Search Results (164)

Source inversion optimization using sensor observations is a key method for rapidly and accurately identifying unknown source parameters (source strength and location) in abrupt hazardous gas leaks. Sensor number and location distribution both play important roles in source inversion; however, their combined impacts on source inversion optimization remain poorly understood. In our study, the optimization inversion method is established based on the Gaussian plume model and the generation algorithm. A research strategy combining random sampling and coefficient of variation methods was proposed to simultaneously quantify their combined impacts in the case of a single emission source. The sensor layout impact difference was analyzed under varying atmospheric conditions (unstable, neutral, and stable) and source location information (known or unknown) using the Prairie Grass experiments. The results indicated that adding sensors improved the source strength estimation accuracy more when the source location was known than when it was unknown. The impacts of sensor location distribution were strongly negatively correlated (r ≤ −0.985) with the number of sensors across scenarios. For source strength estimation, the impacts of the sensor location distribution difference decreased non-linearly with more sensors for known locations but linearly for unknown ones. The impacts of sensor number and location distribution on source strength estimation were amplified under stable atmospheric conditions compared to unstable and neutral conditions. The minimum number of randomly scattered sensors required for stable source strength inversion accuracy was 11, 12, and 17 for known locations under unstable, neutral, and stable atmospheric conditions, respectively, and 24, 9, and 21 for unknown locations. The multi-layer arc distribution outperformed rectangular, single-layer arc, and downwind-axis distributions in source strength estimation. This study enhances the understanding of factors influencing source inversion optimization and provides valuable insights for optimizing sensor layouts. Full article

(1) Background: The paper focuses on foot biomechanics in static situations. The aim was to determine the distribution of the load exerted by the human body on the ground in order to establish reference points on the foot for correct human body posture. (2) Methods: A model was developed to describe the body weight-ground relationship, consisting of a support platform and a part imitating the rest of the human body. Experiments consisted of tilting the general centre of gravity from the maximum forward through midfoot, a passive, neutral position, to the maximum backwards while maintaining balance. The ground load was measured in each position. (3) Results: The loads of the front and rear parts of the support platform and the resultant load force at different degrees of body tilt were calculated. It has been shown that at the maximum inclination of the body to the extreme support point, the entire weight falls on this point. For the neutral position (in the Basic Balance Point), the load on the front and rear parts of the support platform was 26% and 74%, and 40% and 60% for the passive position (in the Passive Balance Point). (4) Conclusions: The distribution of body weight on the ground is determined by the projection of the general centre of gravity on the ground through the feet. The resultant ground reaction force defines both the magnitude and direction of the load exerted on the support platform. Ground reaction forces associated with body weight were assessed at five anatomical points of the foot: the forefoot, rearfoot, midfoot, and the Passive and Basic Balance Point. In an upright standing posture, the projection of the general centre of gravity fluctuates between the Passive and Basic Balance Point, corresponding to the passive and neutral positions, respectively. Only in the neutral position, the body’s weight, as concentrated in the general centre of gravity, falls on the axis of the upper ankle joint and distributes the load between the forefoot and rearfoot. Determining the correct distribution of foot loads may serve in the future to study abnormalities in human body posture Full article

Recently, it has been shown that, under the action of the lateral van der Waals (vdW) force due to a perfectly conducting corrugated plane, a neutral anisotropic polarizable particle in vacuum can be attracted not only to the nearest corrugation peak but also to a valley or an intermediate point between a peak and a valley, with such behaviors called peak, valley, and intermediate regimes, respectively. In the present paper, we discuss how the curvature of the corrugated surface affects the occurrence of the mentioned regimes. For this, we calculate the vdW interaction between a polarizable particle and a grounded conducting corrugated cylinder. We consider the corrugations along the azimuthal ($\varphi$-direction) angle or along the cylinder axis (z-direction). We show that when the corrugation occurs in the z-direction, the curvature has a small effect on the occurrence of the valley regime. On the other hand, it inhibits the intermediate regimes up to a certain particle–surface distance above which it amplifies the occurrence of this regime. When the corrugation occurs in the $\varphi$-direction, we show that the curvature inhibits both the valley and intermediate regimes. Full article

