Search Results (15)

We have improved the efficiency of the protection of occupants of cars by effectively reducing the injury and mortality rate caused by accidents when using safety belts. To ensure the protection efficiency of the safety belt outlet cover, we tested and adjusted the following parameters: the filling time, flow-front temperature and switching pressure, injection position pressure, locking force, shear rate, shear force, air hole, melting mark, material flow freezing-layer factor, volume shrinkage rate during jacking out, coolant temperature and flow rate in the cooling stage, part temperature, mold temperature difference, deflection stage, warping deformation analysis, differential cooling, differential shrinkage, and directional effect. Full article

Weird horizontal shapes of branches, in large branching estuaries, often cause significant flood risks and environment-related problems. People usually resort to engineering methods to improve the horizontal shape of the weird branches and solve related issues. The responses of the riverbed evolution of a branching estuary to anthropogenic activity are complicated because of complex estuarine hydrodynamics and sediment transports, especially when the project locates specially (e.g., at estuary outlets). The North Branch of the Yangtze Estuary has a narrow upper reach which is almost orthogonal to the South Branch and has a trumpet-shaped lower reach with a wide outlet. The weird horizontal shape of the North Branch brings significant flood risks to cities along this branch, the shrinkage of its entrance, and other problems. In this study, a regulation of the North Branch, which is launched at Guyuan Sand (GYS) just outside the exit of the North Branch, is taken as an example. The GYS regulation aims to improve the weird horizontal shape of the North Branch by building new layouts of outlets, by which people decrease the flood risk of the surrounding cities. The GYS regulation is studied using a 2D numerical model. The riverbed evolution of the Yangtze Estuary in a typical hydrological year is simulated, while the water/sediment fluxes at cross-sections of branches in the estuary during a spring/neap tide are quantitatively calculated. It is found that the regulation changes the rotational flows near the shore, and further reshapes the estuarine circulations of mass inside the outlets, especially exchanges of water/sediment between different branches. The regulation directly changes the riverbed evolution at the outlet of the North Branch, and meanwhile has significant indirect influences on the riverbed evolution of the entrance of the North Branch. The varying riverbed evolution at the entrance of the North Branch and the varying water/sediment fluxes, under different designs of regulations, are related and analyzed. An essential improvement for the weird horizontal shape of the North Branch by an engineering method is shown to be possible, while the regulation mechanism of the engineering method and the response of estuarine riverbed evolution to the regulation are clarified. This study provides a new insight for improving estuarine branches with weird horizontal shapes, by reshaping the tidal processes and the accompanying sediment transports in a branching estuary. Full article

A competing-rates model is presented to account for operational changes in the metastable β-Zr phase of the Zr-2.5Nb alloy used to make CANDU reactor pressure tubes and is used to predict temperature gradients at the outlet rolled joints using the decomposition of the β-Zr phase as a proxy for temperature. High temperatures decompose the β phase by enhancing the formation of small particles of ω and α phases. Fast neutron flux causes the ω and α phases to shrink. This process is assumed to depend on the total volume of the particles, because they are comparable to, or smaller than, the size of the neutron displacement cascades. The barrier energy for thermal growth was determined to be 2.43 eV, when an Arrhenius A factor of 10¹³/s was assumed. The cross section for (ω+α)-phase shrinkage is 24.5 barns for Zr-2.5Nb irradiated in CANDU reactors. Assuming that the shrinkage is dominated by the migration of self-interstitial point defects, a defect production efficiency of 1.4% was found. Full article

