The connection between an intake fan and a ventilation shaft must be designed in such a way that it minimizes the energy waste due to singularity losses. As a result, the questions of which radius of curvature to use and if guide vanes have to be included need to be answered. In that case, the variables such as the number, upstream and downstream penetration length, radius of curvature, and width of the vanes, need to be defined. Although this work is oriented to mine ventilation, these questions are usually valid in other engineering applications as well. The objective of this study is to define the previously mentioned variables to determine the optimal design combination for the radius/diameter relationship (r/D). Computational fluid dynamics was used to determine the shock loss factor of seven elbow curvature ratios for a 3 m diameter duct and fan, with and without guide vanes to estimate the best performing configuration and, therefore, to maximize the fan airflow volume. The meth... [more]

In response to the increasing energy demand in Taiwan and the global trend of renewable energy development, Kuroshio energy is a potential energy source. How to extract this invaluable natural resource has then become an intriguing and important question in engineering practices. This study reported the results of a feasibility study for a nozzle-diffuser duct (NDD) as the Kuroshio currents energy harvester. The computational fluid dynamics (CFD) software ANSYS Fluent was employed to calculate the drag and added mass coefficients of the duct anchored to the seabed. Those coefficients were further imported into Orcaflex to simulate the motion of the duct under normal and storm wave conditions. Results showed that the duct was stable 25 m below the sea surface under normal wave conditions. When the wave condition changed to storm waves, the duct needed to dive into at least 90 m below the sea surface to regain its stability and obtain high power take-off (PTO). An optimal design nozzle-d... [more]

Hydrogen fluoride (HF) is a typical dangerous gas in the fluorine chemical industry. Its leakage is one of the most common types of accidents in this industry, and it poses a serious threat to personnel safety and health, environmental sanitation, and social stability. In this paper, the process and consequences of an HF leakage accident in a fluorine chemical plant were simulated by using computational fluid dynamics (CFD) simulation software, and hazardous areas (lethal area, severe injury area, light injury area, and maximum allowable concentration area) of HF diffusion were determined according to the HF concentration corresponding to the degree of personal injury. Moreover, the effects of wind speed and height on hazardous areas were analyzed. The research results of this paper provide model support for similar enterprises to predict the consequences of harmful gas leakage accidents, and give suggestions on emergency evacuation and rescue work, which have practical application sig... [more]

In order to broaden the application of vortex tubes (VOTU) in industry and to improve the efficiency of cooling and heating, numerical simulations of vortex tubes were carried out. In this study, the temperature, velocity, and pressure fields of three VOTUs with inlet nozzles of 2, 3, and 6 were investigated at different inlet pressures based on previous experimental data and by three-dimensional numerical simulation. It was found that the increase of inlet pressure leads to the increase of energy separation between the hot and cold ends of the three VOTUs. As the number of inlets increases, the pressure difference between the tube wall and the core region gradually strengthens. In contrast, the pressure in the tube center is not affected by the inlet pressure. The number of nozzles affects the inlet and outlet temperatures of the VOTU. When the number of nozzles is 3, and the inlet pressure is 0.6 MPa, the VOTU shows the maximum hot and cold outlet temperature difference of 66 K. The... [more]

This paper focuses on the model of gas hydrate formation in an experimental device, which allows the circulation of the resulting mixture (water and gas) and significantly accelerates the process of hydrate formation in the laboratory. A 3D model was developed to better imagine the placement of individual parts of the device. The kinetics of hydrate formation were predicted from equilibrium values of chemical potentials. The aim of solving the equations of state gases in the mathematical model was to optimize the parameters involved in the formation of hydrates. The prediction of the mathematical model was verified by numerical simulation. The mathematical model and numerical simulation predict the chemical reaction evolving over time and determine the amount of crystallized water in the reactor. A remarkable finding is that the deviation of the model and simulation at the initiation the calculation of crystallized water starts at 76% and decreases over time to 2%. Subsequently, the nu... [more]

The products generated by the electrochemical reaction in the PEM fuel cell (PEMFC) are mainly concentrated in the flow field on the cathode side of the bipolar plate, and the oxygen introduced on the cathode has higher requirements to improve its diffusion performance by using the flow field structure. For this reason, the optimization of the cathode flow field of the PEMFC is essential. Inspired by the structure of a spider web, this paper proposes a novel spider-web-type flow field. In this kind of flow field, the shape of a polygonal structure and the number of layers of spiral flow channels are the two most crucial variables. In order to explore the impact of these two variables on the cathode flow field, complete three-dimensional PEMFC models with different values of the two variables were established, and the models were simulated by the method of CFD. By observing the results of oxygen distribution, the water removal performance and fuel cell output performance of different sc... [more]

