Search Results (27)

This study innovatively proposes a pipeline-type pneumatic lift sediment removal device for cleaning pollutants at the bottom of fish breeding tanks and conducts hydrodynamic characteristic analysis on its core component, the pneumatic lift pipeline structure, which consists of a horizontal circular tube with multiple micro-orifices at the bottom and an upward-inclined circular tube. The pipeline has an inner diameter of 20 mm and a vertical length of 1.2 m, with the orifice at one end of the horizontal tube connected to the gas supply line. During operation, compressed gas enters the horizontal tube, generating negative liquid pressure that draws solid–liquid mixtures from the tank bottom into the pipeline, while buoyant forces propel the gas–liquid–solid mixture upward for discharge through the outlet. Under a constant gas flow rate, numerical simulations investigated efficiency variations through three operational scenarios: ① different pipeline orifice diameters, ② varying orifice quantities and spacings, and ③ adjustable pipeline bottom clearance heights. The results indicate that in scenario ①, an orifice diameter of 4 mm demonstrated optimal efficiency; in scenario ②, the eight-orifice configuration achieved peak efficiency; and scenario ③ showed that the proper adjustment of the bottom clearance height enhances pneumatic efficiency, with maximum efficiency observed at a clearance of 10 mm between sediment suction pipe and tank bottom. Full article

Health care workers performing radiography on patients in hospitals typically wear aprons for radiation protection. Protective properties are achieved through a combination of shielding materials and polymers. Various shielding materials are mixed with polymers to prepare composite materials. Numerous methods have been devised to design and alter the composition of these materials to improve the shielding performance of aprons. In this study, the shielding performance was analyzed based on the arrangement of shielding materials, the composition of materials (mixed or single), and the fabrication design of the shielding sheets. Various shielding sheets were created using different arrangements of tungsten oxide, bismuth oxide, and barium sulfate, and their shielding efficacy was compared. The atomic number and density of the shielding material directly affect the shielding property. The effectiveness of the composite sheet increased by more than 5% when positioned close to the X-ray tube. Sheets fabricated from materials separated by type, rather than mixed, exhibited a greater X-ray shielding effectiveness because of their layered structure. Therefore, structural design considerations such as linings, outer layers, and inner layers of protective sheets should be considered for effective shielding in medical institutions. Full article

Testing was carried out in this study to evaluate the friction and wear performance of 45# steel inner liner pipes with cladding, along with four different types of centralizing materials (45# steel, nylon, polytetrafluoroethylene (PTFE), and surface alloy coating) in oil field conditions. Under dry-friction conditions, the coefficients of friction and rates of wear are significantly higher than their counterparts in aqueous solutions. This is attributed to the lubricating effect provided by the aqueous solution, which reduces direct friction between contact surfaces, thereby lowering wear. As the degree of mineralization in the aqueous solution increases, the coefficient of friction tends to decrease, indicating that an elevated level of mineralization enhances the lubricating properties of the aqueous solution. The wear pattern in an aqueous solution is similar to that in dry-friction conditions under different loads, but with a lower friction coefficient and wear rate. The coating has played an important role in protecting the wear process of 45# steel, and the friction coefficient and wear rate of tubing materials under various environmental media have been significantly reduced. In terms of test load, taking into account the friction coefficient and wear rate, the suggested order for centralizing materials for lining oil pipes with the surface alloy coating is as follows: (i) surface alloy coating, (ii) nylon, (iii) PTFE, and (iv) 45# steel. Full article

Despite advancements in the sensitivity and performance of analytical instruments, sample preparation remains a bottleneck in the analytical process. Currently, solid-phase extraction is more widely used than traditional organic solvent extraction due to its ease of use and lower solvent requirements. Moreover, various microextraction techniques such as micro solid-phase extraction, dispersive micro solid-phase extraction, solid-phase microextraction, stir bar sorptive extraction, liquid-phase microextraction, and magnetic bead extraction have been developed to minimize sample size, reduce solvent usage, and enable automation. Among these, in-tube solid-phase microextraction (IT-SPME) using capillaries as extraction devices has gained attention as an advanced “green extraction technique” that combines miniaturization, on-line automation, and reduced solvent consumption. Capillary tubes in IT-SPME are categorized into configurations: inner-wall-coated, particle-packed, fiber-packed, and rod monolith, operating either in a draw/eject system or a flow-through system. Additionally, the developments of novel adsorbents such as monoliths, ionic liquids, restricted-access materials, molecularly imprinted polymers (MIPs), graphene, carbon nanotubes, inorganic nanoparticles, and organometallic frameworks have improved extraction efficiency and selectivity. MIPs, in particular, are stable, custom-made polymers with molecular recognition capabilities formed during synthesis, making them exceptional “smart adsorbents” for selective sample preparation. The MIP fabrication process involves three main stages: pre-arrangement for recognition capability, polymerization, and template removal. After forming the template-monomer complex, polymerization creates a polymer network where the template molecules are anchored, and the final step involves removing the template to produce an MIP with cavities complementary to the template molecules. This review is the first paper to focus on advanced MIP-based IT-SPME, which integrates the selectivity of MIPs into efficient IT-SPME, and summarizes its recent developments and applications. Full article