Flashing flows of initially sub-cooled water in a converging–diverging nozzle is investigated numerically in the framework of the two-fluid model (TFM). The thermal non-equilibrium effect of phase change is considered by an interfacial heat transfer model, while the pressure jump across the interface is ignored. The bubble size distribution induced by nucleation, bubble growth/shrinkage, coalescence, and breakup is described based on the interfacial area transport equation (IATE) and constant bubble number density model (CBND), respectively. The results are compared with the experimental data. Satisfactory prediction of the axial pressure distribution along the nozzle as well as the flashing inception, is achieved by the TFM-IATE coupling method. It was also found that the vapor production in the diverging section was overpredicted, and the radial gas volume fraction distribution deviated from the experiment. The radial diameter profiles exhibit opposite patterns at the nozzle throat and near the outlet, and similar trends can be observed for the superheated degree. A poly-disperse method is suggested to be introduced to describe the evolution of interfacial area concentration. Full article

In the process of the double-layer gas-assisted extrusion of plastic micro-tubes, the external size and surface quality of the micro-tubes are greatly affected by the size of the assisting gas inlet slit inside the mold. Therefore, in this experiment, a two-phase flow model was established based on a compressible gas and a non-compressible melt. The Polyflow finite element solution software module was used to solve the velocity field, temperature field, pressure field, and section size of the melt under the condition of double-layer gas-assisted extrusion in a mold under different gas inlet slit widths. The results show that, with an increase in the width of the gas inlet slit, the melt outlet velocity increases, the surface temperature increases, wall thickness shrinkage increases, and interior diameter expansion increases. In the process of gas-assisted extrusion, the thickness of the air cushion is affected by adjusting the size of the gas inlet slit, and, hence, changes the shape and size of the plastic micro-tubes. Full article

Super Typhoon Rai damaged Siargao’s tourism industry. Despite the reconstruction projects, there was still evidence of limited resources, destructed infrastructures, and destroyed natural resources. Therefore, this study aimed to examine the significant factors influencing tourists’ intentions to revisit Siargao after Super Typhoon Rai using feature selection, logistic regression (LR), and an artificial neural network (ANN). It employed three feature-selection techniques, namely, the filter method’s permutation importance (PI), the wrapper method’s Recursive Feature Elimination (RFE), and the embedded method’s Least Absolute Shrinkage and Selection Operator (LASSO). Each feature-selection technique was integrated into LR and the ANN. LASSO-ANN, with a 97.8146% model accuracy, was found to be the best machine-learning algorithm. The LASSO model performed at its best with a 0.0007 LASSO alpha value, resulting in 35 subfeatures and 8 primary features. LASSO subsets underwent the ANN model procedure, and the optimal parameter combination was 70% training size, 30% testing size, 30 hidden-layer nodes, tanh hidden-layer activation, sigmoid output-layer activation, and Adam optimization. All eight features were found to be significant. Among them, hedonic motivation and awareness of Typhoon Rai’s impact were considered the top-tier post-typhoon tourism factors, as they maintained at least 97% prediction accuracy. The findings could be elaborated by combining feature-selection techniques, utilizing demographic characteristics, assessing Siargao’s tourism before the typhoon, and expanding the context and participant selection. Nevertheless, none of the existing studies explored the combination of feature selection, LR, and ANNs in a post-typhoon tourism context. These unique methods and significant findings represent the study’s novelty. Furthermore, practical contributions were provided through economic resolutions focusing on tourism activities and communication revamping by the government, media outlets, and transportation companies. Full article

The water yield produced at the outlet of a sub-basin is the combination of multiple interacting land uses. In the majority of previous research, while accounting for the effect of land use and land cover (LULC) on water yield, the hydrologic components of a watershed have been attributed to the dominant land use class within that sub-basin. We adopted an approach to investigate the interaction effect of LULC on water yield (WYLD) using the Johnson–Neyman (JN) method. The soil and water assessment tool (SWAT) model was employed in the Urmia Lake Basin (ULB) to estimate the WYLD following successful calibration and validation of the model by stream flow. It was found that in each sub-basin, the effect of the soil class on the WYLD was statistically significant only when the area of rangeland was less than 717 ha and when the area of agricultural lands was less than 633 ha. On the other hand, the trend of stream flow was assessed over 70 years at two stations in the Urmia Lake Basin (ULB) using the Bayesian Estimator of Abrupt change, Seasonal change, and Trend (BEAST). The year 1991 turned out to be the most likely change point in both stations. A significant decrease in Urmia Lake’s water level started in 1995, which indicated that part of this shrinkage was most likely caused by water inflow reduction over a 4-year time delay. Besides identifying the most probable seasonal and trend change points, this method has the additional capability to analyze the uncertainty of estimated points, which was lacking in earlier methods. Full article