This study focused on the advanced analysis of the crack resistance of reinforced concrete structures and provides proposals for improvement of the theory of calculation of reinforced concrete structures for serviceability and ultimate limit state. Despite the fact that the crack opening is a key parameter of reinforced concrete structures that frequently determines the reinforcement area, the design models and theory of calculation of this parameter are still not sufficiently perfect. The recent studies performed worldwide with the use of more advanced instrumentation have shown that the accuracy of theoretical prediction of crack opening in structures experiencing a complex stress–strain state, and especially structures made of high-strength concrete, fiber-reinforced concrete, lightweight concrete, and etc., remains unsatisfactory. This study analyzed and summarizes experimental studies of crack resistance of reinforced concrete structures and reveals new physical regularities in the deformation of concrete and steel reinforcement in zones adjacent to the crack. It introduces hypotheses that account for these regularities and proposes a general block model for calculating the width of irregular and single cracks in reinforced concrete structures under different stress states. In this model, crack opening is modeled by the double-cantilever element (DCE), which allows incorporation of the corresponding experimentally revealed effects and at the same time combines deformation parameters of both the theory of reinforced concrete and fracture mechanics. The DCE is two conventionally separated rigid cantilevers that include the crack surfaces, and are embedded on one side in the concrete at the neutral axis. On the other side, they are connected with reinforced steel bars crossing the crack. Using this model, a method for calculating the crack opening width in reinforced concrete structures with different types of cracks is proposed. The paper demonstrates the results of experimental investigations of crack resistance of simply supported and cantilever beams made of ordinary, light, and high-strength concrete. These results confirm the effects considered in the calculation model and the hypotheses accepted in the theory. The study also provides a physical explanation of the phenomena under consideration and shows acceptable agreement between theoretical and experimental values of crack opening calculated according to the proposed theory. Full article

Background: Robotic-assisted technology has become an increasingly utilized adjunct within the realm of primary total knee arthroplasty (TKA). Previous studies have shown that robotic-assisted total knee arthroplasty (raTKA) offers potential advantages of enhanced bony preparation and optimal implant alignment with equivalent long-term patient outcomes and component longevity in comparison to conventional TKA (cTKA). Furthermore, recent studies have identified the additional benefit of decreased surgeon physiologic stress with the use of raTKA. The purpose of this study was to compare differences in surgeon posture between primary raTKA and cTKA. Materials and Methods: We prospectively evaluated 103 consecutive primary TKA cases (48 raTKAs, 55 cTKAs) performed by three high-volume, fellowship-trained arthroplasty surgeons. Throughout each case, surgeons wore a posture-tracking device to evaluate time spent slouching. The threshold for slouching was set to 30 degrees of flexion from a neutral spinal axis. Demographic and operative factors were collected. Two-tailed tests and multivariate analysis were used to assess for differences between groups. Results: After controlling for individual surgeon differences in posture, we found a decrease in the percentage and duration of time spent slouching in raTKA cases compared to cTKA cases (42.4 vs. 72.5%, p < 0.001, 35.4 vs. 54.7 min, p = 0.037). On average, the use of the robot decreased surgeon slouching time by 19.3 min (26.6%, p < 0.001). Patient factors such as increased age and ASA 2 were also associated with favorable effects on posture (p < 0.001). Conclusions: Surgeons performing primary raTKA cases spend significantly less case time and case percentage in a slouched posture compared to conventional primary TKA cases. This suggests the potential for ergonomic benefit of robotic-assisted technology in primary TKA. Further research is needed to determine the long-term effects of posture on surgeon pain and career longevity. Full article

