artificial teeth when opposed to various antagonist materials using 3D volumetric wear analysis. Materials and Methods: Sixty specimens (n = 10 per group) were prepared from two artificial tooth materials and assigned to six antagonist combinations: isosit–isosit, isosit–nanohybrid composite, isosit–porcelain, nanohybrid composite–isosit, nanohybrid composite–nanohybrid composite, and nanohybrid composite–porcelain. Specimens were scanned before and after 600,000 chewing cycles using a structured-light 3D scanner. Volumetric wear was calculated by superimposing pre- and post-test scans. Data were analyzed using two-way ANOVA and Tukey’s HSD test (α = 0.05). Results: Porcelain antagonists produced the highest wear values (p < 0.05). No significant difference was found between isosit and nanohybrid antagonists (p > 0.05). Identical material pairings showed less wear, though differences were not statistically significant. Conclusions: Porcelain as an antagonist increased wear risk. Using identical materials bilaterally, such as isosit–isosit or nanohybrid–nanohybrid, may help reduce artificial tooth wear in removable prostheses. Full article

Sewing is the major contributor to the manufacturing of protection wear for the survival of early human civilization against extreme weather conditions. Mechanized sewing witnessed developments during the middle of the 19th century, and tedious handwork was replaced by sewing machines. Despite the modernization of sewing machine technologies, speed, material thicknesses, automation, and the introduction of AI in sewing, there is a longstanding problem of heat loss along stitch lines. The sewing material is compressed by the sewing thread, and this compression results in a bridge between the human body and the external cold environment. Garment technologists identify this problem and due to the lack of any technological solution, the problem is solved through complex material handling methods. A new sewing technological solution has been developed to solve this problem, called spacer stitching, which addresses the problem of compression along stitch lines. Two baffled jackets with sewn-through methods are prepared, one with the spacer stitching technology and the other with conventional sewing. Thermal resistance and insulation efficiency are evaluated using the Thermetrics thermal manikin “Sonny” under dynamic (walking) conditions to analyze the thermal resistance difference between the two types of sewing methods as well as the effects of motion on insulation. The results reveal that the jacket made with spacer stitching demonstrates significantly higher thermal resistance and enhanced wearer comfort compared to that produced using conventional methods. Additionally, variations in thermal resistance are observed across different zones of the thermal manikin. These findings highlight the potential of spacer stitching to improve thermal insulation and revolutionize high-performance outerwear design. Full article

This paper addresses inherent limitations in unmanned aerial vehicle (UAV) undercarriages hindering vertical takeoff and landing (VTOL) capabilities on uneven slopes and obstacles. Robotic landing gear (RLG) designs have been proposed to address these limitations; however, existing designs are typically limited to ground slopes of 6–15°, beyond which rollover would happen. Moreover, articulated RLG concepts come with added complexity and weight penalties due to multiple drivetrain components. Previous research has highlighted that even a minor 3-degree slope change can increase the dynamic rollover risks by 40%. Therefore, the design optimization of robotic landing gear for enhanced VTOL capabilities requires a multidisciplinary framework that integrates static analysis, dynamic simulation, and control strategies for operations on complex terrain. This paper presents a novel, hybrid, compliant, belt-driven, three-legged RLG system, supported by a multidisciplinary design optimization (MDO) methodology, aimed at achieving enhanced VTOL capabilities on uneven surfaces and moving platforms like ship decks. The proposed system design utilizes compliant mechanisms featuring a series of three-flexure hinges (3SFH), to reduce the number of articulated drivetrain components and actuators. This results in a lower system weight, improved energy efficiency, and enhanced durability, compared to earlier fully actuated, articulated, four-legged, two-jointed designs. Additionally, the compliant belt-driven actuation mitigates issues such as backlash, wear, and high maintenance, while enabling smoother torque transfer and improved vibration damping relative to earlier three-legged cable-driven four-bar link RLG systems. The use of lightweight yet strong materials—aluminum and titanium—enables the legs to bend 19 and 26.57°, respectively, without failure. An animated simulation of full-contact landing tests, performed using a proportional-derivative (PD) controller and ship deck motion input, validate the performance of the design. Simulations are performed for a VTOL UAV, with two flexible legs made of aluminum, incorporating circular flexure hinges, and a passive third one positioned at the tail. The simulation results confirm stable landings with a 2 s settling time and only 2.29° of overshoot, well within the FAA-recommended maximum roll angle of 2.9°. Compared to the single-revolute (1R) model, the implementation of the optimal 3R Pseudo-Rigid-Body Model (PRBM) further improves accuracy by achieving a maximum tip deflection error of only 1.2%. It is anticipated that the proposed hybrid design would also offer improved durability and ease of maintenance, thereby enhancing functionality and safety in comparison with existing robotic landing gear systems. Full article