There is a growing concern for finding alternative solutions to construction materials in order to minimise their environmental impact as well as enhancing their service life. This study investigated the durability of cementitious mortars prepared by replacing fine aggregate (sand) with recycled tyre shreds and crumbs, aiming at providing an alternative outlet to tyre waste disposal. Tyre shreds obtained at different particle sizes, from fibres of 0.5–5.0 mm to crumbs of 0.1–0.85 mm in diameter, were used as fine aggregate replacement at 20% by volume. The strength of the mortar samples, their thermal conductivity and their water absorption rate were tested at the age of 28 days and after 20 freeze/thaw cycles. The results showed that the mortar containing tyre crumbs at lower particle sizes resulted in negligible shrinkage, improved freeze/thaw resistance, a reduced water absorption by up to 52% and an improved thermal resistivity. Full article

Many patients with outlet obstruction secondary to prostatic enlargement have lower urinary tract symptoms (LUTSs) and an increased frequency of micturition. The standard treatment is transurethral resection of the prostate (TURP), which alleviates obstruction and symptoms. However, after TURP, 20–40 percent of patients continue to experience LUTSs. The aim of the present study in rats was to identify the mechanisms that do not normalize after the removal of the obstruction and that could explain the persisting symptoms. We had microarray data from control, obstructed, and de-obstructed female rat bladders, which made it possible to study 14,553 mRNA expressions. We also had a bank of electron micrographs from similar detrusors. Microarrays: There were significant differences between the control and obstructed bladders for 1111 mRNAs. The obstructed and de-obstructed bladders differed significantly for 1059 mRNAs. The controls and the de-obstructed bladders differed significantly for 798 mRNAs. We observed many mRNAs that were increased in the obstructed bladder and then decreased to control levels after de-obstruction, and many mRNAs that were decreased in the obstructed bladder and then increased following de-obstruction. mRNAs that were significantly higher or lower in the de-obstructed bladder than in the control bladder were also found. Ultrastructure: The detrusor cells in the obstructed bladders had cross-sectional areas that were much larger than those in the controls. The control cells had smooth outlines and similar cross-sectional areas. The de-obstructed detrusor cells had larger cross-sectional areas than the controls, as well as corrugated surfaces. The cell areas varied, suggesting that the shrinkage of the de-obstructed cells was not even. We did not find any points of contact of the gap junction plaque type between the detrusor cells. There were abundant finger-like processes between the detrusor cells in the obstructed and in de-obstructed bladders, which were only occasionally found in the control detrusors. They are the only possible localization for gap junction channels. The de-obstructed rat bladder is not an organ with properties intermediate between those of the control and obstructed bladders. Instead, de-obstructed bladders have gene expressions, morphologies, and functional properties of the individual cells and their organization, which make them distinctly different from both control and obstructed bladders. Full article

