Complete Mathematical Model Research Articles

Boosting the air conditioning unit performance using phase change material: Impact of system configuration

Boosting the energy efficiency of air conditioning (AC) systems will considerably impact on lowering domestic power consumption. Innovative methods are being developed to enhance AC performance. One promising method involves integrating phase change materials (PCM) with the AC systems. The significant PCM charging period is a primary limitation of coupling AC systems with PCM in the previous research. The current study aims to investigate the impact of coupling an AC unit with various PCM container configurations (e.g., parallel plates, staggered and aligned tubes, and elliptical tubes) on PCM charging and discharging, and AC performance. During the nighttime, the low ambient temperature is charged inside the PCMs. Then, during the daytime, the hot ambient air is cooled by passing through the cold PCM heat exchanger before passing over the unit condenser. A complete dynamic mathematical model for the proposed system is constructed and solved numerically using ANSYS software. Results indicate that applying the cylindrical arrangement lowers the solidification time of the PCM at night by approximately one-third compared to the plate arrangement. Also, raising the inflow air temperature of the air-PCM heat exchanger increases the air temperature difference through the heat exchanger and saving percentage of the AC's power and decreases the PCM's charging and discharging time. For inflow air temperatures of 318.15 K, 313.15 K, and 308.15 K, the maximum average percentage of saved power is around 25 %, 18.7 %, and 12.5 %, respectively for 2 h working and around 8.4 %, 7.2 %, and 6.3 %, respectively for 8 h working of the AC unit. Cylindrical configuration is preferable for daily use of AC systems as the charging process can be achieved through the nighttime.

Radiotherapy Complete Mathematical Demonstration for Biological Tumor Control Cumulative Probability Integral Equation Model with Applications

The complete mathematical biological Integral Equation Model (IEM) for Tumor Control Cumulative Probability (TCCP) development and demonstration is explained. Results for algebraic variables change to obtain a suitable Tumor Control Probability (TCP) in convolution at IEM for getting an analytic solution is detailed step by step. Results comprise estimates with further explanations. Solutions for algebraic variable changes to make the Integral Operator analytically solved are demonstrated. Applications in Radiotherapy Treatment Planning Optimization (TPO) with biological Linear Quadratic Model based on 2D [ α and β biological modelling parameters ] are explained.

Photovoltaic Energy Conversion System Integrated Into Unbalanced Distribution Electrical Networks Through Hardware in the Loop

In this article, a real-time, hardware in the loop (HIL) and experimental photovoltaic energy conversion system (PVECS) integrated into unbalanced distribution electrical networks is presented. Commonly, the three-phase voltages are not balanced, because the input–output of single-phase loads in low and medium voltage networks. In this context, the photovoltaic (PV) systems integration under the dq0-Frame control operation scheme, tend to generate current deformations. In contrast, a new control technique for PVECS interconnection is validated in a HIL scheme, even in the presence of unbalanced voltage. This new technique is considered simple and easy to implement, since it consists of a single PI control loop, guaranteeing reliable operation under unbalances voltage events. Thus, preserving favorable characteristics, such as: 1) always balanced currents; 2) low harmonic distortion; 3) unit power factor; and 4) Compliance with the rules of the network code. The PVECS effectiveness is assessed by complete mathematical model, the simulation results are evaluated using MATLAB-Simulink (MATLAB r2018, Mathworks, Natick, MA, USA), and the experimental results are validated with a small-scale prototype operating in a HIL environment and the real-time simulator Opal-RT Technologies (Montreal, QC, Canada); integrating a power capacity of 15 kW in distribution networks.