Bimetallic lined pipe (BLP) has been increasingly used in offshore and subsea oil and gas structures, but how to identify the invisible inner defects such as liner wall thinning and interface debonding is a challenge for future development. A nondestructive testing (NDT) method based on pulsed eddy current testing (PECT) has been proposed to face these difficulties. The inspection of the BLP specimen (AISI1020 base tube and SS304 liner) is implemented from outside of the pipe by using a transmitter–receiver-type PECT probe consisting of two induction coils. By simplifying the BLP specimen to stratified conductive plates, the electromagnetic field interaction between the PECT probe and specimen is analytically modeled, and the probe inspection signals due to liner wall thinning and interface debonding are calculated. In order to highlight the weak response (in microvolts) from the liner, the inspection signals are subtracted by the signal, which is calculated in the case of only having a base tube, yielding differential PECT signals. The peak voltage of the differential signal is selected to characterize the liner wall thinning and interface debonding due to its distinguishable and linear variation. Experiment verification is also carried out on a double-walled specimen simulated by a combination of a Q235 casing pipe and SS304 tubes of different sizes. The experimental results basically agree with the analytical predictions. The peak value of the PECT signal has an ascending and descending variation with the increase in the remaining liner wall thickness and debonding gap, respectively, while the negative peak value shows opposite changes. The peak value exhibits a larger sensitivity than the negative peak value. The proposed method shows potential promise in practical applications for the evaluation of the inner defects in BLP lines. Full article

Kaplan turbines are widely utilized in low-head and large flow power stations. This paper employs Computational Fluid Dynamics (CFD) to complete numerical calculations of the full flow channel under different blade angles and various guide vane openings, based on 25 off-cam experimental working conditions. The internal flow characteristics of the runner blade and draft tube are analyzed, and a discriminant number for quantitatively assessing the flow uniformity of the draft tube is proposed. The results indicate that low-frequency and high-amplitude pressure pulsations occur on the high- and low-pressure edge of the blade when the opening is small, with pulsations decreasing as the opening increases. The inner flow line of the draft tube is disturbed when both the blade angle and opening are small. Additionally, the secondary frequency of the draft tube inlet is double that of the vane passing frequency. The discriminant number of the flow inhomogeneity approaches 0 under optimal flow conditions. The number increases continuously with the decrease in efficiency, and the flow in the three piers of draft tube becomes more nonuniform. The research results provide a reference for enhancing performance and ensuring the operational stability of Kaplan turbines. Full article

The diagrid core-tube structure has been widely used in high-rise buildings in recent years, but there are few studies on the sustainable energy dissipation measures and seismic performance improvement of such structural systems. Because the coupling beam is the element connecting the inner tube and the outer tube in the diagrid structure, it is the first seismic defense line and an important energy-dissipation member in the seismic design of the overall structure. Therefore, this paper replaces the traditional reinforced concrete coupling beam of the inner tube of the shear wall with a replaceable energy-dissipation steel coupling beam, and the strength, stiffness, and stability of the replaceable steel coupling beam are designed to improve the sustainability of the structure. By changing the position of the replaceable coupling beam, the relative stiffness of the inner and outer tubes of the diagrid tube structure, and the plane form of the structure, the static elastoplastic analysis and seismic response energy analysis of different diagrid tube structures are carried out, and the influence of the replaceable coupling beam on the sustainable seismic performance of the diagrid tube structure is studied. The results show that the replaceable coupling beams have little effect on the ultimate bearing capacity of the structure, but the ductility and sustainability of the structure are significantly improved, and the whole building layout is the optimal layout scheme. The setting of replaceable coupling beams makes the diagrid tube structure show hysteretic energy-dissipation earlier under the action of large earthquakes, and the proportion of hysteretic energy-dissipation is greatly improved, which reduces the inter-story drift ratios and the damage degree of the diagrid columns under the action of large earthquakes. When the relative stiffness of the outer tube of the diagrid tube structure is small or the plane form of the structure is a regular quadrilateral, the application of replaceable coupling beams is more effective in improving the ductility and sustainability of the structure and reducing the damage to the diagrid column under large earthquakes. Full article

