Flow Variables Research Articles

玉米植保无人机离心喷施系统设计与雾滴分布特性试验

Aiming at the problems of spraying pole-type plant protection machines difficult to get down to the field after row closure of maize in the middle and late stages, uneven droplet distribution of pressure nozzle-type plant protection drone, and difficult to change the droplet particle size, this paper designed a UAV centrifugal spraying system for maize planting protection through the designed centrifugal nozzle combined with a plant protection drone. A single nozzle parameter test was carried out to study the relationship between nozzle speed, flow rate and droplet size. The variable parameter flow rate is set in the range of 300 ml ~ 1000 mL / min, and the nozzle rotation speed is set in the range of 8000 ~ 18000 r / min gradient change. The test results show that the droplet size is related to the liquid supply flow rate and the nozzle rotation speed. According to the theory of optimal biological particle size, the centrifugal nozzle parameter is determined to select the liquid supply flow rate of 1000 mL / min and the nozzle rotation speed of 14000 r / min. The droplet distribution characteristics test under the actual operating conditions was carried out with this parameter, and the important index parameters such as droplet size, droplet density and coverage rate were analyzed to characterize the UAV aerial spraying operation. The experimental results show that the flight speed of the UAV has an important effect on the droplet deposition parameters, which significantly affects the droplet coverage, droplet density and deposition amount of the bottom layer of maize, and the droplet coverage and the droplet deposition amount of each sampling layer tends to decrease with the increase of flight speed, and the coefficient of variation (CV) value of the centrifugal spraying system was the smallest at the flight speed of 1.5m/s, and the effect of droplet deposition was the most uniform. at a flight speed of 1.5m/s. The effect of droplet deposition is the most uniform. This study can provide a reference basis for the optimization of parameters and the correct use of centrifugal plant protection UAV in the middle and late stage plant protection operations of tall crops such as maize.

Quantitative index for temporal and spatial patterns of occupant behavior based on VRF big data

The energy consumption required to cool buildings has increased significantly because of occupant behavior. The air conditioning (AC) usage in residential buildings, particularly the part-time and part-space patterns, has a considerable impact on energy consumption. However, the part-time, part-space patterns of occupant behavior, which are characterized by complexity and diversity, present significant challenges when quantitatively assessing their impact on cooling energy consumption. To accurately describe occupant behavior, this study introduces the quantitative index of the part-time, part-space ratio of AC usage. We conducted clustering analysis based on part-time and part-space ratios of AC usage to obtain the typical occupant behavior patterns, user distribution, and cooling energy consumption levels of variable refrigerant flow (VRF) AC systems in various climatic zones of China based on data from 4373 VRF systems across various climatic zones from June to October 2019. The main findings were that the typical occupant behavior pattern of AC usage for residential buildings was the part-time, part-space AC mode, with less than 500 cooling hours and a simultaneous use coefficient below 0.6. The part-time, part-space ratio of AC usage effectively correlated occupant behavior with cooling energy consumption, as evidenced by an R2 value of 0.91, compared with the traditional standard of using the duration of the AC operation. The part-time, part-space ratio of AC usage and cooling energy consumption were higher in the hot summer and warm winter regions than those in the other two climatic zones. These findings can assist in the evaluation of cooling energy consumption for various occupant behavior patterns and provide technical guidance for reducing cooling energy consumption.

The Impact of Promotion, Product Quality, and Trust toward Online Impulsive Buying Decisions: The Mediating Role of Flow Experience

Online purchasing has experienced significant growth, with approximately 40 percent of total online purchases classified as impulsive. However, there is a gap between the potential rise in online purchases and the proportion of impulsive purchases, which remains at 40 percent. To address this gap and boost short-term sales for producers, this study aims to evaluate the impact of promotion, product quality, and trust on online impulsive buying decisions, considering the role of flow experience as an intervening variable. The research employs a descriptive quantitative method, collecting data through questionnaires using a Likert scale. The study was conducted in the D.K.I Jakarta area, involving 246 respondents. Data analysis was performed using path analysis to examine the relationships between the independent variables (promotion, product quality, and trust), the intervening variable (flow experience), and the dependent variable (online impulsive buying decisions). The findings reveal that promotion has a positive and significant influence on online impulsive buying decisions. Moreover, promotion significantly impacts flow experience, which in turn mediates the effect of promotion on online impulsive buying decisions. On the contrary, product quality and trust do not significantly affect either online impulsive buying decisions or flow experience. This suggests that promotional activities are crucial for enhancing impulsive purchases online, while product quality and trust play a lesser role in this context.