Pancreatic ductal adenocarcinoma (PDAC) has one of the lowest 5-year survival rates of all cancers, and limited treatment options exist. Immunotherapy is effective in some cancer types, but the immunosuppressive tumor microenvironment (TME) of PDAC is a barrier to effective immunotherapy. CXCR2+ myeloid-derived suppressor cells (MDSCs) are abundant in PDAC tumors in humans and in mouse models. MDSCs suppress effector cell function, making them attractive targets for restoring anti-tumor immunity. In this study, we show that the most abundant soluble factors released from a genetically diverse set of human and mouse PDAC cells are CXCR2 ligands, including CXCL8, CXCL5, and CXCL1. Expression of CXCR2 ligands is at least partially dependent on mutant KRAS and NFκB signaling, which are two of the most commonly dysregulated pathways in PDAC. We show that MDSCs are the most prevalent immune cells in PDAC tumors. MDSCs expressed high levels of CXCR2, and we found that myeloid cells readily migrate toward conditioned media (CM) prepared from PDAC cultures. We designed CXCR2 ligand-Fc fusion proteins to modulate the CXCR2 chemotactic signaling axis. Unexpectedly, these fusion proteins were superior to native chemokines in binding and activation of CXCR2 on myeloid cells. These “superkines” were potent inhibitors of PDAC CM-induced myeloid cell migration and were superior to CXCR2 small-molecule inhibitors and neutralizing antibodies. Our findings suggest that CXCR2 superkines may disrupt myeloid cell recruitment to PDAC tumors, ultimately improving immunotherapy outcomes in patients with PDAC. Full article

Inhibin (INH) plays a key role in the regulation of the reproductive performance of geese. It inhibits follicle-stimulating hormone (FSH) secretion from the anterior pituitary gland to regulate spermatogenesis. Immunization against INH in male geese leads to the production of antibodies to neutralize the INH activity that enhances testicular function and gonadotropin production. The objectives of the present research were to elaborate on the effects of inhibin (INH) immunization on testicular histology, plasma LH, pituitary PRL mRNA, and hypothalamic VIP mRNA expressions in Yangzhou ganders. A total of 60 birds were selected and divided into control (CON) and INH-immunized (INH-immunized) groups, having 30 in each group. In this experiment, the ganders were immunized with INH three times, and birds in the CON group were inoculated with bovine serum albumin (BSA). The analyzed data revealed that immunization against inhibin had no significant effects on improving the plasma concentration of LH hormone; however, significant effects were observed on the germ cell line, hypothalamic VIP mRNA, and pituitary PRL mRNA expressions. It is concluded that INH (INH) immunization is an effective tool to improve reproductive efficiency in Yangzhou ganders; however, INH immunization may harm pituitary PRL mRNA and hypothalamic mRNA expressions and LH plasma concentration. Seasonality played a vital impact on the hypothalamus–pituitary–gonadal (HPG) axis. Full article

Ultra-high-performance fiber-reinforced concrete (UHPFRC) has the characteristics of high strength, toughness, and excellent crack resistance. In order to fully utilize the high-strength properties of UHPFRC and reduce the structural weight and construction cost, solid slabs can be fabricated into hollow-core slabs or composite sandwich slabs. In order to further analyze the mechanical properties and mechanism of action of UHPFRC hollow-core slabs, one solid slab and two hollow-core slabs with the same geometric dimensions, reinforcement, and steel fiber volume content are designed in this paper, and their stress performance under a static load was investigated using a four-point bending test. The research results show that the UHPFRC hollow-core slab is anisotropic, and the bending stiffness of the section with parallel, distributed tubes is slightly smaller than that of the solid slab. The addition of steel fibers can greatly limit the development of cracks on a slab surface, so the elastic limit of a UHPFRC hollow slab is higher than that of a conventional concrete hollow slab. The whole bending process is roughly divided into the elastic stage, the elastic–plastic stage, and the plastic stage; the crack development process on the bottom of the slab can be classified into the cracking stage, the stable crack development stage, and the rapid propagation stage. In the elastic stage, the cross-sectional deformation of the UHPFRC hollow-core slab in the bending process still satisfies the assumption of a flat section. A row of parallel, round tubes on the neutral axis has a little effect on the cracking load, bearing capacity, and deformation capacity of the UHPFRC slab. By conducting the comparative analysis of the hollow rate and bearing capacity, when the hollow rate reaches 13.57%, the comprehensive weight of the solid slab is reduced by 13.16%, the cracking moment is slightly reduced, and the ultimate load is only reduced by 8.78%. Under the premise of meeting the bearing capacity, the hollow rate of the UHPFRC hollow-core slab can be appropriately increased to save money and energy. Full article