Research on Efficient Single-Sided Asymmetric Modulation Strategy for Dual Active Bridge Converters in Wide Voltage Range

For the problem of narrow soft-switching range and low efficiency of dual active bridge (DAB) converter in wide voltage range, this article proposes a single-sided asymmetric duty modulation (SSADM) strategy, which contains only two control degrees of freedom, and significantly improves the soft-switching performance and efficiency at light load. First, the potential advantages of asymmetric duty modulation (ADM) method are described through waveforms. The principle of determining which full bridge to adopt the ADM is given and the working principle of SSADM is described. Second, a linear pulse logic combination analysis of SSADM in time domain is performed to establish a complete steady-state mathematical model. To solve the analytical expression for the optimal solution of SSADM, the peak-to-peak value of the inductor current with simple expression is chosen as the optimization objective, and the global optimal solution of SSADM is solved based on the Karush–Kuhn–Tucker (KKT) condition, and the voltage closed-loop control strategy of SSADM is presented. In addition, the soft-switching range of SSADM is analyzed. Finally, the experimental platform of DAB converter based on SiC device is built. Compared with other modulation strategies, SSADM shows better soft-switching performance with significant efficiency improvement, which is verified by the experimental results.

Data organization in laser-based powder bed fusion for metals

Data analytics (DA) and artificial intelligence (AI) have been chosen as the technologies for extracting new knowledge and making better decisions in additive manufacturing (AM) processes. They have been chosen because accurate and complete physics-based, process-simulation or mathematical models do not exist. DA and AI models should be based on measurable data collected by part and process sensors. This paper is focused on how to organize the data collected from such sensors. An example is also provided to show how to store AM-related data in a hierarchical data structure that is consistent with the data from multiple sensors. The data provides functions and properties at various stages in a product lifecycle. The associated metadata for both functions and properties are organized in the same hierarchical structure according to the relationships of machine, build, melting laser beams, process planning, in-situ monitoring, ex-situ inspection, material microstructure imaging, and mechanical testing. Sample data with metadata are stored in a file in the format of Hierarchical Data Format 5 (HDF5). The paper provides an organization of complex AM data that can support AM software tools for a variety of product lifecycle activities.

Computational fluid dynamic study on the adsorption-based desalination and cooling system

Adsorption desalination (AD) is a potentially competitive alternative for potable water production. Unlike traditional rectangular fins for finned-tube adsorbent bed in the AD system, in this study, bullet- and umbrella-shaped fins are employed in the adsorbent bed to improve the heat and mass transfer characteristics in the adsorption/desorption processes, thus augmenting the system performance. Based on a complete transient mathematical model incorporating a three-dimensional computational fluid dynamic model for adsorber and lumped models for evaporator and condenser, impacts of fin configurations regarding base diameter, tip diameter, and shape factor on system performances considering the adsorbent and the whole bed are comprehensively analyzed. Results reveal that a larger base and tip diameter with a lower shape factor contribute to specific bed productions. The underlining relationship between fin configurations and overall performance (total daily water production, total cooling power, and coefficient of performance) is further explored via machine learning. And the optimal fin shape is identified by the genetic algorithm. The optimal base diameter, tip diameter, and shape factor are 0.262, 0.517, and 4.20, respectively, which render a total water production of 5.20 m3/day with a total cooling power of 0.149 kW and coefficient of performance of 0.855.

Research on Game Theory of Air Traffic Management Cyber Physical System Security

For the air traffic management cyber physical system, if an attacker successfully obtains authority or data through a cyber attack, combined with physical attacks, it will cause serious consequences. Game theory can be applied to the strategic interaction between two parties, especially if the two parties have different goals. The offensive and defensive game process of the air traffic management cyber physical system is a non-cooperative and incomplete information dynamic game. The attacker can choose to camouflage the type of attack launched. The attack detection device configured in the system has a certain probability that the attack type can be successfully detected. According to the type of attack detected, the defender updates the posterior belief of the attack type and selects the corresponding protective strategies. According to the game process of offense and defense, a dynamic Bayesian game model of the air traffic management cyber physical system is established, the possible perfect Bayesian Nash equilibrium and its existence conditions are solved, and a complete mathematical model is constructed. The analysis shows that the dynamic Bayesian game model of the air traffic management cyber physical system can help the system defender to quickly obtain an equilibrium strategy and reduce the loss of the system as much as possible.

