Search Results (18)

The use of short cylinders of recycled aggregate concrete (RAC) reinforced with basalt fiber-reinforced polymer (BFRP) circumferential strips and polyvinyl chloride (PVC) tubes has been proven effective in previous studies. However, BFRP circumferential strips are cumbersome to install and do not ensure the integrity of the BFRP strips. Therefore, this study investigates axial compression experiments on RAC short cylinders reinforced with BFRP spiral strips and PVC tubes. A combination of experimental studies, finite element simulations, and theoretical analyses revealed that the winding angle and spacing of BFRP strips significantly affect the load-bearing capacity and ductility of the restrained specimens. Additionally, an improved strength model was developed based on an existing model. When evaluated using both computational and experimental results, the equations generated in this study showed an average error of less than 10%. The findings indicate that the composite structure provides effective reinforcement and offers valuable reference information for practical applications. Full article

Background: This study evaluated the outcomes of sutureless small incision Descemet’s Stripping Automated Endothelial Keratoplasty (DSAEK-SI) for treating corneal endothelial decompensation. Methods and Analysis: This retrospective study reviewed patients with corneal endothelial decompensation who underwent DSAEK-SI between January 2018 and June 2021 at the Vietnam National Eye Hospital. All patients were followed for at least one year postoperatively. The endothelial graft was inserted into the anterior chamber through a 2.8 mm main corneal incision using a Busin glide. The normal pressure air tamponade of the anterior chamber was applied to attach the graft to the recipient bed. The small incision required no sutures, and no need to remove part of the air from the anterior chamber. This ensured that the surgery ended immediately after the air tamponade, without having to wait for 15 min like with regular DSAEK. The patients were instructed to lie supine for at least 6 h postoperatively. Patients with cataracts underwent combined phacoemulsification and intraocular lens implantation with DSAEK-SI. Results: Sixty eyes from sixty patients were enrolled. The success rate of the surgery was 93.3%. Postoperatively, the best spectacle-corrected visual acuity (BSCVA) improved from 20/3600 to 20/400 at discharge and reached 20/100 at 12 months. Mild astigmatism (0.5D to 2D) was observed in 91.8% of patients, with a mean cylinder of 0.9 ± 0.4D at 12 months. The endothelial cell loss rate after 12 months was 34.6 ± 16%. No graft dislocations or detachments were recorded. Conclusions: The sutureless DSAEK-SI technique with a 2.8 mm incision is a modified technique that achieves high success rates and potentially reduces surgical manipulation and complications. Full article

Microalgae cultivation is a promising approach for sustainable CO₂ fixation. This work describes the optimization of a laboratory-scale experimental model for microalgae cultivation under CO₂ supplementation. The experimental model was developed using a stirred clear glass reactor, white LED strips, connection system caps with three ports, tubes, valves, regulators, and N₂-CO₂ compressed gas cylinder. Three microalgae strains were used: Raphidocelis subcapitata ATCC22662, Desmodesmus communis NIVA-CHL 7, and Chlorella sorokiniana NIVA-CHL 176. The appropriate medium for cultivation of each of these strains was selected. The optimized experimental model demonstrated the positive influence of CO₂ supplementation on microalgae growth, particularly for Chlorella sorokiniana. Full article

The vibration of the vertical system of a cold rolling mill is a major concern for factory production. In factory production, it is found that the thickness control system with dynamic stiffness compensation of the rolling mill has a significant impact on the rolling mill vibration. In this work, a mechanical hydraulic coupling vibration model of a cold rolling mill with a thickness control system with dynamic stiffness compensation was established. MATLAB/Simulink was used to simulate and analyze the vibration response characteristics of the mechanical structure of the rolling mill and mechanical hydraulic coupling system considering the dynamic stiffness compensation control mode and position control mode of the upper cylinder. We found that the control system changed the vibration response of the mechanical structure, and different control modes have different effects on the vibration response curve. When the rolling mill works in the vibration area, the thickness difference at the strip steel outlet would be larger. Considering the rolling mill vibration and strip surface quality, the excitation of the strip inlet thickness can be achieved by adjusting the dynamic stiffness compensation system and changing the rolling speed reasonably to achieve good vibration suppression and control effects. Full article

