Search Results (36)

Optimization of process parameters for manufacturing of individual surfaces and the product as a whole is one of the key tasks of technological preparation of production. Processing of individual design elements of the product is a structurally complex process, which is a clear sequence of actions characterized by a set of parameters. The effectiveness of the optimization process directly depends on the level of detail of the process under study and the optimal choice of targets and control parameters. Thus, for a single design element of the product, the control task is reduced to the structural and parametric optimization of its processing. For this purpose, it is necessary to develop a hierarchical model of structural and parametric optimization of the processing of individual design elements of the product. The paper presents a structural hierarchical model of the design element forming process, describing the sequence of actions and intermediate states of the object at different control levels. The model is based on the structural decomposition of the process and includes three levels: technological processing route, technological transition, and working stroke. For each level, theoretical-multiple models, vector optimization criteria, control parameters, and boundary conditions are defined. The article also demonstrates the application of the model on the example of optimization for the process of shaping a group of threaded holes, where the Pareto-optimization method was used to obtain optimal machining parameters that reduced the labor intensity with an acceptable increase in error and surface roughness. The paper presents the results of controlling the machining process of a group of threaded holes by means of structural optimization of the machining process route and parametric optimization of cutting parameters for each working stroke. Optimal parameters of the machining process for the investigated group of threaded holes are achieved by reducing the number of technological transitions within the technological route of machining, as well as optimizing the value of cutting speed set in the process of tapping with a tapsetter. Thus, as a result of the optimization, the total labor intensity of individual transitions decreased by 18.3%, with an increase in processing error by 12.1%, and deterioration of the roughness parameter by 13.2%, which satisfies the initial conditions of optimization. The obtained results prove the effectiveness of the developed hierarchical model of controlling the process of machining individual design elements of the product through structural and parametric optimization of its individual stages. Full article

In view of the application status and technical challenges of steel–wood composite joints in architecture, this paper proposes an innovative connection technology to solve issues such as susceptibility to pry-out at beam–column joints and low load-bearing capacity and to provide various reinforcement methods in order to meet the different structural requirements and economic benefits. By designing and manufacturing four groups of beam–column joint specimens with different reinforcement methods, including no reinforcement, structural adhesive and angle steel reinforcement, 4 mm thick steel sleeve reinforcement, and 6 mm thick steel sleeve reinforcement, monotonic loading tests and finite element simulations were carried out, respectively. This research found that unreinforced specimens and structural adhesive angle steel-reinforced joints exhibited obvious mortise and tenon compression deformation and, moreover, tenon pulling phenomena at load values of approximately 2 kN and 2.6 kN, respectively. However, the joint reinforced by a steel sleeve showed a significant improvement in the tenon pulling phenomenon and demonstrated excellent initial stiffness characteristics. The failure mode of the steel sleeve-reinforced joints is primarily characterized by the propagation of cracks at the edges of the steel plate and the tearing of the wood, but the overall structure remains intact. The initial rotational stiffness of the joints reinforced with angle steel and self-tapping screws, the joints reinforced with 4 mm thick steel sleeves, and the joints reinforced with 6 mm thick steel sleeves are 3.96, 6.99, and 13.62 times that of the pure wooden joints, while the ultimate bending moments are 1.97, 7.11, and 7.39 times, respectively. Using finite element software to simulate four groups of joints to observe their stress changes, the areas with high stress in the joints without sleeve reinforcement are mainly located at the upper and lower ends of the tenon, where the compressive stress at the upper edge of the tenon and the tensile stress at the lower flange are both distributed along the grain direction of the beam. The stress on the column sleeve of the joints reinforced with steel sleeves and bolts is relatively low, while the areas with high strain in the beam sleeve are mainly concentrated on the side with the welded stiffeners and its surroundings; the strain around the bolt holes is also quite noticeable. Full article