Hydrogen production from water electrolysis driven by the membrane voltage of a closed-loop reverse electrodialysis system integrating air-gap diffusion distillation technology

Air-gap diffusion distillation (AGDD) technology is one of attracting desalination technology, which can be used to convert various of low and medium grade thermal energies to the salinity gradient energy (SGE) between two electrolyte solutions at different saline concentrations. The SGE is harvestable and converted to the electromotive force of a reverse electrodialysis (RED) stack. The accumulated voltage by several repeated RED units is capable to driving the electricity or hydrogen production apparatus. This paper proposes the complete mathematical model of a RED-AGDD integration system that converts the low-grade thermal energies (LGTE) to hydrogen driven by the membrane voltage sourced from the salinity gradient of KAc solutions for the first time. Accordingly, the influence behaviors of the concentration of concentrated solution (1 mol L−1 to 7 mol L−1), concentration of diluted solution (0.001 mol L−1 to 0.22 mol L−1), solution flow rate of (0.2 cm s−1 to 1.6 cm s−1), solution temperature (303.15 K to 333.15 K), and hydrogen production schemes (three cases) on hydrogen production performances are simulated and discussed. The hydrogen production and energy efficiency are achieved to be 3.7 L h−1and 0.84% respectively. It verifies that the direct scheme of hydrogen production possesses the better performance than that of the indirect scheme, and an intermediate battery is applied to improve the performance. Finally, the optimal operating conditions and parameters are obtained and presented.

A Grey Prediction Algorithm for Enterprise Human Resource Management Validity Model Construction and Improvement

With the deepening development of economic globalization and world economic integration, all enterprises are faced with an increasingly complex and competitive living environment. Therefore, it is particularly important to formulate a human resource strategy suitable for the enterprise’s own development to cope with the external challenges and external competition of the enterprise. However, in the current management practice of state-owned enterprises including power supply enterprises in our country, it is rare to make strategic decisions on human resources by applying scientific, effective, and complete mathematical models. Taking construction enterprises as an example, this study combines human resource management, enterprise management, project management, comprehensive evaluation, and grey system and other theories to systematically study the effect of human resource management in enterprises, and finally constructs a suitable evaluation method for construction enterprises, and an assessment model for diagnosing its human resource management status. We provide practical guidance for the management of human resources in construction enterprises, which is conducive to human resource workers to discover existing problems in time and make improvements, give full play to the potential of human resources, and improve the level of human resource management and the value of enterprises.

Mathematical Analysis and Performance Evaluation of the Cell-Free mMIMO Networks Based on Cognitive Relays

The cell-Free massive multiple input multiple output “mMIMO” networks can provide a satisfied performance for the fifth generation “5G” systems and beyond even there are shadowed users or indoor ones. The performance of the cell-Free mMIMO systems was mathematically analyzed and simulated in a lot of previous works. However, this work aims to provide a complete mathematical model and simulation for a cell-Free mMIMO system that applies relays which operate with the cognitive radio theory. The proposed work can provide novel contributions on two axes. Firstly, the relays can improve the coverage performance of a cell-Free mMIMO network especially at shadowed users, indoor users, and the cell-edge ones. Secondly, the cognitive radio can mitigate the interference in a cell-Free mMIMO network. The interference mitigation results in performance enhancement. Therefore, the cell-Free mMIMO network, based on cognitive relays, is studied. The proposed system is mathematically analyzed and simulated. The spectral efficiency “SE” and signal to interference plus noise ratio “SINR” is deduced. They are given in a closed form formula. It can be concluded that the cognitive relays can improve; SINR, SE, and Energy Efficiency “EE” of a cell-Free mMIMO system.

Energy, exergy, economic and environmental (4E) assessment of hybrid solar system powering adsorption-parallel/series ORC multigeneration system