The aim of this study was to evaluate the influence of filler type, filler content, and filler silanization on the flexural strength (FX), elastic modulus (E_m), shore D hardness (SDH), and two-body wear (2BW) of polyaryletherketone (PAEK) compounds. Specimens (40 wt% PEEK, 40 wt% PEK) with different filler types: 20 wt%: fumed silica (FS), calcium silicate (CS), feldspar (FP), magnesium silicate hydrate (MSH), no filler (NF); different filler content: 20, 25 or 30 wt% CS; different filler silanization: 20 wt% CS silanized with alkylsilane/aminosilane, FP silanized with methylsilane/ vinylsilane, no silanization; and PEEK₂₀ (BioHPP) or PEEK₂₅ (BioHPP plus) controls were fabricated and tested for FX, E_m, and SDH. Two-body wear (4 × 100,000 cycles, 50 N, 2.5 Hz) with composite resin antagonists was measured with PAEK_i (35 wt% PEEK, 35 wt% PEK, 30 wt% CS), PAEK_ii (70 wt% PEEK, 30 wt% CS), PAEK_iii (70 wt% PEEK, 25 wt% CS, 5 wt% FP), and PEEK₂₀ controls. Data were analyzed with Kolmogorov–Smirnov-, Kruskal–Wallis-H-, post hoc Scheffé test, pairwise comparisons, Bonferroni correction, one-way ANOVA, and Spearman rho (α = 0.05). An abrasion area analysis was performed. Adding filler increased FX, E_m, and SDH, with CS and MSH showing the highest values for FX and E_m. Adding 30 wt% CS increased FX, E_m, and SDH compared with 20 wt%. Silanization with methylsilane increased FX, E_m, and SDH. Silanization with aminosilane increased FX and SDH. PEEK₂₀ showed the lowest 2BW compared with all EPCs. No material losses were detected on the antagonists. PAEK compounds with 25 to 30 wt% CS increased FX and E_m compared to lower contents, no filler, or PEEK₂₀. Higher values of FX and E_m did not lead to lower 2BW. Full article

Background: In the fields of rehabilitation, public health, military training and other domains, the accurate and effective monitoring of exercise intensity during exercise can control the occurrence of sports injuries, which is of great significance for people’s healthy lives. Objective: This study combined easily collectable multi-dimensional sensor data and various algorithm models to achieve cross-individual recognition of low, middle and high levels of exercise intensity. Methods: This study compared the recognition performance of different algorithm models using acceleration and angular velocity sensors worn on seven body parts through individualised body data characteristics. Results: The recognition performances of two classical machine learning algorithms were the worst, with a recognition rate of only 82.97% and 80.31%. The performances of two ensemble learning algorithms were slightly better, with a recognition rate of 88.86% and 87.35%. The deep sub-domain adaptation network algorithm proposed in this study exhibited the best performance, with a recognition rate of 92.87%. This study utilised multi-dimensional sensors to construct a cross-individual exercise intensity recognition model for different parts of the body, and the overall recognition rate of the left part was higher than that of the right part. Moreover, the recognition effect upon wearing sensors on the left side of the body is better than the right in running events. Conclusions: The results of this study have demonstrated the effectiveness of combining domain adaptation methods and multi-dimensional sensors for cross-individual exercise intensity recognition, laying a solid theoretical foundation for broader-scale cross-individual exercise intensity recognition in future research. Full article

Laser-boronized parts manufactured by a selective laser melting process from 18Ni to 300 maraging steel are investigated in this study. Two main issues are addressed, namely (i) the possibility to restore the hardness of the heat-affected zone (HAZ) formed during laser processing and (ii) the effect of re-aging on the hardness and wear resistance of the laser-boronized layer with a hypoeutectic structure. Optical microscopy, scanning electron microscopy, energy-dispersive spectroscopy, X-ray diffraction analysis, microhardness measurements, the “ball-on-plate” dry sliding test, and the two-body dry abrasive wear test were employed to answer the questions. The results confirmed that HAZ is formed with the dissolution of intermetallides formed before and undergo full (near the molten pool) or partial (at some distance from the molten pool) iron–base matrix recrystallization. The hardness of HAZ (350–550 HK0.05) has been restored after re-aging to the 550–600 HK0.05 level. Moreover, a certain positive effect of re-aging on the laser-boronized layer with a hardness of ~470–750 HK0.2 is established, associated with structural transformations induced by aging in the iron-based solid solution phase. The hardness increased by ~9–25%. The wear resistance of the hardest boronized samples (~750 HK0.2) under dry sliding and dry abrasive wear conditions was ~5.8 times and 3.7 times higher than that of the aged control sample, while re-aging provided further improvement of these characteristics. The presented results provide insights into the effectiveness of laser-boronized layers having a hypoeutectic structure in terms of increasing the wear resistance of maraging steel. Full article

