Discrete Transfer Research Articles

Prediction of carbon capture and sequestration (CCS) technology in a 125 MW tangentially coal-fired subcritical thermal power plant for retrofitting in Bangladesh

The main objective of this study is to assess the use of carbon capturing and sequestration (CCS) technology in the existing plant to reduce the emissions leading to retrofitting. A typical 125 MW tangentially coal-fired Barapukuria Thermal Power Plant (BTPP), Bangladesh has been scrutitinized considering air-firing (existing) and five different oxy-firing (OF) cases have been numerically investigated. For predicting the particle flow, radiative heat transfer and turbulence effects, discrete droplet method (DDM), discrete transfer radiation method (DTRM) and k–ϵ model is considered respectively. For homogeneous reaction for the devolatilization and heterogeneous reactions for the char oxidation process, a two steps reaction mechanism is considered. Model has been validated by comparing the predicted flue gas temperature against the plant data at different positions of the furnace and reasonable agreement have been observed. This study assessed the flow characteristics, thermal behavior and species generations of the selected plant under 80% fuel loading. It is predicted that with the increase of cases from air-firing, level of oxiding elements are increasing in the main combustion zone due to enriched O2 level leading to complete combustion of the particles. It is also found that for OF 31 case, level of CO2 is close to the air-firing case. it has been found that wall temperature is comparatively higher for 100% loading and comparatively lower for 50% loading for almost all similar type of air or oxy-firing conditions. For 100% load, the wall temperature has been reached around 2900 K for OF31 case. It is predicted that air operation equivalent to oxy-firing have been found at < OF 30+ % (Flame temp), at = OF 30+ % (Convec Heat transfer) and at > OF 30+ % (radiative Heat transfer) respectively.

Simulating satellite urban land surface temperatures: sensitivity to sensor view angle and assumed landscape complexity

Urban land surface temperature (LST) from satellite earth observation (EO) varies with sensor view angle. Where these variations are not accounted for, urban LST products are inconsistent through time, limiting their use in urban weather and climate model evaluations and process studies (e.g. urban heat island, building energy balance, human thermal comfort). Obstacle-resolving numerical models (ORM) of urban form and radiation exchanges are being used to: (a) understand relations between EO view angle, the 3-dimensional urban surface, and the surface temperatures from urban land surface models, and (b) evaluate parameterisations (parametric models) that aim to account for LST angular effects for the next operational satellite products. Most ORM are limited to simplified buildings (e.g. cuboids) and surface temperatures by lack of datasets. Novelly, we use both a realistic urban form model and observed surface temperatures to assess the impact of simplifying the urban form and temperature on the modelled LST anisotropy. We test various sets of assumptions in central London by combining ground-based thermal camera observations and the state-of-the-art Discrete Anisotropic Radiative Transfer (DART) model. The high resolution realistic model (< 1 m) includes thermal (surface temperatures varying by sun-surface geometry, shadow history and materials every 30 min) and geometry (sloped roofs, chimneys and vegetation) data. These data are used to simulate brightness temperatures of EO pixels to quantify LST view angle variations.During daytime, a change of view angle of 47° off-nadir corresponds to a difference in LST of up to 5.1 K for the realistic building model. The intermediate-complexity landscape (easily obtainable building geometry/footprints and more idealised surface temperature distributions driven only by shadow patterns) gives the best agreement in simulated LST to the realistic landscape. The directional variations are still captured in total (daytime mean absolute error 0.44 K) when using an idealised ORM representation of the same landscape (cuboid buildings, simplified surface temperature) except for roofs which are near-isotropic. Results suggest that geometry assumptions used in current ORM are suited for evaluation of parametric models used to develop and verify operational LST sensor view angle corrections. Future work should consider more realistic materials and scattering processes including low emissivity glass and metals with challenging specular properties.