Background: Robotic assistance is considered capable of improving precision and outcomes of total knee replacement. We assessed the inherent biases, pre-procedural planning accuracy using 2D to 3D X-Atlas^®, and final knee axis outcomes of the ROSA^® Knee System (Zimmer Biomet, Warsaw, IN, USA). Methods: A total of 55 patients who underwent robotic-assisted knee replacement using ROSA^® Knee System (Zimmer Biomet, Warsaw, IN, USA) at a single center were included. Pre-procedural measurements performed by ROSA were compared to those performed by senior consultants. Component sizes predicted by ROSA^® were compared to those implanted. A final axis measurement was taken during the procedure. Results: Femur components were exactly matched in (83.64%) cases, accurately matched in a further 8 (14.55%), and inaccurately matched for only 1 (1.82%). Tibial component sizes were exactly matched by the planning for 39 (70.91%), accurately for 12 (21.82%), and inaccurately for 4 (7.27%). ANOVA did not show statistically significant differences between the predicted and implanted femur (p = 0.96) nor the tibia components (p = 0.27). We show that ROSA^® pre-procedural planning has a statistically significant bias (p = 0.001), with a deviation of 0.83 degrees into varus, when assessing the knee axis in the coronal plane, compared to senior consultant measurements. The average of the final coronal knee axis was 0.37 degrees in varus (SD = 2.49). Conclusions: ROSA^® accurately predicts implanted component sizes. Despite the small and statistically significant varus bias in initial knee axis assessment, the system results lay within the ±3° of neutral knee axis, which is the widely accepted knee replacement standard. Full article

The frequency and buckling characteristics of functional gradient (FG) beams with asymmetric material distribution in the temperature field are analyzed in this paper. Generally, the asymmetrical material distribution of FG beams results in a non-zero neutral axis and non-zero thermal moment. However, some previous studies adopted the treatment of homogeneous beams in which the neutral axis and thermal moment were set as zero. To this end, a comprehensive FG beam model with thermal effect is developed based on the absolute nodal coordinate formulation, in which Euler–Bernoulli beam theory, Lagrangian strain, exact curvature, thermally induced strain, and neutral axis position are considered. For the convenience of comparisons, the presented model can be simplified into three models which do not consider the neutral axis or thermal moment. The numerical results indicate that the influence of the neutral axis on the thermal axial force is minimal while that on the thermal moment is significant. In the case of the high temperature difference, frequency, critical temperature difference, unstable state, and the buckling type of the FG beams are misjudged when the neutral axis or thermal moment is ignored. Full article