Energy, exergy, economic and environmental assessment is performed for an integrated hybrid solar system powering a multigeneration system. The proposed multigeneration system is integrated parallel/series configurations of organic Rankine cycle (ORC) unit and adsorption chiller under weather conditions of Alexandria-Egypt. The solar subsystem comprises photovoltaic/thermal collectors (PVT) connected in parallel arrangement with evacuated tube solar collectors (ET). The system output aims to provide annual electricity requirements via PVT collectors and the ORC unit and supply cooling requirements during summer via an adsorption chiller for a small building. The hot water output of the solar system is used to drive the ORC unit and adsorption chiller in four configurations; (Conf-1) hot water drives the adsorption chiller, then its output hot water runs the ORC unit (series), (Conf-2) it drives the ORC first, then the adsorption chiller (series), (Conf-3) hot water is divided between adsorption and ORC (parallel), and (Conf-4) hot water drives only adsorption without using ORC unit. Moreover, the impact of the area ratio of the PVT to ET collector and the ORC working fluid and its flow rate on the system performance is investigated. A complete mathematical model is developed for the system components and solved using MATLAB software. The results show that Conf-4 has the best cooling production performance with an average value of 9.6 kW during the summer months and energy efficiency with an average value of 0.3 during August. Conf-1 is the best performing configuration in cooling production of about 5.6 kW average cooling capacity compared to Conf-2 and Conf-3. In contrast, Conf-2 has the best ORC unit performance with a maximum output of 1.2 kW on a typical day in July. Increasing the PVT collector area in the solar configuration negatively affects cooling production but increases electricity production, which augments the system’s overall exergy and energy efficiencies. R600 is the best ORC working fluid compared to R290 and R134a in terms of average ORC power production of about 0.72 kW compared to 0.63 kW for R290 and 0.39 kW for R134a. Conf-1 is found to have the best energy savings of about 50.8 MWh/year and thus the best emissions of approximately 10.06 equivalent tonCO2 per year. The system Payback period is about 9.8, 9.95, 9.9, and 8.45 years for Conf-1 to Conf-4, respectively, proving the system’s economic feasibility.

A parallel finite volume method for incompressible and slightly compressible reactive flows

In this article, a parallel formulation of the finite volume method is presented for solving three-dimensional, turbulent, mixed, reactive, and slightly compressible flows. It can also be used for incompressible laminar/turbulent flows. The method is designed for nonorthogonal meshes, and oscillations caused by the advective terms are treated by a deferred correction technique. The chosen finite volume scheme is cell centered. The studied fluid is a single-phase multicomponent gas with Newtonian behavior. The focus is mainly on gas mixtures with predominance of N 2 $$ {}_2 $$ , since the chemical reaction of greatest interest is the combustion process in the air. The buoyancy is caused by the gradient of the specified mass, which is a function of the temperature and the composition of the gas mixture. The mathematical model uses an approximation for low Mach numbers, describing slightly compressible flows. The coupling between the fluid dynamic equations is given by the nonlinear Picard's method, with the pressure-velocity coupling treatment given by the SIMPLE algorithm (semi-implicit method for pressure-linked equations). The complete mathematical model includes the sensitive enthalpy equation for the conservation of energy. The LES (large eddy simulation) model is used for modeling the turbulence. The chemical reactions are implemented using the EDC (eddy dissipation concept) and the EDM (eddy dissipation model) approaches. The parallel strategy is based on a subdomain-by-subdomain approach, and uses the MPI and OpenMP standards in a hybrid parallel scheme. Compressed data structures are used to store the matrix coefficients.

All-SiC Traction Converter for Light Rail Transportation Systems: Design Methodology and Development of 165 kVA Prototype

The design and development of a high-performance 165 kVA, 750 V DC all-silicon carbide (SiC) traction converter for new generation light rail transportation systems (LRTSs) are described. In the design of the traction motor drive, the efficiency of the overall system is maximized and the line current harmonic content of the traction motor is minimized. A complete mathematical model of the physical system is derived to carry out real-time simulations and proper control of the LRTS on a real rail track. The electrical and thermal performances of traction-type SiC power MOSFET modules are compared with those of alternative hybrid and Si-IGBT modules for various switching frequencies. The implementation of the developed system is also described. The performance of the resulting system is verified experimentally on a full-scale physical simulator as well as for various track conditions. Very promising results for the next generation railway traction motor drives have been obtained in terms of performance criteria, such as very high efficiency, low harmonic distortion of the motor line current, low cooling requirement, relatively high switching frequency, and hence, superior controller performance. The effects of the SiC power MOSFET operation on the insulation of the available traction motors are also examined experimentally. This paper is accompanied by a video demonstrating the experimental work.