Analysis of the scrap pre-heating inside an EOF steel refining furnace

In the present work a full-scale mathematical model of the gaseous flow and the thermal exchange of gases with the scrap were proposed in the exhaust system of an Energy Optimizing Furnace (EOF). The analysis of the flow and heat transfer of the gases in the exhaust system is fundamental to predict the thermal use in the pre-heating of the scrap and the best scrap allocation profile in the system to predict the continuity of the current industrial process. The objective of this work is to improve the overall energy efficiency of the EOF process, thereby reducing the direct and indirect emission of gases that contribute to climate change. Industrial tests were carried out to obtain the real values of the variables such as gas and scrap temperature. The results of the variables were used in the mathematical model. The results of the mathematical modelling demonstrated that the heat transfer between the gases and the metal scrap depends mainly on the previous preparation in the scrap yard and on the control of the size and compaction of the scrap. In this work it was possible to predict the variables of gas flow and scrap pre-heating during the steel production process in the EOF using mathematical simulation and validating with the results collected in the industrial furnace.

Numerical Simulation of Internal Flow Field in Optimization Model of Gas–Liquid Mixing Device

This article studies the influence of structural parameters of the optimization model for the gas–liquid mixing device of a fire truck (compressed air foam lift fire truck, model JP21/G2, made in China) on the liquid phase volume fraction, static pressure, velocity streamline, and the influence of smaller flow rates on the mixing effect. By using the computational fluid dynamics (CFD) software FLUENT 2021 R2, numerical simulations were conducted on the fluid domain model of the gas–liquid mixing device of the JP21/G2 fire truck. The changes in the mixing effect time dimension, liquid phase volume fraction, static pressure, and velocity streamline inside the gas–liquid mixing device were obtained. The optimal mixer structure combination in practical applications was inferred through orthogonal experiments, and the influence of flow rate on the optimal pipe diameter and shortest mixing distance was obtained through variable flow rate simulation experiments. The numerical simulation results show that the presence of bent pipes in the JP21/G2 real vehicle model hinders the gas–liquid mixing process. A straight pipe section of at least 8 m was added after the bent pipe to ensure the mixing effect. The optimal parameter combination for orthogonal experiments had an accurate value of 50°-50°-220 mm. Under the same pipe diameter, using a larger flow rate can achieve better mixing effects.

Influence of hydrological variability and life history strategy on riverine fish assemblages in the Australian wet‐dry tropics

AbstractRiverine fish assemblages are strongly influenced by attributes of the flow regime. Tropical savannah river systems have distinct and predictable hydrologic seasonality, reflecting the wet‐dry climate, but can vary substantially in terms of dry season flow permanency and wet season flow‐pulse characteristics. Understanding how flow permanence and variability influence fish assemblages, and whether these factors can be used to predict responses to future hydrological change, are key knowledge gaps that impede effective management. We examined the influence of hydrological variability on the structure and diversity of freshwater fish assemblages across rivers of the wet‐dry tropics of northern Australia. We found distinct fish assemblages that varied predictably across three hydrological river types: Intermittent, Perennial Stable and Perennial Flashy flow regimes. This distinction emerged despite a common species pool across the region. Species richness was greatest in rivers with Perennial Stable flow regimes, whereas beta‐diversity was greatest in Intermittent rivers. However, life history strategies of constituent species were generally poor predictors of species abundances within each hydrological river type. The distinct fish assemblages evident among hydrological classes may provide some cautious ability to both predict potential fish assemblage changes with future hydrological changes (e.g. if perennial streams became more flashy or intermittent), and to predict fish assemblages expected in unsampled rivers with particular hydrological characteristics. Our findings provide further support for the importance of maintaining regional flow‐habitat heterogeneity and the connectivity between hydrological river types, and their essential role for conserving tropical fish species diversity into an uncertain hydrological future.