To achieve the assembled connection between dovetail profiled steel sheets and the boundary members in dovetail profiled steel concrete composite shear walls (DPSCWs), self-tapping screws were employed. Three DPSCW specimens connected with self-tapping screws were tested under combined axial and cyclic lateral loads to evaluate their hysteretic response, focusing on the influence of the number of self-tapping screws and the axial compression ratio. The self-tapping screw-connected DPSCWs exhibited a mixed failure mode, characterized by shear failure of the profiled steel sheets and compression-bending failure of multiple wall limbs divided by ribs on the web concrete. Except for slight deformation at the screw holes located on the profiled sheets at the corners of the wall, the connections exhibited minimal visible damage. The yield drift ratio of the DPSCW specimens in the test ranged from 1/286 to 1/225, and the ultimate drift ratio ranged from 1/63 to 1/94, both meeting the relevant deformation standards specified in the “Code for Seismic Design of Buildings. Increasing the number of self-tapping screws enhanced the development of local tensile fields on the profiled steel sheets, thereby improving the wall’s load-carrying, deformation, and energy dissipation capacities. However, increasing the axial compression ratio improved the initial stiffness of DPSCWs but reduced their load bearing and deformation capacity. Moreover, a design method for the self-tapping screw connections in DPSCWs was proposed. Full article

Objective: This study aimed to explore longitudinal relationships between neurophysiological biomarkers and upper limb motor function recovery in stroke patients, focusing on electroencephalography (EEG) and transcranial magnetic stimulation (TMS) metrics. Methods: This longitudinal cohort study analyzed neurophysiological, clinical, and demographic data from 102 stroke patients enrolled in the DEFINE cohort. We investigated the associations between baseline and post-intervention changes in the EEG theta/alpha ratio (TAR) and TMS metrics with upper limb motor functionality, assessed using the outcomes of five tests: the Fugl-Meyer Assessment (FMA), Handgrip Strength Test (HST), Pinch Strength Test (PST), Finger Tapping Test (FTT), and Nine-Hole Peg Test (9HPT). Results: Our multivariate models identified that a higher baseline TAR in the lesioned hemisphere was consistently associated with poorer motor outcomes across all five assessments. Conversely, a higher improvement in the TAR was positively associated with improvements in FMA and 9HPT. Additionally, an increased TMS motor-evoked potential (MEP) amplitude in the non-lesioned hemisphere correlated with greater FMA-diff, while a lower TMS Short Intracortical Inhibition (SICI) in the non-lesioned hemisphere was linked to better PST improvements. These findings suggest the potential of the TAR and TMS metrics as biomarkers for predicting motor recovery in stroke patients. Conclusion: Our findings highlight the significance of the TAR in the lesioned hemisphere as a predictor of motor function recovery post-stroke and also a potential signature for compensatory oscillations. The observed relationships between the TAR and motor improvements, as well as the associations with TMS metrics, underscore the potential of these neurophysiological measures in guiding personalized rehabilitation strategies for stroke patients. Full article

Prefabricated wood construction relies heavily on efficient material handling, yet rigging system design for floor panels remains understudied. This study introduces a novel rigging device that attaches to prefabricated wood I-joist floor panels using self-tapping screws, avoiding potential damage caused by predrilled holes in the sheathing panels and framing members. To establish allowable lifting capacities and optimal installation practices, comprehensive withdrawal tests were conducted on 114-floor panel specimens. Factors influencing withdrawal capacity, such as anchor plate placements, flange materials and width, screw type and quantity, and sheathing panel thickness, were systematically evaluated. Results indicate that withdrawal capacity does not scale linearly with screw quantity and that anchor plates with eight screws centered on the flange enhance performance by up to 20% compared to four-screw configurations. Unexpectedly, thinner sheathing panels yielded higher capacities, potentially due to increased screw penetration depth in the joist flange. In addition, anchor plate orientation, flange width, and flange materials also impact capacity. These findings provide essential data for designing reliable and efficient rigging systems in prefabricated wood construction. Full article