A Review of Numerical Research on the Pressure Swing Adsorption Process

The pressure swing adsorption (PSA) process has been considered a promising method for gas separation and purification. However, experimental methods are time-consuming, and it is difficult to obtain the detailed changes in variables in the PSA process. This review focuses on the numerical research developed to realize the modelling, optimization and control of the cyclic PSA process. A complete one-dimensional mathematical model, including adsorption bed, auxiliary devices, boundary conditions and performance indicators, is summarized as a general modelling approach. Key simplified assumptions and special treatments for energy balance are discussed for model reliability. Numerical optimization models and control strategies are reviewed for the PSA process as well. Relevant attention is given to the combination of deep-learning technology with artificial-intelligence-based optimization algorithms and advanced control strategies. Challenges to further improvements in the adsorbent database establishment, multiscale computational mass transfer model, large-scale PSA facility design, numerical computations and algorithm robustness are identified.

Enhanced dynamic performance of grid feeding distributed generation under variable grid inductance

<p>Controlling weak grid-connected systems is very challenging. In transient, frequency and voltage oscillations may lead to voltage and/or frequency stability problems and finally lead to system collapse. During steady-state operation and at the point of common coupling (PCC), voltage degradation and grid voltage background harmonics restrict the inverter's functionality, reduce the power flow capability and cause poor power quality. With weak grid connection, grid impedance variance will contaminate the voltage waveform by harmonics and augment the resonance, destabilizing the inverter operation. In this paper, complete mathematical modeling is carried out and state feedback-plus-integral control is implemented to support the stabilization of the system. The proposed controller is adopted to provide a smooth transient under sudden load change by controlling the injected grid current under different grid inductance values. Furthermore, the proposed control is used to reduce the order and size of the inverter output filter while maintaining system stability. The proposed control has been compared with the conventional proportional integral (PI) controller under different scenarios to validate its effectiveness and to strengthen its implementation as a simple controller for distributed generator applications.</p>

Общий подход к созданию цифровых двойников мобильных канатных дорог на основе мобильных транспортно-перегрузочных канатных комплексов

The article considers the conceptual approach and practical aspects of creating digital twins of mobile ropeways formed by two end mobile transport and reloading rope units based on self-propelled multi-axle wheeled chassis of high load capacity and cross-country ability. The approach is based on a systematic representation and analysis of the design and operating modes of a mobile ropeway. As a consequence, the digital twin is formed as a multilevel hierarchical structure. It combines information mathematical models of various functional purposes and varying degrees of mutual connectivity, which are distributed by levels depending on the degree of complexity and the possibility of their further aggregation into information mathematical models of a higher level. In relation to a typical mobile ropeway, a structural and functional analysis was carried out, on the basis of which its basic components were established, and calculated structural elements (technical devices and systems) were determined, requiring the development of the necessary individual information mathematical models. Approaches to aggregation of several individual models of computational elements connected by common characteristic quantitative parameters of modeling into group information mathematical models, and then into mode and complete information mathematical models of structural and functional components of a mobile ropeway are considered. The system approach considered in the article and the multilevel hierarchical structure of the digital twin developed on its basis are useful and effective from the point of view of ensuring the modularity of creating a digital twin, its modification for mobile ropeways of a different design, the possibility of using previously developed information mathematical models for similar computational structural elements.

Mathematical Modeling of Anodic Oxidation and Cathodic Reduction of Metals Prone to Passivation, Taking into Account the Peculiarities of Heat and Mass Transfer in the IEG under Pulsed Modes

In the work, a variant of mathematical modeling of the solution of the heat transfer problem was developed, analytical analysis of the dependencies of the parameters of technological parameters was carried out to determine the parameters of current pulses that ensure a uniform distribution of current density over the treated surface. A diagram of the stages of constructing a complete mathematical model of the ECDP process (electrochemical dimensional processing) of titanium, aluminum, and their alloys is given. The above equations reflect the theory of mass transfer processes, include the temperature parameter. The limitations of the possibility of carrying out the treatment process are modeled, the peculiarities of formation and development of the gas-liquid layer, changes in its physical properties, and violation of the treatment stability are taken into account. It has been found that to eliminate the processing instability associated with the appearance of turbulence in the electrode reaction zone due to the large gas filling of the interelectrode gap, a series of relationships must be considered DT = f (i, Q, timp) to determine optimal parameters of pulse current.