The pyrolysis furnace, a critical component in a pyrolysis unit, inevitably faces operational challenges during its use. This study investigates a case of pyrolysis furnace failure, particularly focusing on an occurrence at the 90° lug elbow and furnace tube weld. The failure, characterized by a comprehensive fracture of the furnace tube in the circumferential direction along the weld vicinity, transpired within a timeframe significantly shorter than one-third of the design life. To unravel the root cause, a series of experiments was conducted on a sample extracted from the failed tube. These experiments, comprising visual inspection, chemical composition analysis, metallographic examination, microstructure analysis, fracture scanning electron microscopy, and energy spectrum analysis, collectively aimed at a comprehensive understanding of the failure mechanisms. The results disclosed that the fracture between the lug elbow and the inlet pipe stemmed from the presence of porosity and inclusions in the butt weld. The initiation of cracks was traced to the pores and inclusions in the fusion line of the inner wall of the pyrolysis tube, extending to connect with the pores in the heat-affected zone on the side of the pyrolysis tube parent material. Subsequently, under the influence of high temperature and stress, the cracks propagated, crept, and expanded along the circumference of the pyrolysis tube parent material until the final fracture occurred. In light of these findings, practical recommendations are proposed to mitigate the risk of similar failures in the future. Full article

This study proposed a new magnetic abrasive finishing (MAF) method, in which a 6-axis robot with a magnetic machining tool was used to polish the inner surfaces of curved tubes. We have also developed a magnetic machining tool jig, which can be fixed at the front of the 6-axis robot, rotating freely and suitable for polishing the inner surfaces of curved tubes. In this study, we focused on investigating the machining parameters in the initial machining stage and precision finishing stage. Based on the characteristics of machining parameters, a multi-stage MAF process was conducted to obtain an inner surface with high quality and high efficiency. The experimental results showed that both the roughness Ra and Rz of inner surface in the initial machining stage significantly decreased with the increase in the mixed magnetic abrasives, to as low as less than 20 nm Ra in the precision finishing stage when the machining parameters were appropriately adjusted. In addition, the roughness Ra of inner surface could be further reduced to less than 10 nm Ra in the multi-stage MAF process. Finally, the magnetic flux density cloud map and the magnetic field line distribution map were analyzed in Ansys Maxwell. Full article

The connection method of lengthening the steel tube of hollow concrete-filled sandwich circular steel tubes and threaded connections is proposed. The length, depth and position are the basic parameters. Twelve hollow concrete sandwich circular steel pipes with threaded connections were designed and subjected to axial compression tests. The axial compressive loading–longitudinal compressive displacement curves, axial compressive loading strain of steel tube curves and failure mode of the specimens are analyzed, and the effects of different parameters on the axial compressive-bearing capacity and stiffness of the specimens are studied. The results showed that within the range of parameters studied, the axial compression load–longitudinal compression displacement curves of the specimens were the linear elastic stage and the elastic–plastic stage, which can be divided into a yield-strengthening stage and a decreasing stage. The bearing capacity and strength of the lined threaded connection specimen are not inferior to those of the ordinary specimen or the welded specimen. The bearing capacity and strength of the specimen increase with the increase of the thread length. The bearing capacity and strength of the specimens connected with inner liner screws at the ends are higher than those connected with inner liner bolts at the middle. Full article

The mechanism of blast damage to steel-clad concrete-filled steel tube (SCCFST) arched protective doors is studied using the dynamic response characteristics of such loads under the action of blast shock wave loads, and the ultimate blast load-bearing capacity formula is derived based on the “plastic hinge” damage mode of the doors using limit analysis, which explores the effect of the blast shock wave. The effect of the design parameters of each component of the protective door on the load-bearing capacity subjected to blast shock waves is discussed. Results show that the damage mechanism under a uniform radial load on the outer surface of the SCCFST arched protective door is characterized by the plastic hinge lines at the two arch feet, which results in a slip fracture and renders the protective door unstable. The load-bearing capacity of the SCCFST arched protective door depends on the coordinated functioning of the cross-sectional outer cladding steel plate and inner connecting partition, concrete-filled steel tube, and restraining concrete outside the steel tube. The load-bearing capacity of each of the three parts differs with the varying cross-sectional occupancies. Full article