Simulation study of a box type solar cooker for different locations

Solar cooker which relies on solar energy can be a viable alternative for the reduction of pollution during the combustion of biomass during the cooking process. The emission from biomass contains hydrocarbons as its major source. This simulation study of box type solar cooker performed using ANSYS Fluent version R1 2022 helps in optimizing the design of solar cooker to predict solar heat flux values for different locations such as Chennai, Vellore, Karur and Rameswaram for a particular day and particular time intervals such as 9 am, 12 pm, 2 pm, 5 pm. The proposed work further highlights the region where the solar cooker can be efficiently used by utilizing non-conventional energy sources for cooking process. In the simulation process, Discrete Transfer Radiation Model (DTRM) was used for tracking the solar radiation and solar calculator to predict the direct and diffuse solar irradiation for a particular day, by considering the latitude, longitude and Greenwich Mean Time (GMT) for specified locations. The specified geographical regions are plotted in a spatial map with solar radiation data obtained from Indian Meteorological Department (IMD) through ArcGIS geospatial techniques. The maximum solar heat flux values obtained at 12 pm, in the simulation results are 718 W/m2, 698 W/m2, 726 W/m2 and 720 W/m2, it is identified that among the four regions karur recorded the highest solar heat flux value of 726 W/m2. The minimum solar heat flux values at 5 pm are 215 W/m2, 202 W/m2, 265 W/m2 and 230 W/m2. Vellore was observed to have the minimum solar heat flux value of 202 W/m2. Solar radiation data obtained from the solar calculator and IMD radiation data were in good agreement with each other with a maximum error percentage of 2.36% because of the variation in the sunshine factor.

Natural interconnections of ecosystems in wildlife

The article reflects the results of the analysis of mutualistic relationships in wildlife in the context. Examples of mutualism in wildlife are found everywhere. Mutualistic connections are considered in the work on the example of lichens (fungus and algae connection) and intestinal microbiota with the human body. The species diversity of lichens is quite large, as is their habitat, which is achieved due to the advantages that the mutualistic relationship provides. A striking example of mutualism Examples of mutualism among predators are much less common. The mutualistic interactions considered in the work clearly demonstrate that it is necessary to consider natural relationships in wildlife from the point of view of a systematic approach, comprehensively and voluminously. Since the components form an interconnected system, it is necessary to study and understand them in relation to network interaction, and not in isolation or in a limited subset of the system. It can be concluded that the network is, in fact, more than just a metaphor, it recognizes the inherent interconnectedness of ecosystem interactions. Networks consist of a set of objects with direct transactions (connections) between these objects. Although the exchange is a discrete transfer, these transactions, taken as a whole, connect the direct and indirect parts into an interconnected web, giving rise to a network structure. Thus, it is quite appropriate to consider interconnected systems as networks because of the powerful exploratory advantage that can be gained by using network analysis tools: graph theory, matrix algebra, and simulation, to name but a few.

Static and Dynamic Compliance Analyses of Curved-Axis Flexure Hinges: A Discrete Beam Transfer Matrix

Abstract A discrete beam transfer matrix method is introduced to enhance the existing approaches for the static and dynamic compliance solutions of curved-axis flexure hinges with variable curvatures and nonuniform profiles. An idea of discretizing curved-axis flexure hinges as a series of constant beam segments parallel to the centroidal axis is developed. As a result, only a concise beam transfer matrix with decoupled longitudinal and transverse components is needed to establish the compliance model. A step-by-step modeling procedure with simple formulas is provided as well qualifying for curved-axis and folded hinges. With this modeling idea, the small-deflection compliance matrix in the common sense of statics and particularly in a viewpoint of frequency-dependent dynamics can be simultaneously obtained. A typical curved-axis flexure hinge available in the literature is analyzed and compared as a study case. In addition, the static and dynamic design for a compliant guiding mechanism composed of folded flexure hinges is efficiently implemented with the presented method.

Iterative Feedback Tuning of Model-Free Intelligent PID Controllers

In the last decades, model-free control (MFC) has become an alternative for complex processes whose models are not available or are difficult to obtain. Among the model-free control techniques, intelligent PID (iPID) algorithms, which are based on the ultralocal model parameterized with the constant α and including a classical PID, are used in many applications. This paper presents a new method for tuning iPID controllers based on the iterative feedback tuning (IFT) technique. This model-free tuning technique iteratively optimizes the parameters of a fixed structure controller using data coming from the closed-loop system operation. First, the discrete transfer functions of the iPID are deduced, considering the first and second order derivatives of the output variable from the ultralocal model. Using the discrete transfer functions, the iPID controllers become the fixed structure type, and the IFT parameter tuning method can be applied. Thus, in addition to the classical gains of the PID algorithm, the value of the parameter α is also obtained, which is usually determined by trial-and-error. The performances of the IFT-tuned iPID controllers were experimentally tested and validated in real-time using Quanser AERO 2 laboratory equipment with a one degree of freedom (1-DOF) configuration.

