In order to obtain the damage characteristics of a roadway wall caused by a gas explosion, the damage evaluation theory of a roadway wall under the dynamic and static loads of a gas explosion is analyzed in this paper. Meanwhile, an evaluation method (overpressure−impulse criterion) is selected to evaluate the damage of the roadway wall under the impact load of the gas explosion. A mathematical model and a physical analysis model of the roadway wall damage are established by LS-DYNA software. The dynamic response of the roadway wall caused by the dynamic and static loads of the gas explosion is numerically simulated. The overpressure and impulse of gas explosion propagation are measured, while the damage data of the roadway wall under different overpressure and impulse loads are obtained. The P-I curves of the roadway wall under different dynamic and static loads of gas explosion are drawn. The fitting formula of P-I curves of the roadway wall is obtained. The influence of different ge... [more]

This paper proposes a timetable coordination method for transfer problems in a bus transit system. With a given bus network, a stochastic mixed-integer linear programming (MILP) model has been formulated to obtain coordinated bus timetables with the objective of minimizing a weighted sum of the average value of total waiting time and its average absolute deviation value, allowing for random bus travel time. The vital decision variable is the terminal departure offset time of each target bus trip within a certain off-peak period. The robust MILP model can also be used to solve the first-bus transfer problem with the introduction of several new linear constraints. A solution method based on the Monte Carlo simulation has been developed to solve the MILP model. Numerical experiments have been conducted for different scenarios. The results indicate that bus timetables coordinated by the developed model are capable of substantially reducing waiting time for transfer and non-transfer passeng... [more]

This work established a finite element analysis (FEA) model of an inserted tooth-type slip assembly under bear setting load and axial load, calculated the differences between the inserted teeth of the sidetracking packer slip-formed furrow shapes on the casing face, and analyzed the setting reliability of the inserted tooth slip sidetracking packer. The orthogonal optimization analysis of the structural parameters of the sidetracking packer was carried out on the basis of the furrow effect. Finally, the setting experiment was conducted with the inserted tooth slip sidetracking packer developed to verify correctness of the FEA model and the simulation results. The results show that in the FEA and calculation of the setting process of the inserted tooth-type slip, it is not only necessary to consider the furrow friction coefficient, but also the effect of the ridge on the furrow friction coefficient. The corresponding furrow friction coefficient varies according to the different furrow e... [more]

This paper proposed a semi-theoretical model to quantitatively predict leakage rate of tubing and casing premium connections. The geometric parameters of the sealing surface profile approximated by a sinusoidal micro-convex surface were first obtained based on the random normal distribution sampling method. With the actual area prediction formula for elastic−plastic contact of an axisymmetric sinusoidal micro-convex body based on the equivalent simulation principle, the circumferential leakage width and radial average leakage height of the micro-leakage channel between sealing surfaces were then acquired with the surface roughness and geometric mean contact pressure. At last, the actual micro-leakage rate of the premium connection was derived by considering the non-uniform contact pressure distribution between sealing surfaces. An example was investigated to validate the model and reveal the sealing and leakage characteristics, and anti-leakage measures were proposed. The results show... [more]

Fluid bed granulation is faced with a high level of complexity due to the simultaneous occurrence of agglomeration, breakage, and drying. These complexities should be thoroughly investigated through particle−particle, particle−droplet, and particle−fluid interactions to understand the process better. The present contribution focuses on the importance of drying and the associated challenges when modeling a granulation process. To do so, initially, we will present a summary of the numerical approaches, from micro-scale to macro-scale, used for the simulation of drying and agglomeration in fluid bed granulators. Depending on the modeled scale, each approach features several advantages and challenges. We classified the imposed challenges based on their contributions to the drying rate. Then, we critically scrutinized how these challenges have been addressed in the literature. Our review identifies some of the main challenges related to (i) the interaction of droplets with particles; (ii) t... [more]