The pulse of Yarlung Tsangpo River: Ultra-high-resolution insights into the flow and sediment

Traditional monitoring techniques of flow and sediment are inadequate for the sparsely populated, the rivers in the Qinghai-Tibetan Plateau region which are experiencing amplified climate change. Inspired by the Euchiloglanis fish, this study developed a unique self-contained hydrodynamic observation platform to withstand the high velocities of mountain rivers typically encountered in mountain rivers. The platform, equipped with sensors, was successfully deployed in the Yarlung Tsangpo River, collecting ultra-high-resolution data on flow and sediment over a period of nearly two months. Performance assessments showed that the median value of discharge per unit width measured and suspended sediment concentration by this system were basically consistent with those daily measurements from the hydrological station. Meanwhile, the superiority of the system was reflected in the more significant daily average change, especially at the flooding period. The data unveiled significant minute-level hydrological fluctuations and a complex interplay of factors affecting the river’s flow and sediment transport. A wavelet coherence analysis revealed asynchrony changes in short-period flow and sediment variables. Persistent short-period and coherent long-period signals are significantly displayed during flood events. The platform promises future applications, such as automated benthic observations and replacing traditional ’lead-line’ methods. Despite acknowledging system limitations of underwater attitude, burying tendency, and real-time data transmission capabilities, the study highlighted the crucial role of this system in understanding and managing river dynamics, particularly amid escalating environmental threats.

Obstacle arrangement can control flows through porous obstructions

Previous work suggests that the arrangement of elements in an obstruction may influence the bulk flow velocity through the obstruction, but the physical mechanisms for this influence are not yet clear. This is the motivation for this study, where direct numerical simulation is used to investigate flow through an array of cylinders at a resolution sufficient to observe interactions between wakes of individual elements. The arrangement is altered by varying the gap ratio $G/d$ (1.2 – 18, G is the distance between two adjacent cylinders, d is the cylinder diameter), array-to-element diameter ratio $D/d$ (3.6 – 200, D is the array diameter), and incident flow angle ( $0^{\circ} - 30^{\circ}$ ). Depending on the element arrangement, it is found that the average root-mean-square lift and drag coefficients can vary by an order of magnitude, whilst the average time-mean drag coefficient of individual cylinders ( $\overline{C_{d}}$ ), and the bulk velocity are found to vary by up to $50\,\%$ and a factor of 2, respectively. These arrangement effects are a consequence of the variation in flow and drag characteristics of individual cylinders within the array. The arrangement effects become most critical in the intermediate range of flow blockage parameter $\mathit{\Gamma_{D}^{\prime}} = 0.5-1.5$ ( $\mathit{\Gamma_{D}^{\prime}}=\overline{C_{d}}aD/(1-\phi)$ , where a is frontal element area per unit volume, and $\phi$ is solid volume fraction), due to the high variability in element-scale flow characteristics. Across the full range of arrangements modelled, it is confirmed that the bulk velocity is governed by flow blockage parameter but only if the drag coefficient incorporates arrangement effects. Using these results, this paper proposes a framework for describing and predicting flow through an array across a variety of arrangements.