Because the initial speed of the seeds leaving the seed disk is too high, they collide and bounce off the inner wall of the seed guide tube, resulting in poor sowing quality when corn is sown at high speeds above 12 km/h. This study clarifies the primary factors affecting the stability of seed receiving and the accuracy of the seed entering the seed cavity, establishes the dynamic model of seed clamping, transportation, and releasing, and investigates the belt-type high-speed corn seed guiding device with the seed receiving system as the research object. It also proposes an improved method of adding herringbone lines on the finger surface to address this issue. Using EDEM software, a virtual experiment of seed-receiving performance was conducted, and the change trend of stress on seeds with and without a herringbone pattern and different wheel center distance as well as the change trend of the speed of seeds with various feeder wheel speeds and finger length, were both examined. The outcomes of the simulation demonstrate that the herringbone-lined feeder wheel could increase the stress on seeds. The average value of the stress on the seeds is the highest at the wheels’ center distance of 37 mm. The stability and speed fluctuation of seeds introduced into the seed cavity were better when the feeder wheel speed was 560 r/min. The speed of fluctuation and stability of the seeds introduced into the seed cavity were better when the finger length was 12 mm. The high-speed camera test on the test bench was used to verify the seed guiding process in accordance with the simulation results, and the outcomes were largely consistent. The study’s findings can serve as a theoretical foundation for a belt-type high-speed corn seed guiding device optimization test. Full article

Plasma content and distribution are key parameters in the dynamics of the inner magnetosphere. The plasmasphere contributes, for the most part, to the plasma mass density, and its properties are very dependent on the history of the magnetosphere and geomagnetic activity. In this work, we investigated plasmasphere dynamics and plasmasphere–ionosphere coupling, focusing on the refilling process that followed the geomagnetic storm that occurred on 1 June 2013. The equatorial plasma mass density used to evaluate the refilling rates was remotely sensed by observation of the field line resonance (FLR) frequencies of the geomagnetic field, driven by ultra-low-frequency magnetic waves. The FLR frequencies were retrieved by performing an analysis of signals detected by several station pairs of the European quasi-Meridional Magnetometer Array. We estimated the rate at which the refilling process occurred, concentrating on both the diurnal and the day-to-day refilling rates. The estimated contraction rate during the main phase of the storm was higher than $\sim 3.5$ $R_E{d}^{-1}$, while the average expansion rate was $\sim 0.4$ $R_E{d}^{-1}$. We investigated the radial dependence of the refilling rates, using a novel approach based on fit plasma mass density profiles, and we related their variation to the plasmasphere boundary layer and the zero-energy Alfvén boundary. We found evidence supporting the idea that flux tubes mapping in the region between these two boundaries experience an enhanced refilling process. Full article

A tube-integrated flow sensor is proposed in this study by integrating a micro-electro mechanical systems (MEMS) flow-sensing element and electrical wiring structure on the same copper on polyimide (COP) substrate. The substrate was rolled into a circular tube with the flow-sensing element installed at the center of the tube. The signal lines were simultaneously formed and connected to the Cu layer of the substrate during the fabrication of the sensing structure, thus simplifying the electrical connection process. Finally, by rolling the fabricated sensor substrate, the flow sensor device itself was transformed into a circular tube structure, which defined the airflow region. By implementing several slits on the substrate, the sensing element was successfully placed at the center of the tube where the flow velocity is maximum. Compared to the conventional sensor structure in which the sensor was placed on the inner wall surface of the tube, the sensitivity of the sensor was doubled. Full article

The connection method of lengthening the steel tube of concrete filled circular steel tubes by inner lining tube and threaded connection is proposed. Taking the length, depth, and position of the thread as the basic parameters, 12 concrete filled circular steel tubes connected by thread through inner lining tube were designed and manufactured, and an axial compressive test was carried out. The axial compressive loading-longitudinal compressive displacement curves, axial compressive loading-strain of steel tube curves, and failure mode of the specimens were analyzed, and the effects of different parameters on the axial compressive bearing capacity and stiffness of the specimens were studied. The results show that the axial compressive loading-longitudinal compressive displacement curves of the specimen can be divided into the elastic stage, elasto-plastic stage, and plastic reinforcement stage in the range of parameters studied in this paper. The bearing capacity and stiffness of the specimens connected by thread through inner lining tube are no worse than those of the unconnected specimen or the specimen connected by weld. Bearing capacity and stiffness of the specimen increase with the increase of thread length. The calculation method of the axial compressive bearing capacity of concrete filled circular steel tubes connected by thread through inner lining tube are suggested. Full article