In this paper, a numerical investigation was carried out on the performances of a designed axial flow pump for a large cavitation tunnel. From this, the flow characteristics, force, and torque performance of the axial flow pump were investigated, and the rotating speeds of the impeller satisfying the test section speed performances required in the large cavitation tunnel were estimated. The axial flow pump was modeled such that the impeller, stator, and nacelle were located in a cylindrical tunnel. The calculations were carried out for incompressible steady-state turbulent flow considering the impeller rotating. The performance of the pump was confirmed, finding that the head gain was caused by the pressure jump downstream of the pump. The performance of the stator was confirmed to be good enough to refine the tangential flow due to the impeller rotating. To investigate the operating performance of the large cavitation tunnel, the head loss of the entire tunnel without the pump was obt... [more]

Carbon dioxide (CO2) is one of the major atmospheric greenhouse gases (GHG). The continuous increase of CO2 concentration and its long atmospheric lifetime may cause long-term negative effects on the climate. It is important to develop technologies to capture and minimize those emissions into the atmosphere. The objective of this work is to design and study theoretically and experimentally a numbering-up/scale-out membrane microreactor in order to be used as a capture system. The main aim of the work is to obtain an even flow distribution at each plate of the reactor. Nearly uniform flow distribution was achieved at each layer of the numbering-up microreactor according to the carried-out CFD models. The maximum difference between the average velocities was less than 6% for both gas and liquid flows. To obtain better flow distribution into the microreactor, the radius of the inlet/outlet tube was optimized. Results from CFD and experimental simulations do not match, and slightly maldist... [more]

This study is concerned with droplet separation using wave-plate mist separators. The influence of continuous phase velocity, droplet size, and geometry on droplet removal efficiency has been investigated. The following modifications were analysed: drainage channel presence, length, angle, and modification to the streamlined shape. Furthermore, the influence of the physical parameters of the separated substances on separator efficiency was investigated. Calculations were conducted using computational fluid dynamics (CFD). The results were compared with the experimental data from the literature. Based on the results obtained, a new shape of drainage channels was proposed, which is characterised by high droplet removal efficiency with relatively low pressure drop.

Adaptation of metabolism is a response of many eukaryotic cells to nutrient heterogeneity in the cell microenvironment. One of these adaptations is the shift from respiratory to fermentative metabolism, also called the Warburg/Crabtree effect. It is a response to a very high nutrient increase in the cell microenvironment, even in the presence of oxygen. Understanding whether this metabolic transition can result from basic regulation signals between components of the central carbon metabolism are the the core question of this work. We use an extension of the René Thomas modeling framework for representing the regulations between the main catabolic and anabolic pathways of eukaryotic cells, and formal methods for confronting models with known biological properties in different microenvironments. The formal model of the regulation of eukaryote metabolism defined and validated here reveals the conditions under which this metabolic phenotype switch occurs. It clearly proves that currently k... [more]

The fluidized catalytic cracking (FCC) unit is the primary production unit for gasoline and olefins in refineries. Improving product yield and processing capacity is closely related to the economic benefits of refineries. In this paper, we use the Aspen HYSYS software to model the mechanism of an 800 kt/a FCC unit in China. The simulation of the FCC unit based on the 21-lump models and the simulation results are in good agreement with the actual factory production data. Then we find out the optimization method to improve the product yield and processing capacity through the model research. The results of the study indicate the following optimization plans: when keeping the riser outlet temperature (ROT) in the range of 535~545 °C, it can increase the yield of gasoline and liquefied petroleum gas (LPG) by up to 5%; when keeping the riser outlet temperature (ROT) in the range of 510~520 °C, it can increase the yield of gasoline and diesel by up to 0.5%; the optimal ROT of control tempera... [more]

The double-suction centrifugal pumps installed along the Yellow River in China face serious sediment erosion due to the high sediment content which causes the poor operation efficiency of the pump units. The particle motion characteristics and erosion characteristics in a pump under different flow rates and different particle concentrations were numerically simulated based on the particle track model of solid-liquid two-phase flow. The results show that the flow rate has a significant effect on the particle tracks and the erosion caused by the particles in the impeller. The total erosion rate is positively correlated with the flow rate, and increases with the increase in flow rate. The vortex and secondary flow in the impeller have obvious influence on the particle trajectory, which increases the particle concentration at the trailing edge of the pressure surface and intensifies the impact erosion in this area. The particles carried by the vortex intensifies the local erosion. The part... [more]

Transfer chutes for bulk material conveying systems have significant importance in ship loading and unloading and are ‘worn’ from large mass flow and fast granular material flow conditions. In this investigation, the impact forces of different granular materials on the transfer chute wear process are considered; the DEM−FEM (Discrete Element Method−Finite Element Method) coupling method was used to calculate the wear and the deformation of the transfer chute. The stress−strain and cumulative contact energy from three different granular materials were analyzed under different working conditions. The results show that the wear, stress−strain, and cumulative contact energy of the transfer chute are closely related to the belt speed, the chute inclination angle, and the types of granular materials; the impact force and the stress−strain on the transfer chute achieves maximum value under a 4 m/s belt speed condition; meanwhile, with the increase of belt speed by 0.5 m/s, the wear of the tra... [more]