The efficient separation of photogenerated charge carriers and strong oxidizing properties can improve photocatalytic performance. Here, we combine the construction of a tightly connected S-scheme heterojunction with the exposure of an active crystal plane to prepare g-C₃N₄/BiOBr for the degradation of high-concentration organic pollutants. This strategy effectively improves the separation efficiency of photogenerated carriers and the number of active sites. Notably, the synthesized g-C₃N₄/BiOBr displays excellent photocatalytic degradation activity towards various organic pollutants, including methylene blue (MB, 90.8%), congo red (CR, 99.2%), and tetracycline (TC, 89%). Furthermore, the photocatalytic degradation performance of g-C₃N₄/BiOBr for MB maintains 80% efficiency under natural water quality (tap water, lake water, river water), and a wide pH range (pH = 4–10). Its excellent photocatalytic activity is attributed to the tight connection between g-C₃N₄ and BiOBr in the S-scheme heterojunction interface, as well as the exposure of highly active (001) crystal planes. These improve the efficiency of the separation of photogenerated carriers, and maintain their strong oxidation capability. This work presents a simple approach to improving the separation of electrons and holes by tightly combining two components within a heterojunction. Full article

Bohai X oilfield has reached the extra-high water cut stage of more than 95%, dominated by the bottom water reservoir. The oilfield mainly adopts horizontal-well exploitation, with the characteristics of high difficulty and low success rate for well water plugging. To solve the above problem, the segmented production technology of horizontal wells was developed to guide oilfield applications and tap their potential. In the segmented design stage, the horizontal section is objectively segmented by drilling condition analysis, optimally based on drilling through interlayers or permeability discrepancy formation, simultaneously combined with the numerical simulation method. When implementing measures, annulus chemical packer materials are squeezed between segments to effectively inhibit the fluid flow between the open hole and the sand-packing screen pipe. Moreover, the packers are used to seal between segments to effectively restrain the flow between the screen and the central tube, achieving the establishment of compartments. In the production process, the valve switch on the central tube can be independently controlled by a remotely adjustable method to achieve optimal production. This segmented production technology was successfully tested for the first time in Bohai oilfield. Up to now, a total of six compartment measures have been implemented, remarkably decreasing water cut and increasing oil production for horizontal wells in the bottom water reservoir. This method does not require water testing, and the optimal production section can be chosen through segmented independent production, greatly improving the success rate of water-plugging measures for horizontal wells. This technology opens up a new mode for the efficient development of horizontal wells in bottom water reservoirs and is planned to be widely promoted and applied in similar oilfields. Full article

This research successfully synthesized SnO₂@ZnIn₂S₄ composites for photocatalytic tap water splitting using a rapid two-step microwave-assisted synthesis method. This study investigated the impact of incorporating a fixed quantity of SnO₂ nanoparticles and combining them with various materials to form composites, aiming to enhance photocatalytic hydrogen production. Additionally, different weights of SnO₂ nanoparticles were added to the ZnIn₂S₄ reaction precursor to prepare SnO₂@ZnIn₂S₄ composites for photocatalytic hydrogen production. Notably, the photocatalytic efficiency of SnO₂@ZnIn₂S₄ composites is substantially higher than that of pure SnO₂ nanoparticles and ZnIn₂S₄ nanosheets: 17.9-fold and 6.3-fold, respectively. The enhancement is credited to the successful use of visible light and the facilitation of electron transfer across the heterojunction, leading to the efficient dissociation of electron–hole pairs. Additionally, evaluations of recyclability demonstrated the remarkable longevity of SnO₂@ZnIn₂S₄ composites, maintaining high levels of photocatalytic hydrogen production over eight cycles without significant efficiency loss, indicating their impressive durability. This investigation presents a promising strategy for crafting and producing environmentally sustainable SnO₂@ZnIn₂S₄ composites with prospective implementations in photocatalytic hydrogen generation. Full article