Background: The objective of this study was to compare the outcomes between patients undergoing mechanically aligned conventional total knee arthroplasty (MA-CTKA) and functionally aligned robotic-arm-assisted TKA (FA-RTKA). Methods: We reviewed a prospectively collected database of consecutive patients who underwent primary total knee arthroplasty (TKA) for knee osteoarthritis between June 2022 and May 2023. Patients were divided into two groups—MA-CTKA (n = 50) and FA-RTKA (n = 50)—based on the introduction of a robotic-arm-assisted system during the study period. The hip–knee–ankle (HKA) angle, joint line orientation angle (JLOA) relative to the floor, and weight-bearing line (WBL) ratio were evaluated using full-length standing hip-to-calcaneus radiographs to compare the conventional mechanical axis (MA) and the ground mechanical axis (GA) passing through the knee joint between the groups. Clinical outcomes were also compared between the two groups. Results: There were no significant differences in the postoperative HKA angle between the groups, due to discrepancies in the targeted alignment strategies (FA-RTKA: 2.0° vs. MA-CTKA: 0.5°; p = 0.001). The postoperative JLOA in the FA-RTKA group was more parallel to the floor, whereas the MA-CTKA group showed a downward angulation toward the lateral side (0.6° vs. −2.7°; p < 0.001). In the FA-RTKA group, the GA passed through a neutral position when accounting for the calcaneus, while the MA-CTKA group showed a more lateral GA position (48.8% vs. 53.8%; p = 0.001). No significant differences in clinical outcomes were shown between the FA-RTKA and MA-CTKA groups, with the FA-RTKA group demonstrating higher Forgotten Joint Scores and a greater range of motion (all p < 0.05). Conclusions: Functionally aligned TKA demonstrated improved joint line parallelism to the floor and more neutral weight-bearing alignment in the GA compared to mechanically aligned TKA. These findings indicate a more balanced load distribution across the knee, which may contribute to the superior clinical outcomes observed in the functionally aligned group. Full article

With increasing global concern over carbon emissions in the construction industry, cross-laminated-thick veneer (CLTV) has emerged as an innovative green building material with significant potential to promote the achievement of “dual-carbon” goals. This study developed a groove and tenon splicing technique for thick veneers, enabling infinite splicing of the length direction and the preparation of a large-size CLTV measuring 12 m (length) × 3.25 m (width) × 105 mm (thickness). The mechanical properties of CLTV were studied in relation to splice position, assembly pattern of grain directions, and layer combinations. The results showed that increasing the number of // layers (// or ⊥ indicates grain direction of layer parallel or perpendicular to the length direction of CLTV) and using high-level layers significantly improved the compressive strength and reduced the coefficient of variation of CLTV. In terms of bending properties, reasonable splice distribution, placing // layers away from the neutral axis, and elevating layer level dramatically enhanced CLTV performance. Furthermore, the study revealed the synergistic effect among these design elements. The effects of layer level and the number of // layers on mechanical properties varied depending on splice arrangement and assembly pattern of grain directions, highlighting the importance of efficient structural design and raw material selection. This study addresses the limitations of traditional cross-laminated timber in raw material selection and production efficiency. Through structural innovation, it offers a solution for physical design and performance regulation, enabling the application of larger CLTV in wood structures and presenting new ideas for using fast-growing wood to reduce construction emissions. Full article

Ride comfort is an important requirement that passenger rail vehicles must meet. Carbody–anti-bending system is a relatively new passive method to enhance the ride comfort in passenger rail vehicles with long and light carbody. The resonance frequency of the first bending mode (FBM) of such vehicle is within the most sensitive frequency range that affects ride comfort. Anti-bending bars consist of two bars that are mounted under the longitudinal beams of the carbody chassis using vertical supports. When the carbody bends, the anti-bending bars develop moments in the neutral axis of the carbody opposing the bending of the carbody. In this way, the carbody structure becomes stiffer and the resonance frequency of the FBM can be increased beyond the upper limit of the discomfort range of frequency, improving the ride comfort. The theoretical principle of this method has been demonstrated employing a passenger rail vehicle model that includes the carbody as a free–free Euler–Bernoulli beam and the anti-bending bars as longitudinal springs jointed to the vertical supports. Also, the method feasibility has been verified in the past using an experimental scale demonstrator system. In this paper, a new model of the carbody–anti-bending bar system is proposed by including three-directional elastic elements (vertical and longitudinal direction and rotation in the vertical–longitudinal plane) to model the fastening of the anti-bending bars to the supports and the vertical motion of the anti-bending bars modelled as free–free Euler–Bernoulli beams connected to the elastic elements of the fastening. In the longitudinal direction, the anti-bending bars work as springs connected to the longitudinal elastic elements of the fastening. The modal analysis method is applied to point out the basic properties of the frequency response functions (FRFs) of the carbody–anti-bending bars system, considering the bounce and FBMs of both the carbody and the anti-bending bars. A parametric study of the FRF of the carbody shows that the vertical stiffness of the fastening should be sufficiently high enough to eliminate the influence of the modes of the anti-bending bars upon the carbody response and to reduce the anti-bending bars vibration in the frequency range of interest. Longitudinal stiffness of the elastic elements of the fastening is critical to increase the bending resonance frequency of the carbody out of the sensitive range. Longer anti-bending bars can improve the capability of the anti-bending bars to increase the bending resonance without the risk of interference effects caused by the bounce and bending modes of the anti-bending bars. Full article