The development of a reusable and low-cost urine glucose sensor can benefit the screening and control of diabetes mellitus. This study focused on the feasibility of employing microbial fuel cells (MFC) as a selective glucose sensor for continuous monitoring of glucose levels in human urine. Using MFC technology, a novel cylinder sensor (CS) was developed. It had a quick response time (100 s), a large detection range (0.3–5 mM), and excellent accuracy. More importantly, the CS could last for up to 5 months. The selectivity of the CS was validated by both synthetic and actual diabetes-negative urine samples. It was found that the CS’s selectivity could be significantly enhanced by adjusting the concentration of the culture’s organic matter. The CS results were comparable to those of a commercial glucose meter (recovery ranged from 93.6% to 127.9%) when the diabetes-positive urine samples were tested. Due to the multiple advantages of high stability, low cost, and high sensitivity over urine test strips, the CS provides a novel and reliable approach for continuous monitoring of urine glucose, which will benefit diabetes assessment and control. Full article

In high-voltage cables, because of the close fit of their internal structures, interface pressure is generated between conductor and insulator, which affects the performance of the cable. Studies on the calculation and testing of the interfacial pressure of cable conductors are scarce because of the lack of a unified formula and the difficulty of direct measurement. As such, in this study, we devised two methods for calculating and measuring the interface pressure of cable conductors. In the first, we used two physical experimental methods. We used the friction between cable components to perform the calculation and create an experimental method for determining cable conductor interface pressure; on the basis of the equation of the pressure inside and outside a thick-walled cylinder using elasticity mechanics, we calculated the interface pressure on the basis of the measurement of the strain state of the inner and outer diameters of each layer of the cable under different assembly and stripping conditions. We verified the effectiveness of the methods through physical tests and simulations using a YJLW03 1 × 1200 high-voltage cable. Then, we used simulation software ANSYS and SolidWorks to calculate the interface pressure. With different simulation settings, we obtained results regarding interface pressure. Lastly, these simulated values were individually compared with two physical tests, and the error was calculated. Results obtained in the ANSYS environment showed that interface pressure values determined by the geometric interference normal stress, geometric interference pressure, contact interference normal stress, and contact interference pressure methods were 39.75, 36.84, 5.76, and 36.57 MPa, respectively. In SolidWorks software, we used the contact-stress and X-axis normal stress methods. Results were all 37.36 MPa. Then, simulation results and experimental results were compared, and error was calculated. The comparison showed that the X-axis orthogonal stress method was the most accurate. Errors between the X-axis orthogonal stress method and the two physical experiments were 1.5% and 0.48%. Through the above simulation and physical experiments, we determined the interface pressure between conductors and insulators in a high-voltage power cable. We obtained the cable interface pressure value through two kinds of physical experiments, and these two methods were clearly reliable. Simulation experiments showed that using SolidWorks software to simulate this problem obtained better results. Research results provide technical support and reference for the calculation and measurement of cable interface pressure and the optimization of cable performance. Full article

Cavitation characteristics in the wake of a circular cylinder, which contains multiscale vortices, are numerically investigated via Large Eddy Simulation (LES) in this paper. The Reynolds number is 9500 based on the inlet velocity, the cylinder diameter and the kinematic viscosity of the noncavitation liquid. The Schneer–Sauer (SS) model is applied to cavitation simulation because it is more sensitive to vapor–liquid two-phase volume fraction than the Zwart–Gerber–Belamri (ZGB) model, according to theoretical analyses. The wake is quasiperiodic, with an approximate frequency of 0.2. It is found that the cavitation of vortices could inhibit the vortex shedding. Besides, the mutual aggregation of small-scale vortices in the vortex system or the continuous stripping of small-scale vortices at the edge of large-scale vortices could induce the merging or splitting of cavities in the wake. Full article