Utilizing waste heat in wastewater treatment plants for water desalination: Modeling and Multi-Objective optimization of a Multi-Effect desalination system using Decision Tree Regression and Pelican optimization algorithm

This paper examines the feasibility of using waste heat from wastewater treatment plants (WWTPs) for water desalination. A model was developed to utilize waste heat from the gensets at As Samra WWTP in Jordan, using real data and TRNSYS® software to calculate available waste heat. The desalination process was then modeled with ASPEN PLUS® software, focusing on multi-effect desalination (MED). Both series and parallel configurations for the MED system were compared. The study investigated the effects of system feeding flow rate, feeding pressure, and heat input on productivity, performance ratio, and recovery ratio. The study also introduces a novel optimization technique combining machine learning and modern optimization algorithms to maximize system productivity and performance. Initially, a decision tree regression (DTR) model is developed to establish relationships between key independent variables (flow rate, feed pressure, and heat input) and dependent variables (productivity, performance ratio, and recovery ratio). The Pelican Optimization Algorithm (POA) is then used to identify the optimal values of the independent variables for maximum productivity and performance. The results show that using a series configuration yields a system productivity of 3984.2 kg/hr, a performance ratio of 3.78, and a recovery ratio of 0.991 at a feed flow rate of 4000 kg/hr, feed pressure of 3 bars, and heat input of 719 kW. Optimal productivity (4421 kg/hr), performance ratio (3.81), and recovery ratio (0.851) are achieved at a feed flow rate of 5166 kg/hr, feed pressure of 3.2 bars, and heat input of 794 kW. The techno-economic assessment indicates a levelized cost of water of 1.63 USD/m3 for parallel configurations and 1.65 USD/m3 for series configurations, with a payback period of less than two years.

Numerical Investigation of Flow Distribution in PEMFC and Pemwe Stacks Considering Two-Phase Flow in the Stack Headers

PEM fuel cell (PEMFC) and PEM water electrolyzer (PEMWE) stacks are assembled by connecting a series of unit cells. The stack headers are conduits formed by the ports of these unit cells; see Fig. 1(a). The flow field in the headers affects the flow uniformity of the stack, which significantly impacts the stack’s performance and lifespan. This study aims to investigate the fluid flows in the stack headers of PEMFC and PEMWE. A specific objective of this study is to understand how two-phase flow (liquid water and gases) in the headers would impact the flow distribution inside the stacks.The present study investigates the flow inside a stack by two-dimensional (2D) and three-dimensional (3D) models, as shown in Figure 1(b) and (c) respectively. The 3D model was constructed with an inlet header and an outlet header with flow resistors in between to represent the unit cells.1,2 CFD simulations using ANSYS Fluent were performed over a 100-cell PEMFC stack based on the k-ε RNG turbulence model. The two-dimensional 100-cell PEMFC stack model was built with COMSOL Multiphysics and considers the diffusion and transport, proton and electron conduction, electrochemical reactions on the catalytic layer, and heat transfer in the unit cells. The flow distribution obtained from the 3D model was used as the boundary conditions for the 2D model to calculate the effects of flow distribution on the overall performance of the stack. It should be pointed out that in the 3D models of PEMFC and PEMWE headers, simulations using the volume of fluid (VOF) model to track the liquid water droplets in a PEMFC and bubbles in a PEMWE were carried out to gain insights into the impact of two-phase flow on stack header flow sharing.The simulation results show the existence of unstable and highly transient turbulence within the PEMFC outlet header, as seen in Figs. 1(d) and 1(e). Jet flows from individual cells cause vortices inside the header, reducing the effective flow area. Liquid water accumulates on the inner wall of the header and is swept out by the cross-flow. In the dead-end region, liquid water undergoes helical motion under the influence of vortices, resulting in a longer residence time in the header and making it less prone to be expelled. This study parametrically investigated the effects of header size and air stoichiometry. As the cross-sectional area of the inlet header decreases from A=1,225 mm2 to A=857.5 mm2, the coefficient of mass flow variation within the stack increases, indicating a decrease in the uniformity of flow distribution inside the stack, as shown in Fig. 1(f). The air stoichiometry also affects the flow distribution inside the stack; as the air stoichiometry λ decreases from 2.2 to 1.4, the uniformity of gas distribution in the stack deteriorates significantly.The methodology used in the present study provides a reference for the parameter design and operating conditions of PEMFC and PEMWE stacks. It helps to gain insights into the optimization of stack header design and energy management.