This paper deals with a mathematical modeling of flow stability of Newtonian and non-Newtonian fluids in the gap between two concentric cylinders, one of which rotates. A typical feature of the flow is the formation of a vortex flow, so-called Taylor vortices. Vortex structures are affected by the speed of the rotating cylinder and the physical properties of the fluids, i.e., viscosity and density. Analogy in terms of viscosity is assumed for non-Newtonian and magnetorheological fluids. Mathematical models of laminar, transient and turbulent flow with constant viscosity and viscosity as a function of the deformation gradient were formulated and numerically solved to analyze the stability of single-phase flow. To verify them, a physical experiment was performed for Newtonian fluids using visualizations of vortex structures—Taylor vortices. Based on the agreement of selected numerical and physical results, the experience was used for numerical simulations of non-Newtonian magnetorheologi... [more]

In systems biology, biological phenomena are often modeled by Ordinary Differential Equations (ODEs) and distributed in the de facto standard file format SBML. The primary analyses performed with such models are dynamic simulation, steady-state analysis, and parameter estimation. These methodologies are mathematically formalized, and libraries for such analyses have been published. Several tools exist to create, simulate, or visualize models encoded in SBML. However, setting up and establishing analysis environments is a crucial hurdle for non-modelers. Therefore, easy access to perform fundamental analyses of ODE models is a significant challenge. We developed SBMLWebApp, a web-based service to execute SBML-based simulation, steady-state analysis, and parameter estimation directly in the browser without the need for any setup or prior knowledge to address this issue. SBMLWebApp visualizes the result and numerical table of each analysis and provides a download of the results. SBMLWebAp... [more]

Background: The outbreak of the coronavirus (SARS-CoV-2) has drastically affected the human population and caused enormous economic deprivation. It belongs to the β-coronavirus family and causes various problems such as acute respiratory distress syndrome and has resulted in a global pandemic. Though various medications have been under trial for combating COVID-19, specific medicine for treating COVID-19 is unavailable. Thus, the current situation urgently requires effective treatment modalities. Nigella sativa, a natural herb with reported antiviral activity and various pharmacological properties, has been selected in the present study to identify a therapeutic possibility for treating COVID-19. Methods: The present work aimed to virtually screen the bioactive compounds of N. sativa based on the physicochemical properties and docking approach against two SARS-CoV-2 enzymes responsible for crucial functions: 3CLpro (Main protease) and NSP15 (Nonstructural protein 15 or exonuclease). Ho... [more]

Studying the characteristics of wind speed is essential in wind speed prediction. Based on long-term observed wind speed data, fractal dimension analysis of wind speed was first conducted at different scales, and persistence in wind speed was evaluated based on fractal dimensions in this paper. To propose a more accurate model for wind speed prediction, the wavelet decomposition method was applied to separate the high-frequency dynamics of wind speed data from the low-frequency dynamics. Chaotic behaviors were studied for each decomposed component using the largest Lyapunov exponents method. A proposed hybrid prediction method combining wavelet decomposition, a chaotic prediction method and a Kalman filter method was investigated for short-term wind speed prediction. Simulation results showed that the proposed method can significantly improve prediction accuracy.

Vanes and baffles are often used as flow distributors where uniform flow is required in the apparatus of large cross-section surface areas. As an alternative, perforated plates with a range of open area ratios are applied to produce required gas flow homogeneity. Usually, the plates with various open area ratios are combined into large panels, of which total surface area can reach hundreds of square meters for large-sized industrial apparatus. Numerical modelling of the flow through such panels can be thought of as overly complex, time-consuming, and inefficient due to numerous small open area ratios in the plates and large differences in dimensions between open area ratios and free-stream areas. For this reason, numerical models of gas flow are limited to single plates only with constant open area ratios. A new indirect modelling approach of gas flow through the perforated plates panel with structural elements and various open area ratios with application of the porous media model is... [more]

Tourism makes a significant contribution to the economy of almost every country, so accurate demand forecasting can help in better planning for the government and a range of stakeholders involved in the tourism industry and can aid economic sustainability. Machine learning models, and in particular, deep neural networks, can perform better than traditional forecasting models which depend mainly on past observations (e.g., past data) to forecast future tourist arrivals. However, search intensities indices (SII) indicators have recently been included as a forecasting model, which significantly enhances forecasting accuracy. In this study, we propose a bidirectional long short-term memory (BiLSTM) neural network to forecast the arrival of tourists along with SII indicators. The proposed BiLSTM network can remember information from left to right and right to left, which further adds more context for forecasting in memory as compared to a simple long short- term memory (LSTM) network that c... [more]