The transmission in automobiles is the core component to ensure operational stability. Heat accumulation in the meshing process will reduce the transmission efficiency and affect the service life. Here, the essential physical process to improve transmission heat dissipation is the dynamic evolution process and the thermal transfer characteristics of lubricating oil fields during gear meshing. This paper presents a modeling and solving method for gear meshing lubrication and thermal transfer features based on the volume of the fluid model and piecewise linear interface construction (VOF-PLIC). The dynamic mesh technique combines spring smoothing and reconstruction to optimize the numerical solution process. The dynamic evolution law of gear meshing lubrication and thermal transfer is obtained by analyzing the lubrication evolution process under different speed/steering conditions. The results show that the proposed modeling and solving method could well reveal the lubrication and therma... [more]

In the process of metal cutting, a large amount of chips that are difficult to reuse will be produced, resulting in resource waste. As a novel metal forming process, cryogenic-temperature extrusion machining (CT-EM) can directly process chips into usable fins with a surface micro-groove structure, which has the advantage of high efficiency, energy saving and flexibility. In this study, the effects of four parameters (compression ratio λ, rake angle of the tool α, friction coefficient μ and the constraining tool corner radius R) on the effective stress, temperature and formability of micro-groove fins produced by CT-EM and room-temperature extrusion machining (RT-EM) are investigated. The results show that the maximum effective stress and formability of CT-EM are larger than that of RT-EM, which indicates that CT-EM has greater advantages in the preparation of micro-groove fins. At a λ of 0.7, the formability of CT-EM is the best. Reducing the λ and α, or increasing the μ, can improve t... [more]

Conventionally, fused deposition modeling (FDM) 3D printing allows for multiple color printing, but it is limited to only various monochromatic colors. Consequently, the effect of progressive color transition cannot be reflected. To produce the progressive 3-D color printing effect, the only solution is to implement stereolithography technology, which is particularly expensive. Therefore, the aim of this paper is to develop a color mixing mechanism to be incorporated into an FDM 3D printer, which is relatively inexpensive. The underlying idea is to pre-mix the color so that the FDM 3D printer can produce a progressive color printing effect. Three conceptual color mixing mechanisms are designed, i.e., a triangular stirring shaft, a rectangular spoiler stirring shaft, and a spiral blade stirring shaft. The mixing process is modeled based on the non-Newtonian fluid theory, in which the Carreau model is used to simulate the motion of pseudoplastic fluids in FDM 3D printing under forced mix... [more]

Liquid−liquid extraction has proven to be an aid in biologics manufacturing for cell and component separation. Because distribution coefficients and separation factors can be appropriately adjusted via phase screening, especially in aqueous two-phase systems, one stage is frequently feasible. For biologics separation, aqueous two-phase systems have proven to be feasible and efficient. The simple mixer−settler equipment type is still not standard in biologics manufacturing operations. Therefore, a scalable digital twin would be of aid for operator training, process design under the regulatory demanded quality by design approach for risk analysis, design and control space definition, and predictive maintenance. Autonomous operation is achieved with the aid of process analytical technology to update the digital twin to real time events and to allow process control near any optimal operation point. Autonomous operation is first demonstrated with an experimental feasibility study based on a... [more]

Automated crack detection technologies based on deep learning have been extensively used as one of the indicators of performance degradation of concrete structures. However, there are numerous drawbacks of existing methods in crack segmentation due to the fine and microscopic properties of cracks. Aiming to address this issue, a crack segmentation method is proposed. First, a pyramidal residual network based on encoder−decoder using Omni-Dimensional Dynamic Convolution is suggested to explore the network suitable for the task of crack segmentation. Additionally, the proposed method uses the mean intersection over union as the network evaluation index to lessen the impact of background features on the network performance in the evaluation and adopts a multi-loss calculation of positive and negative sample imbalance to weigh the negative impact of sample imbalance. As a final step in performance evaluation, a dataset for concrete cracks is developed. By using our dataset, the proposed me... [more]