Biphasic drug delivery systems are used for quick release of a specific amount of drug for immediate amelioration of a patient’s state, followed by sustained release, to avoid repeated administration. This type of delivery is often necessary for pain management and the treatment of many pathologies, such as migraines, hypertension, and insomnia. In this work, we propose a novel architecture of a biphasic release media that does not need the rapidly disintegrating layer and that allows for easily setting the sustained release rate. A drug-containing capsule is made by rolling up a thermally crosslinked gelatin strip on which drug reservoirs are formed by casting. The quick-release reservoir (QRR) is placed at the strip’s extremity, from which the rolling starts, while the sustained-release reservoir (SRR) is formed in the middle part of the strip. The strip is rolled around a cylinder that is a few millimeters wide, which is removed after rolling. The roll is stabilized by transglutaminase-catalyzed crosslinking of the consecutive shells. A biphasic release is successfully demonstrated with the use of model fluorescent drugs for single-dye and double-dye systems in phosphate-buffered saline (PBS) solution with pH = 7.4. In vitro, the drug from the QRR, placed at the walls of the cavity of the roll, is released immediately upon the capsule’s contact with the PBS solution. The drug from the SRR, embedded between the roll’s layers, diffuses steadily, with the lag time defined by the radial position of the reservoir. Full article

The aim of this study is to develop a mathematical model for the prediction of compression pressure based on fabric parameters, such as engineering stress, engineering strain and engineering modulus of elasticity. Four knitted compression fabrics with different fibrous compositions and knit structures were used. Rectangular-cut strips were employed for the force–elongation characterization of the fabrics. The experimental pressure values between the fabric and rigid cylinder were assessed using a Picopress pressure measuring device. The mechanical and physical parameters of the fabric that influence the interface pressure, such as strain, elasticity modulus/stress and thickness, were determined and integrated into Laplace’s law. A good correlation was observed between the experimental and calculated pressure values for all combinations of fabrics, mounted with variable tension on the cylinder. Over the considered range of pressures, the difference between the two datasets was generally less than 0.5 mmHg. The effect of washing after five, ten and fifteen washing cycles on the fabric–cylinder interface pressure was found to be significant. Full article

The synergistic control of resistance reduction and sealing poses challenges to enhancing the rapid dynamic response ability of servo hydraulic cylinders; the key to solving this problem is effectively controlling the sealing gap value. In this study, a micro-variation between the hydraulic cylinder and the piston based on the disadvantage of conventional seals, constant gap seals, and lip gap seals was constructed; MSMA assist support blocks were designed on the piston to form a gap seal strip; then, the sealing gap value could be changed by controlling the magnetic field intensity. Simultaneously, the effects of magnetic field strength, parts-manufacturing precision, temperature, and hysteresis on the micro-variation in the MSMA were analyzed, and effective solutions were proposed. Finally, experiments on the magnetic field, temperature, and hysteresis were conducted by the measurement system. The results showed that the variable value of the sealing gap with the MSMA is feasible under ideal conditions, and can effectively change the amount of MSMA expansion by controlling the magnetic field strength, temperature, preload, etc., and then change the amount of the sealing gap of the hydraulic cylinder. This is the key to achieving friction and sealing control, which plays a crucial and active role in improving the efficiency of hydraulic systems. However, the impact of hysteresis effects cannot be ignored, which will be the main problem to be solved in the future. Full article

We describe a method for constructing developable bands with N ≥ 3 half twists. Each band is formed by threading a flat rectangular strip through a scaffold made from identical circular cylinders and smoothly connecting its short ends. The N cylinders in a scaffold are arranged with N-fold rotational symmetry. The number of half twists in a band is equal to the number N of cylinders in its scaffold and each band inherits the symmetry of its scaffold. Each scaffold admits a family of bands of the same length but variable width up to a maximum value determined by the features of the scaffold. Apart from orientable and nonorientable unknots, our method allows for the construction of bands with the topology of torus knots. We detail the geometric properties of the construction, discuss certain fundamental restrictions that must be met to ensure constructability, and calculate the elastic bending energy of each band. The rotational symmetry underlying the construction is essential for obtaining the presented bands, as the general non-symmetric problem is even more complex and has not yet been investigated. The bands and their corresponding scaffolds can be used as structural elements in practical applications, one of which we describe and analyze. The construction serves as a basis for a general framework for building a large variety of scaffolds and the corresponding unstretchable bands. Together, these assemblies can be used in architectural, interior, and machine design. They also open new avenues for the layout of conveyor belts in factories, airports, and other settings. Full article