Bone diseases lead to an increasing demand for implants to treat long bone defects and for load-bearing applications. Osteoporosis care and accidental injuries are major contributors to this rising need. Our research aims to demonstrate innovative material systems and methods for preparing implants that can be used in regenerative medicine. We hypothesize that by combining titanium alloys (Ti6Al4V) with hydroxyapatite (Hap), we can enhance biocompatibility and tribo-mechanical performance, which are critical for the longevity of Ti-based surgical implants. Additionally, we investigate the application of laser surface treatments to expose the underlying porosity, thereby enhancing cell transport and promoting cell growth. In this study, we investigate the effects of two fabrication techniques—Spark Plasma Sintering (SPS) and powder metallurgy (PM)—on the properties of laser-textured Ti64/Hap biocomposites. Our findings demonstrate that the selected processing route significantly influences the microstructure, tribological performance, and surface properties of these materials. An X-ray diffraction (XRD) analysis corroborates our results from incubation studies in simulated body fluids, highlighting the impact of phase transformations during sintering on the chemical properties of Ti-Hap composites. Additionally, while laser surface texturing was found to slightly increase the friction coefficient, it markedly enhanced the wear resistance, particularly for the PM and SPS Ti + 5%Hap composites. Full article

Background: The rapidly growing elderly population in Sri Lanka faces multiple challenges, including the ill effects of tooth loss. Tooth loss and denture wear could both affect the amount and variety of food intake of the elders, leading to a state of compromised health. Therefore, it is essential to identify whether both tooth loss and denture wear affect the nutritional status of the elderly. This study evaluated the associations between tooth loss, denture-wearing status, and nutritional levels among a sample of the elderly population attending the Dental Teaching Hospital in Peradeniya, Sri Lanka. Methods: An analytical cross-sectional study was carried out at the Dental Teaching Hospital in Peradeniya, Sri Lanka. Using the G*Power v3.1 statistics software, a sample size of 61 patients aged 60 years and above was determined as the minimum sample size. Data were gathered by means of a self-administered questionnaire, patients’ files, and an examination to identify height and weight for assessing body mass index (BMI). Minitab v18.0 statistical software was used for analysis of data, and a p-value < 0.05 was considered statistically significant. Results: One hundred patients were recruited for this study, and the majority (sixty-seven) were female. The majority (71%) were between the ages of 60 to 69 years. The majority (60%) were denture wearers and 8% had nine or more occluding pairs (of natural teeth), 25% had five to eight, and 67% had four or fewer occluding pairs. Fifty-two percent (52%) were of normal weight, while 40% were over-weight and 8% were underweight, respectively. No statistically significant associations were identified between BMI and the denture status or number of missing teeth (p-values > 0.05). There were no statistically significant associations between the underweight or overweight status and denture wearing or occluding pairs (p-values > 0.05). However, the frequency of grain intake and the number of occluding pairs were significantly associated with each other (p-value = 0.024). Also, the frequency of taking snacks was associated with denture wearing (p-value = 0.006). Conclusions: The nutritional status (BMI) of the elderly does not necessarily correlate with their denture-wearing status or the number of existing occluding pairs/number of missing natural teeth. There is no significant association noted between the denture-wearing status and the food avoidance (soft, hard food, fruits, and grains, except snacks). There is no significant association between the number of occluding pairs available in natural dentition and the avoidance of soft foods or snacks, except for grains. Given the limitations of this study, it can be suggested that nutritional strategies for the elderly population could be designed universally, irrespective of their dentate or denture status. However, further research with a larger cohort is needed to validate these findings. Full article