ВИЗНАЧЕННЯ ПАРАМЕТРІВ ТИПОВИХ ЦИФРОВИХ СТАТИЧНИХ РЕГУЛЯТОРІВ ПРОМИСЛОВИХ ЕЛЕКТРОПРИВОДІВ

The paper is devoted to the development of an analytical method for determining the settings of typical digital static regulators of industrial electric drives, which can be represented as discrete transfer functions in the Z-transform. It is offered to define parameters of adjustment of static regulators, proceeding from the set static error (statism). The possibility of technical realization of the digital proportional-differential regulator with an ideal digital differentiator is substantiated. Significant improvement of system performance indexes when using the differential component of a digital static controller is shown. References 10, figures 7.

Rapid freezing of ground meat: Discrete heat transfer

The paper deals with the optimum conditions for quick freezing of ground meat by continuous and discrete heat transfer. We constructed curves of temperature changes and heat flux during quick freezing of semi-processed meats (ground beef). It was revealed that an increase in the heat flux and a reduction of freezing period by about 1.4 times occurs when the temperature of the cooling medium decreases from -20 С to -40С at air speed of 6 m/s. Comparative characteristics of the change in the freezing duration and the speed of the process by continuous and discrete heat transfer methods are shown. It is proved that with discrete heat transfer, the freezing period lasts 20 minutes, with continuous heat transfer it takes 26 minutes. The paper presents a thermograph and the kinetics of heat transfer during freezing under discrete mode conditions. The quality indicators of ground meat are considered depending on the conditions of heat transfer, as well as the change in the physical and chemical properties of the food after freezing and during storage.

Optimizing the Protocol of Near-Surface Remote Sensing Experiments Over Heterogeneous Canopy Using DART Simulated Images

Optical canopy models that connect land surface properties and satellite-observed radiance must be validated before being used. These models include the bidirectional reflectance distribution function (BRDF) models in the visible and near-infrared domains, and directional brightness temperature (DBT) models in the thermal infrared domain. Near-surface experiments have been extensively conducted to evaluate the modeling accuracy, including ground-, tower-, and aircraft-based measurements. Indeed, it should be noted that in situ measured BRDF/DBT results are sensitive to the experiment protocol, such as sensor moving orientation, flight height, and sampling frequency. A practical tool for optimizing the in situ measurement protocols is needed in the community of remote sensing modeling. For that, we devised a virtual experiment framework based on the discrete anisotropic radiative transfer (DART) 3-D radiative transfer model that is capable of simultaneously simulating both the BRDF/DBT pattern and the images acquired by in situ cameras. Here, as an optimization case, we use it to determine the optimal sensor flight orientation over heterogeneous vegetated canopies (a row-planted scene with three solar angles and a discrete scene with three solar angles) for measuring their DBT distribution. Results showed considerable errors (i.e., image-extracted DBT minus DART-simulated DBT) exist for sensor flight orientation along the canopy rows ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$R^{2}$ </tex-math></inline-formula> = 0.24 and root mean square error (RMSE) = 4.32 K), and they become much smaller ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$R^{2}$ </tex-math></inline-formula> = 0.94 ~ 0.98 and RMSE = 0.82 ~ 1.03 K) in other typical orientations (e.g., cross row plane, solar principal plane, and cross solar principal plane). The critical azimuth offset relative to the row direction that can ensure an acceptable RMSE < 1 K is quantified as atan(3*Unitwidth/Scenesize) based on a series of intensive simulations by this new tool. However, the RMSE of the discrete scene is not sensitive to the flight orientation. Such accuracy differences in various protocols were experimentally verified over row-planted maize using a 4-D tower in Huailai, Hebei, China. The result highlights the great potential of this newly designed DART-based virtual experiment to optimize near-surface experiment protocols.

Определение дискретной передаточной функции приведенной непрерывной части цифровой следящей системы

Предложен способ вычисления коэффициентов дискретной передаточной функции, не требующий трудоемкого получения описывающих их аналитических выражений. Способ основан на совпадении значений переходной характеристики дискретной приведенной непрерывной части и дискретных значений переходной характеристики непрерывной части (НЧ). Последние можно вычислить любым известным способом. Разработан алгоритм вычислений, позволяющий по заданным постоянным времени НЧ и периоду дискретизации рассчитать значения дискретной передаточной функции при единичном коэффициенте преобразования. Приведен пример составления Matlab-программы вычислений. Применение программы дало результат, совпавший с расчетом по формулам, полученным классическим методом.