Improving the efficiency of transport of coal water slurries (CWSs) and determining pipe wear both necessitate accurate predictions of flow characteristics in pipelines with complex geometries. At the bends of the channels, the flow is significantly influenced by the bend curvature, flow rate, and the rheological properties of the slurries that are viscoplastic. Herein, we numerically simulated the flow of CWS in curved channels with different curvature ratios, at different flow rates, and using different rheological models, respectively. The results showed that, due to the yield stress on the cross-stream slices, the velocity profiles showed an unyielded plug. The plug deflects outwards in most circumstances, except at the bend core in the highly curved channel, and, at the same time, at the lower conveying rate, which is due to the fact that the larger inner-wall-pointed pressure gradient has to be balanced by large velocities at the inner bend and, hence, the centrifugal effects are weakened at the lower conveying rate. Interestingly, the larger curvature, together with a higher conveying rate, induces a kidney-shaped velocity field at the bend exit, with two separated up and down velocity maximum zones, due to the larger wall shear stresses at the top and bottom than occur in the other cases. The bend brings in a secondary flow consisting of the following: an inward transverse flow at the bend entrance; two Dean swirls in symmetry in the vertical direction at the slices of the bend core and bend exit; and decayed swirls near the outlet. As the curvature ratio increases, the location of the strongest swirls switches from the bend core to the bend exit, since the flow in the highly curved channel requires a longer distance to fully develop the vortices. Decrease in the yield stress and decrease in the consistency index induce a shrinkage of the plug and enhance the streamwise flow and, thus, decrease the cross-stream secondary flow, especially in the channel with the larger curvature. Full article

Miscible viscous fingering occurs when a less viscous fluid displaces a more viscous one in porous media or a Hele–Shaw cell. Such flow instabilities are of particular interest in a variety of applications in flows and displacements in subsurface energy and environment systems. In this study, we investigate the miscible viscous fingering dynamics experimentally using water to displace glycerol in a sealed Hele–Shaw cell with two wells located in it instead of at the boundary or corners. We comprehensively examine the spatial and temporal variations of fingering dynamics, different flow regimes, and how they are affected by the water injection rate and control of pressure or rate at the outlet. Alongside the widely recognized diffusion-dominated and convection-dominated flow regimes, we identify three new regimes: a slow expansion regime prior to breakthrough, a rapid shrinkage regime immediately after breakthrough, and a uniform, slow expansion regime without fingering instability. Each regime is characterized by interesting flow dynamics, which has not been reported previously. The duration of each regime depends on the water injection rate and whether constant pressure or a constant production rate is applied at the outlet. The variations of swept area, interfacial length, and count of fingers are also quantitatively examined. This study provides new insights into the fundamental mechanisms for miscible fluid displacements in a variety of applications such as CO₂ sequestration, hydrogen storage, enhanced oil recovery, and groundwater contaminate remediation. Full article

In response to the problems of small working width and low operating efficiency of existing hydraulic scouring lotus root harvesters, a wide-width hydraulic scouring system was designed based on a wide-width self-propelled lotus root harvester. The main parameters of the key components were determined through theoretical analysis of the water flow energy of the hydraulic scouring system pipelines. An experimental study was also carried out on the main factors affecting the working performance of this hydraulic scouring system. Through hydrodynamic simulation tests, the effect of nozzle type and constriction section structure on the turbulence intensity at the nozzle outlet and the pressure loss per unit mass of fluid between the nozzle inlet and outlet sections were compared and analysed. The test yielded conical-cylindrical nozzle geometry parameters for nozzle inlet diameter of 40 mm, shrinkage angle of 30°, nozzle outlet straight section length of 20 mm, nozzle outlet diameter of 16 mm, the nozzle had better flushing performance. Single-factor tests were carried out with nozzle outlet pressure, scouring angle and nozzle height from the mud surface as influencing factors. Based on the optimum effective scour depth, a three-factor, three-level Box–Behnken central combination design test was completed. The primary and secondary factors affecting the effective scouring depth were obtained in the following order: nozzle height from the mud surface, nozzle outlet pressure, and scouring angle. Finally, the performance test of the hydraulic scouring system was completed. Results showed that when the nozzle outlet pressure of 0.30 MPa, the scouring angle of 60° and the nozzle height from the mud surface of 0 mm, the effective scouring depth was 395 mm, the lotus root floating rate was 90% and the damage rate was 5%, which meet the requirements of lotus root harvesting operations. Full article