Wear resistance is of paramount importance for the long-term success of dental materials, especially when they are used for extensive indirect restorations in full-mouth rehabilitations. The present in vitro study aimed to evaluate the two-body wear resistance of a new and recently introduced CAD/CAM resin composite disc (Ena Cad, Micerium S.pA.), to compare it to the wear resistance of other two well-known and already marketed CAD/CAM composites (Brilliant Crios, Coltene/Whaledent AG; Grandio disc, Voco Gmbh) and to a conventional type 3 gold alloy (Aurocast 8, Nobil-Metal). Ten cylindrical specimens (diameter 8 mm, height 6 mm) were manufactured with each material and subjected to a two-body wear test in a dual-axis chewing simulator, performing 120,000 chewing cycles opposing antagonists (2-mm-diameter round tip) made out of the same corresponding materials. The total vertical wear (mm) and the total volumetric loss (mm³) for each sample/antagonist pair were calculated. Representative scanning electron microscope images were also taken. Data were statistically analyzed using one-way analysis of variance tests. No statistically significant differences were recorded among the wear properties of the restorative materials under investigation. The Ena Cad disc showed a wear resistance comparable to the type 3 gold alloy and to the already marketed Brilliant Crios and Grandio disc. Full article

Traditional VO_2max testing methods are often impractical for manual wheelchair users, as they rely on lower-body exercise protocols, require specialized equipment, and trained personnel. The 6-Minute Push Test (6MPT) is a widely used cardiovascular assessment that may provide a feasible alternative for estimating aerobic capacity in this population. This study aimed to develop a predictive model for VO_2max using physiological variables recorded during the 6MPT. Twenty-eight participants (14 novice and 14 expert manual wheelchair users) completed the test while wearing a VO₂ mask and heart rate monitor. Spearman correlation analysis showed that distance covered during the 6MPT significantly correlated with VO_2max (r = 0.685, p < 0.001). A stepwise linear regression identified two predictive models: one using distance alone (R² = 0.416, p < 0.001) and another incorporating both distance and maximum heart rate (R² = 0.561, p < 0.001). These models offer practical estimations of VO_2max, eliminating separate protocols. Our findings suggest that the 6MPT can serve as a simple, cost-effective alternative to laboratory-based VO₂ testing, facilitating routine cardiovascular fitness assessments for manual wheelchair users in clinical and community settings. Future research should focus on validating these models in a larger, more diverse cohort to enhance their generalizability. Full article

Objectives: Slag injuries in industrial settings pose risks of hearing loss and complications. The aim of this study is to provide specialists with a better understanding of the sequelae, treatment, and long-term outcomes that a patient may have following a slag injury to the tympanic membrane. Data Sources: PubMed, Embase, and Web of Science. Methods: Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA), multiple databases were queried for articles published from inception to 2023 describing Tympanic membrane injuries from welding. The publications were screened by two independent viewers. The Joanna Briggs Institute 2017 Critical Appraisal Checklist was used to assess the quality of studies. Results: A total of 227 articles were identified, and 9 full-text articles were included in this review, comprising a total of 18 patients. The patients’ ages ranged from 18 to 75 years. Most commonly, patients were welding overhead in a tight working space, and none of the patients were wearing protective ear equipment in addition to their welding masks. Patients experienced otalgia (n = 10; 55%), hearing loss (n = 11; 65%), vertigo (n = 6; 35%), chronic otorrhea (n = 5; 29%), and facial paralysis (n = 4; 23%). A total of 12 patients (70.6%) required surgery, most requiring debridement of metallic foreign body multiple times, some undergoing surgery up to four years post-injury. Conclusions: Tympanic membrane injuries from welding are often overlooked. They cause hearing loss and facial nerve damage. Following a period of observation, sturdy reconstruction with cartilage grafting is recommended, given the poor vasculature and inflammation after this injury. Full article

This study aims to achieve in situ-formed pure Ti and Ti6Al4V coatings on 316L stainless steel through hot pressing and examine their wear and corrosion properties thoroughly in two simulated body fluids: physiological serum (0.9% NaCl) and Hanks’ solution. The sintering and diffusion bonding process was conducted at 1050 °C under a uniaxial pressure of 40 MPa for 30 min in a vacuum environment of 10⁻⁴ mbar. Following sintering, in situ-formed pure Ti and Ti6Al4V coatings, approximately 1000 µm thick, were produced on 316L substrates approximately 3000 µm in thickness. The mean hardness of 316L substrates, pure Ti, and Ti6Al4V coatings are around 165 HV, 170 HV, and 420 HV, respectively. The interface of the stainless steel substrate and the pure Ti and Ti6Al4V coatings exhibited no microstructural defects, while the interface exhibited significantly higher hardness values (ranging from 600 to 700 HV). The coatings improved corrosion resistance in both electrolytes compared to the 316L substrate. Wet wear tests revealed reduced friction coefficients in 0.9% NaCl relative to Hanks’ solution, highlighting the chemical interactions between the material surface and the electrolyte type and the significance of tribocorrosion in biocoatings. Full article