Irreversible mechanism and thermal cross-radiative flow in nanofluids driven along a stretching/shrinking sheet with the existence of possible turning/critical points

The significant increase in thermal efficiency and the rate of energy exchange used in fuel dynamics and automobile coolants are leading to a better understanding of nanofluids. This computational analysis explores the thermal conductivity performance for radiative cross-flow of a nanofluid across an expanding/constricting sheet with a suction effect as a result of its application. To compute or calculate the magnificent point of nanofluid flow, the entropy, and asymmetrical heat source/sink effects are also elicited. The boundary layers traverse a stream-wise procedure for expanding and contracting sheets. Additionally, the study examines the features of heat transfer and cross-flow of nanofluids using numerical simulations. By employing similarity variables, the basic PDE equations of the current model are transformed into ODEs, and they are subsequently evaluated using the bvp4c method. Therefore, the effects of embedded flow variables on drag force, heat transfer rate, and entropy generation profiles have been framed using parametric research. Multiple solutions are offered for a specific range of the contracting parameter as well as the mass suction parameter. In addition, the heat transfer rate accelerates due to the heat source and decelerates due to the heat sink. The literature that is already published has been compared favorably, and it reveals many commonalities.

Virtual care for paediatric asthma: A randomized controlled trial.

This work aims to investigate whether virtual care can improve clinical outcomes for children with asthma, similar to face-to-face specialty care. The study used a randomized controlled trial design, with participants allocated to either a virtual care group (n = 47) or a control group (n = 50) using simple randomization. The study was conducted from March to August 2021, and a sample of 97 children with asthma was recruited. Children in the virtual care group received online training in four modules within the first month and support through virtual meetings and phone or video calls, while the control group received standard care. The primary outcome of the study was the Asthma Control Test and Child Asthma Control Test. The virtual care group had significantly better outcomes than the control group in terms of C-ACT scores for children aged 7-11 years, fewer days under 80% of the optimum level of peak expiratory flow, lower peak expiratory flow variability, fewer rescue medication uses, and more symptom-free days. The virtual care group also had a lower number of unscheduled hospital visits and a greater improvement in quality of life compared with the control group. This study demonstrated that virtual care can improve disease management and quality of life for children with asthma.

Squeezing hydromagnetic nanofluid flow between two parallel plates with joule heating effects and induced magnetic field

Over the years, cooling high energy devices has become a major challenge to most industries. Thus, squeezing hydromagnetic nanofluid flow between two parallel plates has garnered alot of attention. In the present study, an unsteady, incompressible, hydromagnetic gold and water nanofluid flow squeezed between two parallel plates with Joule heating and a magnetic field that is induced is considered. The model considers the impacts of Joule heating,Viscous dissipation and induced magnetic field. In contrast with other studies which may have focussed on only one or two of these aspects this comprehensive approach provides a more accurate depiction of the flow pattern. Employing the finite difference method, the flow's non-linear differential equations are numerically solved and then implemented in MATLAB. The effect of changing various parameters on flow variables such as velocity, magnetic induction and thermal profiles are determined and the results obtained are presented graphically. Increasing magnetic parameter and Prandtl magnetic number caused a decline in temperature,velocity and magnetic induction profiles. Further, increasing the Eckert number and Joule heating parameter lead to an increase in temperature profiles. This findings have a direct impact on high-energy cooling devices which frequently experience heat dissipation. Additionally, engineers can ensure optimal performance and the longevity of plate heat exchangers in industries.

Environmental, Geographical, and Economic Impacts of Inbound Tourism in China: A Mixed-Effects Gravity Model Approach