The rapid evolution of materials and manufacturing processes, driven by global competition and new safety and environmental regulations has had an impact on automotive structures (Body In White; BIW) manufacturing. The need for lighter vehicles, with more equipment, that are safer and eco-friendly at the same time, relates to the entire life cycle of the car. Car and steelmakers agree that weight reduction is possible, and the solution involves the use of new advanced high-strength steels. Thinner and stronger materials lead to higher demands on stamping, the most used manufacturing in BIW parts. The use of advanced high-strength steels raises new challenges, especially concerning the lubrication between the die and the sheet. To study the lubrication conditions of the stamping process, a sheet metal forming a simulator was developed. The simulator consists of two cylinders that pull the strip of steel and a pin in between. The angle between the cylinders can be adjusted from 0 to 90 degrees, which allows analysis of the effect of the stamping angle. The pull force and velocity can be set and measured, and the peripheric pin velocity, the strain, and the strain velocity can be measured as well. In this work, the tribological properties of Dual-Phase 600 stainless steel using different processing conditions have been analyzed. To this end, a factorial experiments design with twelve parameters that compare the behavior of different angles and diameters was run. The results showed that the friction coefficient increases by increasing the bending angle and decreases with pin diameter. Full article

At the 1998 Nagano Winter Olympic Games, zigzag tape was introduced on the race suit lower legs and cap of speed skaters. Application of these zigzag devices on live skaters and cylinders in the wind tunnel showed large improvements in the aerodynamic drag. These wind-tunnel results were unfortunately not widely published, and the impact of the zigzag strips in a real skating environment was never established. This paper aims to show the background of the application of the zigzag tape and to establish the impact it may have had on speed-skating performance. From comparisons of 5000 m races just before, during and just after the Nagano Olympics and an analysis of historic world record data of the 1500 m men’s speed skating, the impact of the zigzag tape turbulators on average lap times on 1500 and 5000 m races is calculated to be about 0.5 s. Full article

The finite volume method, based on the dynamic mesh method, is used to investigate the transient viscous incompressible flow around an impulsively and translationally started cylinder with strips. The strips of different shapes are installed at different locations on the surface of the cylinder. The main purpose of this paper is to investigate the influence of the locations and shapes of strips on the flow caused by boundary motion. The present solutions agree well with the experimental results reported in literature. Six placement angles of strips were selected: 0°, 20°, 60°, 90°, 120° and 150°. The development of wake shows some new phenomena with different strip locations, and the significant difference appears at α = 90°. The vortex intensity is much larger than that of other locations. On the other hand, four shapes of strips were selected: arc, triangle, rectangle and trapezoid. The rectangular strips had the greatest influence on the drag coefficient and the maximum of the drag coefficient increased from 0.4 to 2.8, compared with the smooth cylinder. The maximum of negative velocity had the most significant change when the shape of strip is arc, increasing by 34% compared with the smooth cylinder, at T = 3. Full article

The rolling mill with hydraulic system is widely used in the production of strip steel. For the problem of vertical vibration of the rolling mill, the effects of different equivalent damping coefficient, leakage coefficient, and proportional coefficient of the controller on the hydraulic screw down system of the rolling mill are studied, respectively. First, a vertical vibration model of a hydraulic screw down system was established, considering the nonlinear friction and parameter uncertainty of the press cylinder. Second, the correlation between different equivalent damping coefficient, internal leakage coefficient, proportional coefficient, vertical vibration was analyzed. The simulation results show that, in the closed-loop state, when Proportional-Integral-Derivative (PID) controller parameters are fixed, due to the change of the equivalent damping coefficient and internal leakage coefficient, the system will have parameter uncertainty, which may lead to the failure of the PID controller and the vertical vibration of the system. This study has theoretical and practical significance for analyzing the mechanism of vertical vibration of the rolling mill. Full article