In addition to the traditional uses of plywood, such as furniture and construction, it is also widely used in areas that benefit from its special combination of strength and lightness, particularly as a construction material for the production of finishing elements of campervans and yachts. In light of the current need to reduce emissions of climate-damaging gases such as CO₂, the use of lightweight construction materials is very important. In recent years, hybrid structures made of carbon fibre-reinforced plastics (CFRPs) and metals have attracted much attention in many industries. In contrast to hybrid metal/carbon fibre composites, research relating to laminates consisting of CFRPs and wood-based materials shows less interest. This article analyses the hybrid laminate resulting from bonding a CFRP panel to plywood in terms of strength and performance using a three-point bending test, a static tensile test and a dynamic analysis. Knowledge of the dynamic characteristics of carbon fibre-reinforced plywood allows for the adoption of such cutting parameters that will help prevent the occurrence of self-excited vibrations in the cutting process. Therefore, in this work, it was decided to determine the effect of using CFRP laminate on both the static and dynamic stiffness of the structure. Most studies in this field concern improving the strength of the structure without analysing the dynamic properties. This article proposes a simple and user-friendly methodology for determining the damping of a sandwich-type system. The results of strength tests were used to determine the modulus of elasticity, modulus of rupture, the position of the neutral axis and the frequency domain characteristics of the laminate obtained. The results show that the use of a CFRP-reinforced plywood panel not only improves the visual aspect but also improves the strength properties of such a hybrid material. In the case of a CFRP-reinforced plywood panel, the value of tensile stresses decreased by sixteen-fold (from 1.95 N/mm² to 0.12 N/mm²), and the value of compressive stresses decreased by more than seven-fold (from 1.95 N/mm² to 0.27 N/mm²) compared to unreinforced plywood. Based on the stress occurring at the tensile and compressive sides of the CFRP-reinforced plywood sample surface during a cantilever bending text, it was found that the value of modulus of rupture decreased by three-fold and the value of the modulus of elasticity decreased by more than five-fold compared to the unreinforced plywood sample. A dynamic analysis allowed us to determine that the frequency of natural vibrations of the CFRP-reinforced plywood panel increased by about 33% (from 30 Hz to 40 Hz) compared to the beam made only of plywood. Full article

In this study, epoxy-based composites were fabricated using a layer-by-layer assembly technique, and their mechanical properties were systematically evaluated. The inclusion of cellulose nanocrystals led to variations in the mechanical properties of the composites. These modified properties were assessed through tensile and flexural tests, with each layer cast to enhance strength. Due to the inherent characteristics of epoxy, a single specimen was fabricated through chemical bonding, even post-curing. This approach demonstrated that a three-layer structure, developed using the layer-by-layer method, exhibited improved elastic and flexural moduli compared to a single-layer composite. This improvement aligns with theoretical predictions, which suggest that stiffness increases when stiffer materials are positioned farther from the neutral axis in a layered structure. Furthermore, numerical analysis validated changes in stress distribution across each layer. Consequently, this method enables the production of composites with superior mechanical properties while minimizing the quantity of cellulose nanocrystals required. Full article