Analysis of pressure wave signal generation in MPT: An integrated model and numerical simulation approach

Mud pulse telemetry (MPT) is one of the essential means to ensure a high transmission rate of downhole data. Continuous-wave mud pulse has a high transmission rate, strong stability, and outstanding adaptability, the most widely used downhole data transmission mode. One factor that restricts the high transmission rate of downhole data is the quality of the pressure wave generation signal. However, there is a lack of complete mathematical modeling research methods. Based on CFD theory, a numerical model of the integration of pulse generator and upstream and downstream pipelines was established for the first time, as well as the corresponding grid division process, which was to simulate the pressure wave generation and propagation process under drilling conditions, and the sensitivity analysis of parameters was carried out. The results show that the pressure drop curve derived from the thin-wall throttling theory is not the actual pressure wave, so the optimization results have a particular theoretical error. In fact, with the periodic change of the flow area, the upstream and downstream synchronously generate compression waves and expansion waves, which propagate and gradually decay. The amplitude of pressure wave increases with the increase of displacement and density but decreases sharply with the increase of gap height. Meanwhile, the amplitude does not change with the frequency and viscosity, but it aggravates the propagation attenuation of the pressure wave. Moreover, it is observed that the pressure wave is not a perfect sine wave in the case of sinusoidal rotor rotation, which needs further study. The research results of this paper provide a technical means for the optimization of downhole pressure wave generation, transmission, and noise reduction and help improve the transmission rate of downhole data.

Mathematical Model of Frequency Inverter with Autonomous Voltage Inverter

An analytical analysis of the processes occurring in the systems of an electric drive with a frequency converter, which are characterized by discrete, nonlinear properties, is practically impossible. This predetermines the need to use methods of mathematical modeling and mathematical experiment to study the properties of such systems. Purpose of the work: building a model of a frequency converter with formalization in the form of mathematical relationships of the relationships between the variables characterizing its functioning, based on the analysis of physical processes in each of its elements. Mathematical models of each element must be represented by structural diagrams, which are subsequently combined into a common block diagram of the frequency converter in accordance with the method of structural modeling. Research methods: to solve the set tasks, the methods of the theory of electronics and electrical engineering, induction devices and the concept of switching functions were used. Software implementations of the proposed mathematical models and numerical studies of the processes reproduced by them were performed in the MATLAB computing environment (SIMULINK application software package). Results: the method of structural modeling made it possible to create a fairly universal and flexible version of a complete mathematical model of a frequency converter, due to the possibility of a fairly simple inclusion in it of various options for mathematical models of elements included in a specific real frequency converter. In this case, the resulting model preserves the topology of a real frequency converter and the observability of all its real physical variables. The use of the theory of induction devices and the concept of switching functions made it possible, on a single methodological basis, to create physically and mathematically grounded mathematical models of all the main elements of the frequency converter. The constructed model makes it possible to clarify the relationship between the physical variables of the individual elements of the frequency converter and their mutual influence

Metal foam packed adsorbent bed boosting the performance of the adsorption-based desalination and cooling system

Adsorption-based desalination and cooling system serve as an alternative technology to relieve deteriorated water scarcity and energy shortage. In this study, a complete transient mathematical model considering the complete cycle and the dynamics of all components is developed, where the local mass and heat transfer processes in the adsorption bed are solved via the computational fluid dynamics, whose boundary conditions are obtained via solving zero-dimensional energy and mass balance equations in the evaporator and condenser. Based on the proposed model, bed configuration optimization in a metal foam packed bed regarding metal porosity, bed porosity, and metal and adsorbent type is conducted to augment the system production of cooling and water. Results reveal that the optimal system with a metal porosity of 0.8 and bed porosity of 0.25 exhibits a cooling effect of 8.74 kW and potable water of 300 m3 per day. In addition, the effect of advanced asymmetric cycle condition on system throughput is comprehensively explored. The optimal advanced asymmetric cycle conditions for cooling and water productipn are, respectively, identified, where 11.5% improvement in cooling and 11.3% improvement in water production in water production are achieved.