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]

Many industrial and manufacturing processes exhibit complex and coupled fluid flow phenomena [...]

In this study, a specimen geometry for testing finger joints was developed using finite element simulation and proofed by experimental testing. Six different wood species and three adhesives were used for finger-jointing specimens. With the test specimen geometry, the bonding strength of the finger joints was determined without the usual self-locking of the joint. Under load, the test specimen geometry introduces maximum stress at the beginning of the bond line (adhesive zone). However, the test specimen geometry does not generate a symmetric stress state. The main difficulty here is the flank angle of the finger joint geometry. The wood species and adhesives significantly influenced the performance of the finger joints.

We modified the Zwart−Gerber−Belamri (ZGB) cavitation and RNG turbulence models based on their rotational motion characteristics, as well as simulating the phenomenon of small fluctuations in rotational speed due to the action of hydraulic excitation force, to increase the precision of numerical simulations of the cavitation characteristics of centrifugal pumps. According to the theory behind the enhanced model, the pressure gradient in the impeller runner changes uniformly, and the cavitation bubble initially manifests itself at the front edge of the blade’s suction. With the reduction in the effective margin, changes in the impeller flow channel’s pressure gradient increased, the blade’s suction-side cavitation area expanded, and the flow field’s internal disturbance enhanced, resulting in hydraulic loss to the centrifugal pump, considerably reduced operating performance, and the blade pressure side by the cavitation-affected area becoming smaller. The blade’s suction-surface pressur... [more]

This article presents an ultramodern modelling algorithm for predicting the remnant cellulose life cycle for oil-submerged power transformers based on the adaptive neuro-fuzzy interference system (ANFIS). The polymer characteristics, degree of polymerization (DP), and 2-furaldehyde (2FAL) of 100 power transformers were measured and collated, which were apportioned into 70 training databanks and 30 as testing datasets. The remnant cellulose life cycle of the transformer was predicted using the proposed ANFIS model characterized by polymer characteristics, DP and 2FAL as inputs. The proposed approach returns 98.23% training and 99.86% testing reliability. The proposed model was applied to 10 transformer case studies in predicting their remnant cellulose life cycle. To corroborate the proposed ANFIS, a comparative study was carried out by employing existing approaches in predicting the remnant life cycle of the case studies, and significant error margins were observed. At large, the resul... [more]

This article presents the preliminary results on the drying process in a fountain dryer designed and adapted to drying waist sawdust and/or chips of various morphology and moisture content. In terms of drying technology, it is important to reduce the demand for heat and electricity. The phenomena occurring during the drying of sawdust in a fountain dryer were analyzed. Modifications of a typical fountain dryer were proposed in order to dry the chips, to obtain appropriate moisture and quality suitable for the process of their further granulation for the production of pellets. The test stand and the most important properties of the fountain dryer were described and discussed. Such characteristic aims of the device, i.e., efficiency, combustion, air and exhaust gas flow measurements, among others, were presented. The characteristics of the sawdust drying curves as a function of temperature were also determined. Computer simulations of heat exchange, air, and exhaust gas flow velocities w... [more]

The slide valve-type direct-acting relief valve with external orifice (SVTDARVWEO) is widely used in hydraulic systems, and its response characteristics are influenced by key factors. It is of great significance to carry out research on the influencing factors of the response characteristics of the SVTDARVWEO. The working principle of the SVTDARVWEO is analyzed in the present study. The simulation model of the SVTDARVWEO is established using AMESim. The influence of the orifice diameter, viscosity coefficient, valve element mass, spring stiffness, oil seal length, and valve element diameter on the response characteristics of the SVTDARVWEO is studied. The results show that: (1) The smaller the orifice diameter is, the smaller the oscillation frequency, amplitude and maximum overshoot of pressure, flowrate, displacement and velocity are. (2) When the viscosity coefficient is 50 N/(m/s), 55 N/(m/s) and 60 N/(m/s), the pressure, flowrate, displacement and velocity oscillate periodically,... [more]

Accurate prediction of the compressive strength of concrete is of great significance to construction quality and progress. In order to understand the current research status in the concrete compressive strength prediction field, a bibliometric analysis of the relevant literature published in this field in the last decade was conducted first. The 3135 journal articles published from 2012 to 2021 in the Web of Science core database were used as the database, and the knowledge map was drawn with the help of the visualisation software CiteSpace 6.1R2 to analyse the field at the macro level in terms of spatial and temporal distribution, hotspot distribution and evolutionary trends, respectively. Afterwards, we go into the detail and divide concrete compressive strength prediction methods into two categories: traditional and machine-learning methods, and introduce the typical methods of each. In addition, a boosting-based ensemble machine-learning algorithm, namely the gradient boosting regr... [more]

This work presents an overview of (passive) solar chimney research, from the natural convection fundamentals to the recent progress for achieving thermohydraulic best-performance. Solar chimneys are attractive because they contribute to increasing the efficiency in air conditioning processes for dwellings and buildings, and therefore also aid to reduction in greenhouse gas emissions. A wide number of works dealing with solar chimneys (and Trombe walls or similar) shape designs, as well as with the inclusion of obstacles for disturbing the airflow, is commented in detail. Several numerical simulation procedures used in the literature are specially discussed, and different recommendations are pointed out to be considered for the appropriate numerical simulation of the operating modes of a solar chimney. Investigations aiming for the best performance conditions (for both thermal, and dynamic or ventilation modes) deserve special attention.

Wet fluidized bed granulation and coating processes have been widely used in the pharmaceutical and food industries. The complex gas−solid flow coupled with heat and mass transfer in such processes made it hard to form complete control over the apparatuses. To serve better design, scaling-up, and optimization of granulators and coaters, the underlying micro-scale mechanisms must be clarified. Computational fluid dynamics coupled with the discrete element method (CFD-DEM) provides a useful tool to study in-depth the gas-solid hydrodynamics of the granulation and coating processes. This review firstly introduced the fundamental theory of CFD-DEM from governing equations, force calculation, and coupling schemes. Then the application of CFD-DEM in simulating wet fluidized bed granulation and coating was presented. Specifically, the research focus and the role of CFD-DEM in resolving issues were discussed. Finally, the outlook on the development of CFD-DEM in the context of granulation and... [more]

MoS2 nanomaterials and ionic liquids (ILs) have attracted tremendous interest as the prime electrodes and electrolytes of supercapacitors. However, the corresponding charge storage mechanisms have not yet been clearly understood. Herein, we study the molecular-level energy storage mechanisms of the MoS2 electrode in imidazolium ionic liquid ([BMI+][PF6−]) using molecular dynamics (MD) simulation. The electric double-layer (EDL) structures of MoS2 electrodes in [BMI+][PF6−] electrolytes are comprehensively studied in terms of number density, MD snapshots, separation coefficient, and ion-electrode interaction energy. Based on this, the electric potential and electric field distributions are calculated by integrating Poisson equations. Importantly, a bell-shaped differential capacitance profile is proposed, different from the U-shaped curve from the conventional Gouy−Chapman theory. Especially, it can be well reproduced by the differential charge density curve in the Helmholtz layer. This... [more]