This study focused on heavy gas dispersion under the terrain conditions of street canyons. The effects of street aspect ratio and height ratio were investigated, and the influence of environmental wind speed in the typical ideal street canyon terrain was explored. The results indicated that the surrounding flow field distributions in street terrains were dominated by higher buildings. In addition, when the building height was held constant, the flow field was affected by the joint influence of the two isolated buildings. The interception effect of the street canyon on upstream pollutants declined with the decrease in the street canyon’s aspect ratio. In addition, when the height ratios were different, a large quantity of upstream pollutants accumulated on the windward side of higher buildings. The relative concentration per unit area inside the canyon was affected by the air circulation inside and outside the canyon and the size of the dispersion space. The increase in the environmenta... [more]

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) is a type of Ribonucleic Acid (RNA) coronavirus and it has infected and killed many people around the world. It is reported that the receptor binding domain of the spike protein (S_RBD) of the SARS-CoV-2 virus is responsible for attachment to human angiotensin converting enzyme II (ACE2). Many researchers are attempting to search potential inhibitors for fighting SARS-CoV-2 infection using theoretical or experimental methods. In terms of experimental and theoretical research, Cefuroxime, Erythromycin, Lincomycin and Ofloxacin are the potential inhibitors of SARS-CoV-2. However, the interactive mechanism of the protein SARS-CoV-2 and the inhibitors are still elusive. Here, we investigated the interactions between S_RBD and the inhibitors using molecular dynamics (MD) simulations. Interestingly, we found that there are two binding sites of S_RBD for the four small molecules. In addition, our analysis also illustrated that hydro... [more]

Enzymatic hydrolysis processes can be used to produce organic nutrient media from renewable raw materials. However, many of these processes are not optimally designed, so expensive enzymes and substrates are wasted. Mathematical models and Digital Twins (DTs) are powerful tools, which can be used to optimize bioprocesses and, thus, increase the yield of the desired products. Individual enzymatic hydrolysis processes have already been modeled, but models for the combined starch hydrolysis and proteolysis, or DTs, are not available yet. Therefore, an easily adaptable, dynamic, and mechanistic mathematical model representing the kinetics of the enzymatic hydrolysis process of the combined starch hydrolysis and proteolysis was developed and parameterized using experimental data. The model can simulate the starch hydrolysis process with an agreement of over 90% and the proteolysis process with an agreement of over 85%. Subsequently, this model was implemented into an existing DT of a 20 L s... [more]

Currently, a large amount of information is presented graphically. However, visually impaired individuals do not have access to visual information. Instead, they depend on tactile illustrations—raised lines, textures, and elevated graphics that are felt through touch—to perceive geometric and various other objects in textbooks. Tactile graphics are considered an important factor for students in the science, technology, engineering, and mathematics fields seeking a quality education because teaching materials in these fields are frequently conveyed with diagrams and geometric figures. In this paper, we conducted a systematic literature review to identify the current state of research in the field of automatic tactile graphics generation. Over 250 original research papers were screened and the most appropriate studies on automatic tactile graphic generation over the last six years were classified. The reviewed studies explained numerous current solutions in static and dynamic tactile gra... [more]

In this paper, a new DEM calibration procedure based on two different types of procedures to compare simulation with experiments is proposed. The aim is to find the values of the interfacial adhesive surface energy and the coefficient of rolling friction between the particles to be used in the simulation. The approach adopted is the so-called Bulk Calibration method. The experimental values of the angle of repose and unconfined yield strength, found with a static testing method and by shear testing, respectively, are compared, respectively, with the angle of repose, found in a simulation reproducing the experimental procedure, and the unconfined yield strength, obtained from an idealized uniaxial testing procedure. The simulated DEM particles are spheres equipped with the Hertz Mindlin with JKR contact model. The results suggest that a bulk calibration approach is not able to provide results that are consistent with two simple bulk property evaluations and, therefore, direct ways to es... [more]

The cancelation of bookings puts a considerable strain on management decisions in the case of the hospitability industry. Booking cancelations restrict precise predictions and are thus a critical tool for revenue management performance. However, in recent times, thanks to the availability of considerable computing power through machine learning (ML) approaches, it has become possible to create more accurate models to predict the cancelation of bookings compared to more traditional methods. Previous studies have used several ML approaches, such as support vector machine (SVM), neural network (NN), and decision tree (DT) models for predicting hotel cancelations. However, they are yet to address the class imbalance problem that exists in the prediction of hotel cancelations. In this study, we have shortened this gap by introducing an oversampling technique to address class imbalance problems, in conjunction with machine learning algorithms to better predict hotel booking cancelations. A c... [more]