As a new non-contact heating technology, induction heating technology has very broad application prospects in the field of fluid food heating. However, its application is inevitably affected by the heat concentration caused by uneven energy distribution. The uneven temperature distribution of the heating process will lead to the decrease in the quality of heating products. Therefore, based on the previous research, in order to improve the uniformity of heat distribution in the heating process, this study selected the susceptor with the greatest potential for efficient and the most uniform heating fluid to carry out the coupling simulation of electromagnetic heat transfer. The susceptor was simulated and optimized in three aspects: different power comparisons, the influence of structural change on temperature distribution uniformity, and the influence of physical property change of metal material on temperature distribution uniformity. The results show that the simulation results are in... [more]

The life of the hearth is the main limiting link of the campaign of a blast furnace. As the equipment for holding molten iron in the furnace, the high-temperature molten iron is in direct contact with the refractory, which makes the refractory have a larger temperature increase. If the temperature gradient inside the refractory is large, it generates large thermal stress and causes the refractory to crack. Blast furnace gas and molten iron intrude into the gap, which directly causes melting erosion and other chemical erosion with carbon bricks. It aggravates the erosion degree of the furnace and seriously affects the production life of the furnace. Therefore, the furnace often occurs with different types of severe depression erosion in the late service of the blast furnace. In this study, the calculation model of the thermal fluid-solid coupling considering the molten iron flow and the solidification of molten iron was established. This calculation model was applied to study thermal st... [more]

The complete characteristics of centrifugal pumps are crucial for the modeling of hydraulic transient phenomena occurring in pipe systems. However, due to the effort required to obtain these curves, pump manufacturers typically only provide basic information, particularly when the pump operates under normal conditions. To acquire the full characteristic curves based on the manufacturer’s normal performance curve, a machine learning (ML) model is proposed to predict full, complete Suter curves using a pump’s specific speed with the known parts of the Suter curve. The training data for the model are sourced from the available Suter curves from laboratory experiments. Subsequently, the proposed ML model combines several types of regression models in an attempt to find the most accurate prediction in terms of the root mean square error (RMSE). The result proved highly efficient, as the experiments attained a maximum RMSE value of 0.032 across the three categories of centrifugal pumps based... [more]

Brittle damage is a key factor restricting tool life extension. The peridynamic (PD) theory was applied to explain and predict the brittle damage of the near-field of the cutting edge of a cemented carbide microgroove turning tool (CCMTT) for the first time in this study, and the PD modeling of the complex surface was realized. The results showed that the PD modeling accuracy of the CCMTT can reach ±3.4%. The displacement of material points in the near-field of the cutting edge of the CCMTT is caused by the combined effect of the external load and the internal interaction force, and the former is dominant. There is no linear relationship between the displacement and the calculation time; instead, there are fluctuations and a maximum increase in the material point displacement in the main cutting direction. Only microdisplacements of material points in the near-field of the cutting edge occur under the given cutting conditions. The accumulation of microcracks caused by microdisplacement... [more]

This paper deals with the analysis of leakage characteristics of the proportional directional valve. These characteristics distinguish a real directional valve from an ideal one. The ideal directional valve is characterized by zero leakage due to its perfect geometry. The investigated element is the three-position four-way proportional directional valve with zero spool lap and feedback from the spool position. The spool position is measured by the inductive position sensor and processed by external electronics. Internal leakage occurs due to axial and radial clearances between the spool and the sleeve. The magnitude of axial clearances that occur at throttle edges and their effect on the directional valve leakage is the subject of research. The blocked-line pressure sensitivity curve, the leakage flow curve and the center flow curve are determined by experiment. Individual characteristics are determined for different working fluid temperatures and different supply pressures. The flow t... [more]