This study examines the dynamics of inbound tourism in China, utilizing a mixed-effects gravity model to analyze data from urban clusters around China’s three major airports. The research methodology of the study includes applying advanced econometric techniques, such as the Poisson pseudo-maximum likelihood estimation, to ensure robust and accurate results. The study focuses on international tourist arrivals and foreign exchange earnings, identifying key drivers such as tourism resources, transportation safety, and service quality. Our findings indicate a 10% increase in per capita GDP correlates with a 0.88% rise in inbound tourist numbers. Additionally, proximity to major urban centers like Beijing, Shanghai, and Guangzhou significantly influences tourist arrivals, with every 100 km increase in distance resulting in a 5.56% decrease in tourist numbers. The study also explores the impact of environmental factors on tourism, suggesting that improvements in green coverage and reductions in industrial waste and traffic fatalities could enhance tourist arrivals. Conversely, environmental protection measures can both positively and negatively impact tourism. This research provides a strategic blueprint for policymakers and professionals in tourism and environmental sustainability, emphasizing the importance of integrated environmental sustainability in tourism development strategies. The model accounts for up to 79% of the variability in inbound tourism flows, offering robust evidence that economic and policy dimensions impact tourism.

A digital twin-based traffic light management system using BIRCH algorithm

Urban transportation networks are vital for the economic and environmental well-being of cities and they are faced with the integration of Human-Driven Vehicles (HVs) and Connected and Autonomous Vehicles (CAVs) challenge. Most of the traditional traffic management systems fail to effectively manage the dynamic and complex flows of mixed traffic, mainly because of large computational requirements and the restrictions that control models of traffic lights directly based on extensive and continuous training data. Most of the times, the operational flexibility of CAVs is severely compromised for the safety of HVs, or CAVs are given high priority without taking into account the efficiency of HVs leading to lower performance, especially at low CAV penetration rates. On the other hand, the existing adaptive traffic light approaches were usually partial and could not adapt to the real-time behaviors of the traffic system. Some systems operate with inflexible temporal control plans that cannot react to variations in traffic flow or use adaptive control strategies that are based on a limited set of static traffic conditions. This paper presents a novel traffic light control approach utilizing the BIRCH (Balanced Iterative Reducing and Clustering using Hierarchies) clustering algorithm combined with digital twins for a more adaptive and efficient system. The BIRCH is effective in processing large datasets because it clusters data points incrementally and dynamically into a small set of representatives. The suggested method does not only enable better simulation and prediction of traffic patterns but also makes possible the real-time adaptive control of traffic signals at signalized intersections. It also improves traffic flow, reduces congestion, and minimizes vehicle idling time by adjusting the green and red light durations dynamically based on both real-time and historical traffic data. This approach is assessed under different traffic intensities, which include low, moderate, and high, while efficiency, fuel consumption, and the number of stops are being compared with the traditional and the existing adaptive traffic management systems.

Multiphase flow analysis of complex wellbore–fracture–cave connections in condensate gas reservoirs

The significant heterogeneity of fracture-caved gas reservoirs and the phase transition behavior with pressure depletion pose great challenges for flow behavior analysis and property estimation. Therefore, the objective of this paper is to develop robust and novel pressure transient analysis models for condensate-gas flow under pressure depletion in fracture-caved gas reservoirs. To characterize the complex connections between wellbore, fracture region, and caves, four conceptual models of wellbore–fracture–cave distributions are determined. The fracture region is considered as a dynamic three-zone (dry gas zone, condensate-gas two-phase zone, and transition zone) to characterize the phase transition during pressure depletion, while a variable storage concept is introduced to describe the phase transition in the wellbore and caves. The results indicate that six typical flow stages can be observed from the type curves: constant wellbore storage flow, variable wellbore storage flow, fracture linear flow (FLS), constant cave storage flow, variable cave storage flow, and transition flow. Moreover, the phase transition behavior in the fracture region is reflected in the changes of one-half slope straight lines during the FLS period, while the phase transition behavior in the wellbore and caves is reflected in the pressure derivative curve as a positive upward bending of the straight line with unit slope at later stage. The property estimation in the fracture-caved gas reservoirs (i.e., length and permeability of the fracture region, the storage coefficient of wellbore and cave) by matching with the actual pressure monitoring data provides a better understanding of the geological evidence.