A coupled discrete-finite element model for bulk materials transfer simulation and PDSS structural wear prediction

The transfer dispatch of bulk materials has been widely used in industrial and agricultural production. When applied to energy extraction and utilization, the interaction of bulk with structures causes problems such as structural wear and dust pollution during the transfer dispatch process. To address the difficulty of dynamic data collecting and monitoring in this process, a multiphase data fusion simulation approach for discrete material transfer dispatch of the digital twin system is proposed. Discrete Element Method (DEM) is used to obtain the movement of bulk material in the Powerless Dust Suppression System (PDSS) structure and its force data on the structure. With this method, this force data is loaded onto the structure for calculation based on Finite Element Method (FEM) more accurately compared to the traditional method. Under the experimental conditions, the maximum stress and strain in the PDSS structure are 34 MPa and 1.55 mm. Moreover, the numerical distribution of stress and strain is relatively continuous, and there is no sudden strong impact. The results show that the method can provide an effective solution to analyze the interaction between the bulk and the structure, and can assist in predicting the structure wear and managing the operating environment in the digital twin system.

Relative stability analysis for robustness design of real-time hybrid simulation

Stability is a prerequisite of a successful real-time hybrid simulation (RTHS), which depends on the time-integration algorithm, the delay-compensation method, the loading system dynamics (mostly characterized as a time delay), and the nonlinearity of the structures being tested. The existing stability analysis methods generally provide a qualitative judgement based on one or some of the factors above, without considering all these factors to estimate quantitative stability margin. However, it is critical to design a robust RTHS system with enough stability margin (i.e., robust RTHS system) to ensure the success of the actual test with inescapable uncertainties. To this end, a relative stability analysis method for robustness design of RTHS systems is proposed. In this method, the critical gain of the stiffness of an experimental substructure is used to quantify the stability limit, and the critical delay is used to quantitatively represent the sensitivity of an RTHS system to the phase discrepancy at the interface. The RTHS system with a nonlinear experimental substructure is modeled by a discrete transfer function in an incremental form, wherein the time-integration algorithm, the delay-compensation method, the loading system dynamics, and the nonlinearities of the experimental substructure are considered. The critical delay and gain are obtained from the discrete transfer function. Two relative stability criteria are proposed based on the critical delay and the critical gain of an RTHS system to facilitate the evaluation of the system's stability performance and the design of a robust RTHS system. To verify the critical delay and gain estimated using the proposed method, numerical simulation of RTHS systems was carried out first. Then RTHS experiments of single-degree-of-freedom models with experimental substructures consisting of a linear spring and a nonlinear stiffness hardening specimen were conducted. The consistent results of the numerical simulation and the physical RTHS tests with those derived from the proposed relative stability analysis method demonstrate its effectiveness and accuracy in determining the stability properties of RTHS systems, which can be further utilized in designing more robust RTHS testing systems.

Unconditional superconvergence analysis of two modified finite element fully discrete schemes for nonlinear Burgers' equation

In this paper, two modified nonconforming finite element fully discrete schemes are considered for solving the nonlinear Burgers' equation. The schemes are constructed by using the nonconforming Wilson element approximation in space combining with the backward Euler(BE) and 2-step backward differentiation formula (BDF2) respectively in time. We present the superconvergence results of the two proposed schemes in modified energy norm of order O(h2+τ) and O(h2+τ2), where h and τ are the space subdivision parameter and time step respectively. The proof involves the time-space error splitting technique, the discrete embedding inequality, the technique of taking difference between two time, the discrete derivative transfer technique and a new modified projection operator. Our analysis not only gets rid of the restriction between temporal and spatial step sizes, but also provides one order higher error estimate results than that of corresponding traditional finite element fully discrete schemes. Finally, numerical experiments are carried out to demonstrate the effective of theoretical analysis.

Passivity-based Analysis of the ADMM Algorithm for Constraint-Coupled Optimization

We propose a novel, system theoretic analysis of the Alternating Direction Method of Multipliers (ADMM) applied to a convex constraint-coupled optimization problem. The resulting algorithm can be interpreted as a linear, discrete-time dynamical system (modeling the multiplier ascent update) in closed loop with a static nonlinearity (representing the minimization of the augmented Lagrangian). When expressed in suitable coordinates, we prove that the discrete-time linear dynamical system has a discrete positive-real transfer function and is interconnected in closed loop with a static, passive nonlinearity. This readily shows that the origin is a stable equilibrium for the feedback interconnection. Finally, we also show global asymptotic stability of the origin for the closed-loop system and, thus, global asymptotic convergence of ADMM to the optimal solution of the optimization problem.