anion channelrhodopsin 1 (GtACR1) is a widely used inhibitor of optogenetics with unique conductance mechanisms and photochemistry. However, the molecular mechanism of light-gated anion conduction is poorly understood without a crystal structure for the intermediate state. In this study, we built the dark-state model based on the crystal structure of retinal and isomerized the model by twisting the C12-C13=C14-C15 dihedral step by step using molecular dynamics simulation. The conformational changes revealed the all-trans to 13-cis photoisomerization of the retinal chromophore cannot open the channel. There is no water influx, and a pre-opened K-like intermediate after photoisomerization of retinal is formed. During the opening of the ion channel, proton transfer occurs between E68 and D234. Steered molecular dynamics (SMD) and umbrella sampling indicated that the E68 and D234 were the key residues for chloride-ion conducting. We propose a revised channel opening pathway model of GtACR1... [more]

The study of mass transfer is essential in the food digestion process, especially when gastric acid interacts with food and nutrients dissolve in the gastric system. In this study, a computational fluid dynamics (CFD) model was built based on an in vitro study, which investigated the mass transfer in a tablet dissolution process in a beaker and stirrer system. The predicted mass transfer coefficients from the simulation aligned well with the experimental values. The effect of the type and rotation speed of the stirrers was also investigated. Mass transfer from the tablet was found to be closely related to the tablet Reynolds number of the fluid (ranging from 0 to 938) and the shear stress (0 to 0.167 Pa) acting on the tablet. The relationship between the power number (0.0061 to 0.196) and the Reynolds number for the impeller (719 to 5715) was also derived for different stirrers.

We demonstrated soldering of an electrical component (the metal-oxide semiconductor field effect transistor (MOSFET)) on a printed circuit bord (PCB) via solder paste heated by microwave irradiation. The behavior of the object soldered with solder heated in a microwave magnetic field and electric field were evaluated by using various microwave resonators. In the magnetic field, the solder paste was selectively heated by microwave irradiation. We confirmed that the MOSFET was connected onto the PCB without any damage and that the MOSFET operated normally. However, in an electric field, the solder paste cannot be heated by microwave irradiation because the edges of the PCB were selectively heated. Consequently, the MOSFET could not be connected onto the PCB. The strengths of the electromagnetic fields produced by different microwave resonators were numerically simulated to determine the optimal positions for microwave soldering. Based on the simulation results, microwave heating with sep... [more]

The classification of GM and non-GM maize kernels is fundamental for further analysis of the gene action in maize. Therefore, a complete and novel detection scheme based on near-infrared spectra was designed to distinguish GM and non-GM maize kernels. Hyperspectral images (935−1720 nm) of 777 maize kernels from 3 kinds were captured, and the average spectra of the maize kernels were extracted for modeling analysis. The classical modeling methods based on feature engineering were first studied, and the backpropagation neural network−genetic algorithm model showed the best performance with a prediction accuracy of 0.861. Then, novel modeling methods based on deep learning were developed. To dig out the interactive information between different bands and match the application scenarios, the original spectra were transformed into two-dimensional matrices before establishing the deep learning models. A modified convolution neural network (i.e., VGG net) with dilated convolution was finally... [more]

In this study, a three-dimensional CFD transient model is established for predicting species concentration distribution in the biodegradation of phenol in an airlift reactor (ALR). The gas−liquid flow in the ALR is determined by the Euler−Euler method coupled with the standard k-ε model, and the bubble size is predicted by the population balance model (PBM). A turbulent mass diffusivity model is developed to simulate the turbulent mass transfer process and to predict the species concentration distribution. No empirical methods are needed as the turbulent mass diffusivity can be expressed by the concentration variance c2¯ and its dissipation rate εc. A good agreement is found between simulated and experimental results in the literature. It is not reasonable to assume a constant turbulent Schmidt number because the calculated distribution of turbulent mass diffusivity is not identical to that of turbulent viscosity. Finally, the hydrodynamic characteristics and biodegradation performance... [more]