On-the-Fly Unsteady Adjoint Aerodynamic and Aeroacoustic Optimization Method

An on-the-fly unsteady adjoint-based aerodynamic and aeroacoustic optimization methodology is presented, aiming to achieve practical engineering applications to explore high-efficiency and low-noise design for aerodynamic shapes. Firstly, a novel on-the-fly hybrid CFD-CAA approach is developed with a close integration of unsteady Reynolds-averaged Navier–Stokes equations and a fully viscous time-domain FW-H formulation. Subsequently, an adjoint-based sensitivity analysis method is proposed for unsteady aerodynamic and aeroacoustic problems with either stationary or moving boundaries, wherein a unified architecture for discrete-adjoint sensitivity analysis of both aerodynamics and aeroacoustics is achieved by integrating the on-the-fly hybrid CFD-CAA approach. The on-the-fly approach facilitates direct evaluation of partial derivatives required for solving adjoint equations, eliminating the need for explicitly preprocessing flow and adjoint variables at all time levels in a standalone adjoint CAA solver and consequently substantially reducing memory consumption. The proposed optimization methodology is implemented within an open-source suite SU2. Results show that the proposed on-the-fly adjoint methodology is capable of achieving highly accurate sensitivity derivatives while significantly reducing memory requirements by an order of magnitude, and further demonstrations of single-objective and coupled aerodynamic and aeroacoustic optimizations highlight the potential of the proposed method in exploring high-efficiency and low-noise design for aerodynamic shapes.

The Effect of Operating Cash Flow And Dividend Payout Ratio On Stock Returns of PT. Mayora Indah

Dividend payments that tend to decline in food and beverage industry companies on the Indonesia Stock Exchange have an impact on company performance, which will be reported in the form of financial reports published annually. Financial reports have an important role in reducing the negative view of dividends in investment. This study aims to analyze the effect of operating cash flow and dividend payout ratio on stock returns at PT Mayora Indah Tbk for the period 2018–2021. The research method used is quantitative data with a population of 24 food and beverage subsector companies listed on the Indonesia Stock Exchange and a sample of 1 company with purposeful sampling analysis. The results of the study prove that operating cash flow has no significant effect on stock returns and dividend payout ratio has a significant effect on stock returns, and simultaneously, the operating cash flow and dividend payout ratio variables affect the stock returns of PT Mayora Indah Tbk for the period 2018–2021. This research is a material consideration and input for companies in carrying out policies that can affect stock returns in the company.

Bioconvective variable viscosity flow of Carreau nanofluid with external heat source and nonlinear radiation: Analysis with convective heat and mass constraints

In this study, an unsteady model for Carreau nanofluid with microorganism decomposition is developed. The viscosity and thermal conductivity of the Carreau nanofluid are considered variable. Magnetic and porosity effects are included using a magneto-porosity parameter. An additional heat source is introduced to improve heat transfer. Nonlinear analysis is applied for radiative applications. The flow is modeled using an oscillatory stretching surface. Convective mass and heat constraints are used to analyze the problem. Analytical computations are performed on the developed model. The significance of various parameters for the thermal problem is discussed. The results may enhance the performance of transport problems, heat transmission, energy systems, and thermal devices.

Kinetic Simulation of Nozzle Flow in a Micronewton-Class Cold Gas Thruster

Many scientific space missions need highly precise attitude and orbit control or ultrafine drag compensation, which relies on the variable-thrust propulsion technology operating at the micronewton level. Cold gas thruster (CGT) is a very promising solution, mainly because of its high reliability. One of the keys to the success of micronewton variable-thrust CGT is to understand the flow in its nozzle, whose configuration is much more complex than traditional CGT nozzles. This paper applies kinetic-based multiscale models to investigate the gas flow in the complex nozzle of a micronewton variable-thrust CGT. The simulations reveal that the flow simultaneously experiences all kinds of regimes from continuum to free molecular. The continuum breakdown is likely to occur near the throat region due to large gradients of flow variables and in the expander due to low gas density. Frictional choking is observed, and the nozzle length can be optimized to improve the thruster performance. Nozzle performance measures such as thrust, discharge coefficient, and thrust efficiency are found to change only with the throat Knudsen number Knt. The performance curves can be divided into two sections at Knt≃0.1, and thereby an empirical piecewise formula for thrust prediction is proposed.