The finger tapping test (FTT) is a tool to evaluate the motor performance of the hand and fingers and eye-hand coordination with applicability in people with multiple sclerosis (pwMS). The aim of this study was to evaluate the intra- and inter-rater reliability of the TappingPro^® mobile app and the construct validity between this app and validated clinical scales for motor performance in healthy subjects and pwMS. 42 healthy subjects (mean age 25.05) and 13 pwMS (mean age 51.69, EDSS between 3 and 7.5E) participated. FTT was performed with the TappingPro^® mobile app. All participants were examined twice, with a one-week interval between the two appointments. For the analysis of construct validity, the Jamar^® hydraulic hand dynamometer, Box and Blocks Test (BBT), and Nine Hole Peg Test (NHPT) were used. The intra-rater reliability showed a good correlation (Intraclass Correlation Coefficient, ICC > 0.787) for both upper limbs and both times of FTT for healthy subjects, and an excellent correlation (ICC > 0.956) for upper limbs and both times of FTT for pwMS. The ICC for the inter-rater reliability was good (ICC = 0.869) for the non-dominant upper limb in the FTT 10 s of the healthy subjects, and excellent (ICC > 0.904) for all the other measurements of the healthy subjects and pwMS. However, the Bland–Altman plots showed disagreement between observers and measurements that should be considered in the interpretation of clinical evaluations. The correlation analysis for healthy subjects showed poor associations between all variables, except for the association between hand grip strength and the FTT 60 s in the non-dominant upper limb, which had a moderate coefficient. For pwMS, there were moderate to excellent associations between BBT and the NHPT and FTT for both upper limbs. The correlations between hand grip strength and FFT were poor. This mobile app could be a useful and low-cost assessment tool in pwMS, allowing a simple evaluation and follow-up that has excellent correlation with clinical scales validated in this pathology. Full article

This work investigates micro-electro discharge machining (EDM) performance involving deionized and tap water. The chosen machining regime was semi-finishing, where open voltage (from 100 to 130 V) and current values (5–10 A) were applied using a 0.5 µs pulse-on time and a frequency of 150 kHz, i.e., a duty cycle of 25%. First, numerical analyses were performed via COMSOL Multiphysics and used to estimate the plasma channel distribution and melted material, varying the current, sparking gap, electrical conductivity, and permittivity of the two fluids. Then, experimentally, the micro-EDM of holes and channels in hardened thin steel plates were replicated three times for each considered fluid. The material removal rate (MRR), tool wear ratio (TWR), radius overcut, and surface roughness were plotted as a function of open voltage and electrical conductivity. The study proves that as voltage and current increase, the MRR and TWR decrease with electrical conductivity. Nonetheless, for higher electrical conductivity (tap water), the process did not proceed for lower open voltages and currents, and the radius overcut was reduced, contrary to what is commonly acknowledged. Finally, the crater morphology and size were evaluated using a confocal microscope and compared to simulated outcomes. Full article

Due to the advantages of a short cycle, low investment and low energy consumption per ton of steel, short-process electric furnace steelmaking is about to welcome a golden period of rapid development in China. During the operation of the electric furnace, a large amount of smoke and dust is generated. Most studies focus on organized emissions, and the impact of unorganized emissions in workshops on the environment cannot be ignored. This paper evaluates the thermal environment in the electric furnace steelmaking workshop based on the analytic hierarchy process and obtains the influence weight of the fugitive emission location. The mass concentration of dust at each measuring point increased by 1.17 mg/m³ on average, and the concentration of unorganized emission dust near the outlet was 23.572 mg/m³. The numerical simulation calculation model is established by the CFD method, a fixed initial jet velocity is set, the initial velocity of the ladle soot plume is changed, and the inclination angle, arrangement height and dust removal air volume of the dust hood are respectively adjusted in different tapping periods. The impact of simulation on the efficiency of dust collection for different dust removal hood configurations was investigated, considering variations in inclination angle, arrangement height and dust removal airflow. The optimal structural parameters for the dust removal hood were determined to be an inclination angle of 60° and an arrangement height of 2.4 m, and an optimal dust removal airflow was determined to be 110,000 m³/h. This study provides a theoretical foundation for engineering practice. Full article

Water with a high concentration of oxygen is needed for the aquaculture industry in Japan. In the current study, the pressurized dissolution method was employed to generate high-concentration oxygenated water (HCOW) by producing oxygen nanobubbles in the water. In order to investigate factors such as temperature, geometric conditions, and their influence on the oxygen concentration, a special nanobubble generator was improved by changing the number and the diameter of the holes of the perforated plate in this study. Then, an experimental system where oxygen and water were separately introduced inside the proposed nanobubble generator was designed. The dissolved oxygen concentration was measured under different conditions. Finally, the produced HCOW was used to cultivate a mini-sunflower. Through a series of experiments, it was found that with the improved perforated plate, the dissolved oxygen concentration was increased and the nanobubble generator reached the saturation state quickly, while the mini-sunflower cultivated with the HCOW appeared to grow larger than that with tap water. Full article