As an important component of hydrogen fuel cell vehicles, the air compressor with an air foil bearing rotates at tens of thousands of revolutions per minute. The heat generation concentration problem caused by the high-speed motor loss seriously affects the safe and normal operation of the motor, so it is very important to clarify the loss distribution of the high-speed motor and adopt a targeted loss reduction design for air compressor heat dissipation. In this paper, for an air compressor with a foil bearing with a rated speed of 80,000 rpm, an empirical formula and a three-dimensional transient magnetic field finite element model are used to model and calculate the air friction loss, stator core loss, winding loss and permanent magnet eddy current loss. The accuracy of the analytical calculation method is verified by torque test experiments under different revolutions, and the average simulation accuracy can reach 91.1%. Then, the distribution of the air friction loss, stator core l... [more]

As a fuel for power generation, high-pressure hydrogen gas is widely used for transportation, and its efficient storage promotes the development of fuel cell vehicles (FCVs). However, as the filling process takes such a short time, the maximum temperature in the storage tank usually undergoes a rapid increase, which has become a thorny problem and poses great technical challenges to the steady operation of hydrogen FCVs. For security reasons, SAE J2601/ISO 15869 regulates a maximum temperature limit of 85 °C in the specifications for refillable hydrogen tanks. In this paper, a two-dimensional axisymmetric and a three-dimensional numerical model for fast charging of Type III, 35 MPa, and 70 MPa hydrogen vehicle cylinders are proposed in order to effectively evaluate the temperature rise within vehicle tanks. A modified standard k-ε turbulence model is utilized to simulate hydrogen gas charging. The equation of state for hydrogen gas is adopted with the thermodynamic properties taken fro... [more]

This paper aims to quantitatively analyze the influence of natural groundwater flowing into the flow field of in situ leaching mining. The computational method was built to evaluate the effect of natural groundwater on the production efficiency of pumping wells for the in situ leaching of uranium, and the “flow ratio of groundwater” and related formulas were defined. C1 and C2 mining areas of an in situ leaching uranium mine in Inner Mongolia were taken as an example, and the effect on the “flow ratio of groundwater” when changing the flow quantity of injection wells and the position and length of the filter in the pumping and injection wells were compared. The results show that the variation in the “flow ratio of groundwater” of a whole mining area or a single pumping well in different production stages can be obtained by the neutral solution concentration value from the mining area’s numerical simulation. Regulating the position, length of the filter, and mode of fluid injection in a... [more]

Innovations in food drying processes are usually aimed at reducing drying time and improving the overall properties of dried products. These are important issues from an economic and environmental point of view and can contribute to the sustainability of the whole process. In this study, the effects of ultrasonic treatment on the drying kinetics of pumpkin pulp are investigated, and mathematical models to predict the drying kinetics are analyzed and optimized. The results show that ultrasonic pretreatment significantly reduces drying time from 451 to 268 min, with optimal processing parameters at 90% of the maximum ultrasonic power and a processing time of 45 min. The total color change of the samples was the lowest at the obtained optimal processing parameters. Based on the values (RMSE and R2) of the investigated mathematical drying models, it was found that the Weibull model is the best fit for the experimental data and is considered suitable for the drying kinetics of ultrasonicall... [more]

In the oil and gas drilling industry, cemented carbide teeth are one of the most widely used rock-breaking elements. In order to reveal the rock damage mechanism of tooth indentation, a series of tooth indentation experiments were conducted in this study, and an indentation simulation was also conducted as a supplement to the experiment. In the experiment, a new method to observe the inner damage status of the rock was put forward, i.e., utilizing the splitting action of the teeth to avoid unexpected rock damage that may affect the actual experiment results. The load-displacement curves and the damage status of the rock revealed that the wedge tooth was more efficient in fracturing and damaging the rock because the load requirement of the wedge tooth was lower, the narrow tooth crown generated larger specific stress in the rock; that rock-breaking advantage of the wedge tooth resulted from the occurrence of the compacted core and the tension stress generated by the core. According to t... [more]