Municipal incinerator bottom ash (MIBA) and sewage sludge ash (SSA) are secondary wastes produced from municipal incinerators. Landfills, disposal at sea, and agricultural use have been the major outlets for these secondary wastes. As global emphasis on sustainability arises, many have called for an increasing reuse of waste materials as valuable resources. In this study, MIBA and SSA were mixed with clay for ceramic tile manufacturing in this study. Raw materials firstly went through TCLP (Toxicity Characteristic Leaching Procedure) to ensure their feasibility for reuse. From scanning electron microscopy (SEM), clay’s smooth surface was contrasted with the porous surface of MIBA and SSA, which led to a higher water requirement for the mixing. Specimens with five MIBA mix percentages of 0%, 5%, 10%, 15%, and 20% (wt) and three SSA mix percentages of 0%, 10%, and 20% (wt) were made to compare how the two waste materials affected the quality of the final product and to what extent. Shrinkage tests showed that MIBA and SSA contributed oppositely to tile shrinkage, as more MIBA reduced tile shrinkage, while more SSA encouraged tile shrinkage. However, as the kiln temperature reached 1150 °C, the SiO2-rich SSA adversely reduced the shrinkage due to the glass phase that formed to expand the tile instead. Both MIBA and SSA increased water tile absorption and reduced its bending strength and wear resistance. Increasing the kiln temperature could effectively improve the water absorption, bending strength, and wear resistance of high MIBA and SSA mixes, as SEM showed a more compact structure at higher temperatures. However, when the temperature reached 1100 °C, more pores appeared and seemingly exhausted the benefit brought by the higher temperature. Complex interactions between kiln temperature and MIBA/SSA mix percentage bring unpredictable performance of tile shrinkage, bending strength, and water absorption, which makes it very challenging to create a sample meeting all the specification requirements. We conclude that a mix with up to 20% of SSA and 5% of MIBA could result in quality tiles meeting the requirements for interior or exterior flooring applications when the kiln temperature is carefully controlled. Full article

Finding an appropriate shape for the releasing building is thoroughly relevant given the energy dissipation and safety requirements of a high dam in a sediment-laden river. Thirty-six physical experiments on trajectory energy dissipation were conducted, researching the influence of three overflow shapes (contraction ratios of 0.5, 0.4, and 0.3) with four sediment concentrations (0, 50, 150, and 250 kg/m³) on the discharge, flow regime, and hydrodynamic pressure of a plunge pool slab. The experimental results demonstrated that the flow coefficient gradually decreased as the contraction ratio decreased in a relatively high weir head, regardless of the sediment concentration. The water nappe narrowed and the length of the longitudinal trajectory increased as the outlet shrinkage and sediment concentration decreased. With the increase in sediment concentration, the nappe regime approached stability, and the flow in the plunge pool tended toward small rolling, causing the impact pressure and fluctuating pressure to increase. Changes in overflow shape had little effect on the position of pressure peak, but the value became lower as the ratio diminished. The influence on the hydrodynamic pressure by outlet shrinkage became attenuated while the sediment concentration increased. The fluctuating energy and vortex scale were enhanced due to the increased viscosity with increasing sediment concentrations. Full article

The liquefied natural gas (LNG) tank outlet pipe is the weak part of any LNG vaporizing station. Due to the ultralow temperature characteristics of LNG, pipeline damage or leakage may cause major accidents. This paper used the finite element analysis method and the CAESAR II software to analyze the stresses of LNG storage tank outlet pipes and flanges in a LNG vaporizing station, the influencing factors (compensator type, compensator position, LNG density, pressure, temperature) are analyzed, and stress reduction measures are discussed. According to the results of the analysis, the following main conclusions can be obtained: (1) the most dangerous working condition of the LNG storage tank outlet pipe is the precooling condition; under this condition, the comprehensive stress, displacement and support force are the largest; (2) compared with the Z-type and L-type compensators, the effect of the π-type compensator to reduce the stress of the low temperature pipe is the best; (3) when the length of the cold tightening unit is 40% of the cold shrinkage, the stress reduction effect is the best. Full article