The aerodynamics of a high-speed low-pressure turbine (LPT) cascade were investigated under steady and unsteady inlet flows. The tests were performed at outlet Mach (M) and Reynolds numbers ($Re$) of $0.90$ and 70k, respectively. Unsteady wakes were simulated by means of a wake generator equipped with bars. A bar reduced frequency ($f^{+}$) of ∼0.95 was used for the unsteady case. The inlet flow field was characterized in terms of the total pressure profile and incidence. The blade aerodynamics at midspan and the secondary flow region were investigated by means of pneumatic taps and hot-film sensors. The latter provided a novel view into the impact of the secondary flows on the heat transfer topology on the blade suction side (SS). The cascade performance was quantified in terms of the outlet flow angle and losses by means of a directional multi-hole probe. The results report the phase-averaged impact of unsteady wakes on the secondary flow structures in an open test case high-speed LPT geometry. Full article

Degradation of pharmaceuticals in water by TiO₂ photocatalysis often suffers from low efficiency due to low activity and mass transfer limitation. In this work, diclofenac removal in tap water was performed by photocatalysis on TiO₂ nanotube growth on Ti mesh substrate assisted by ozone (O₃), which was generated from a hole-arrayed boron-doped diamond (HABDD) film electrode. The vertically oriented TiO₂ nanotubes were used as the heterogeneous photocatalyst. The HABDD, as a self-standing diamond electrode, was designed and custom-made by MWCVD technology. The microstructures and crystalline of the TiO₂ nanotubes and HABDD were characterized by a scanning electronic micrograph (SEM) and X-ray diffraction (XRD). Unlike other ozone generation methods, direct generation of ozone in the flowing water was applied in the photocatalysis process, and its effect was discussed. The diclofenac removal performance of the electrochemical-photocatalytic system was studied depending on O₃ generation efficiency, flowing rate, and the initial diclofenac concentration. The enhanced degradation effect from O₃ molecules on TiO₂ photocatalysis was attributed to the larger active surface area, the increased photo-generated charge separation rate, and the contact area of O₃. The degradation efficiency in the combined electrochemical-photocatalytic TiO₂/O₃/UV system was higher than that of the O₃/UV and TiO₂/UV routes individually. Furthermore, a theoretical calculation was used to analyze the TiO₂/O₃ interface in aqueous media in terms of the final energy. This system created an almost in situ feeding channel of oxidants in the TiO₂ photocatalysis process, thus increasing photocatalytic efficiency. This synergetic system is promising in the treatment of pharmaceuticals in water. Full article

The formulation of the CFD-DEM model, CD-MELT, is established in this study to include three-phase non-isothermal processes with simultaneous combustion and melting for gasification simulations. To demonstrate the model capability, CD-MELT is used to assess the need for slag recycling for the non-isothermal melting of municipal solid wastes (MSW) in a prototype waste-to-energy research facility. The simulation encompasses the full fixed-bed slagging gasification process, including chemical reactions and melting of MSW and slag. In order to assess the need for slag recycling, comparisons are made for the two cases of with and without, in terms of the slag mass, liquid slag volume fraction, exit gas composition, and temperature distribution in the gasifier. The prediction results enable the tracking of liquid molten slag as it permeates through the solids-packed bed for the first time in the literature as far as we are aware, which is crucial to address design considerations such as distribution of bed temperature and optimal location for slag-tap holes at the bottom, as well as potential slag clogging within the porous media. The model also predicts an uneven and intermittent slag permeation through the packed bed without the recycling, and provides a plausible explanation for the operators’ experience of why slag recycling is important for process stability. Finally, the predicted slag outlet temperature using the proposed CFD approach also agrees well with the measurement data published in an earlier case study for the same facility. Full article