Discrete heat transfer model with space–time nonlocality

The study of processes occurring under locally non-equilibrium conditions is of great interest due to the intensive development of laser technologies and the emerging opportunity to carry out technological operations under extreme conditions (at ultrahigh temperatures, pressures and their gradients). This paper presents the results of the development for a discrete mathematical model of thermal conductivity that takes into account the inertia of the heat transfer process in solids. A computational algorithm using the APDL language has been developed on the basis of the finite element method. APDL (ANSYS Parametric Design Language) is a scripting language that you can use to automate common tasks or even create your own model expressed in terms of parameters (variables). Developed algorithm allows one to automatically calculate temperature fields in solids of arbitrary geometric shape taking into account the heat transfer inertia. The APDL algorithm is adapted for the ANSYS software product which makes it available to a wide range of users. Verification of the algorithm developed is performed by comparing the obtained numerical results with the exact analytical solution of the model task.

Vectorial discrete ray tracing approach for solving radiative transfer in irregular variable index media via discrete transfer method

A novel vectorial discrete ray tracing approach is applied for tracking the curve paths of radiative beams through the variable index media with complex geometries. In this approach, the irregular solution domain is discretized by a boundary-fitted grid, where the radiative properties, including the refractive index, are considered to be constant for each control volume and control surface. Radiative beams travel along straight lines through each volume element until they hit the interfaces between adjacent volume elements, where the direction of rays changes according to the Snell's law of refraction. The radiation heat transfer in absorbing, emitting, and isotropically scattering media is solved by the discrete transfer method. The problem is solved for one-, two-, and three-dimensional media. Axisymmetric media are simulated by detaching a sector with specular sidewalls. Verification is done by comparing the results with available benchmark solutions in literature. For the cases where the data is not available, the accuracy is proved by satisfaction the energy conservation criterion.

Coupling Modeling and Adaptive Control for Piezoelectric-Actuated Positioning Stage

In this paper, a nonlinear coupling model with hysteresis, dynamics, and creep is proposed to describe accurately the complex characteristics of piezoelectric-actuated positioning stage, where a classic Hammerstein model in series with a fractional-order model is given. The fractional-order model is presented to express the nonlinear creep characteristics. Firstly, the Hammerstein structure model is composed of two blocks, where the former block is the classical PI model to describe the static hysteresis effects, and the latter block is the second-order discrete transfer function model to characterize the dynamic characteristics. In addition, the parameters of the coupling model are identified. Secondly, based on the built model, the inverse of fractional-order model and the inverse of PI model are implemented as the feedforward compensations, and an adaptive control is designed to adjust the tracking performance of the whole system. Finally, the effectiveness of the proposed coupling model and controllers are verified by the piezoelectric-actuated positioning experiment stage. Experimental results show that the established coupling model can accurately characterize the hysteresis, dynamics, and creep properties of the stage. Also, the results show that the tracking error is less than 0.8% at low frequency and mixed frequency.

Indirect energy transfer channel between fast ions via nuclear elastic scattering observed on the large helical device

An energy transfer phenomenon between energetic ions, which cannot be explained only considering the Coulomb scattering process, was observed on a large helical device (LHD). This phenomenon often occurs in fusion reactivity enhancement and fast-ion slowing-down process that can be observed as a delay in the decay time of the D(d,n)3He neutron generation rate. The transferred energy required to induce such a reactivity enhancement or delay in the fast-ion slowing-down time (neutron decay time) was examined based on the Boltzmann−Fokker−Planck analysis in which a discrete energy transfer process, called nuclear elastic scattering (NES), is included. It was shown that even though the cross section of the NES is smaller than that of the Coulomb scattering, enough knock-on population appears in the energetic region in ion distribution function to induce the observable NES effects; thus, enough energy is transferred from beam ions to fast component of bulk ion distribution function indirectly and the transferred energy per unit time via NES is comparable to the Coulomb scattering rate. This study analytically demonstrates that the observed phenomena on LHD can be explained smoothly by considering the alternative indirect energy transfer channel between energetic ions, which can be comparable with the one via Coulomb scattering.

Even sampling photonic-integrated interferometric array for synthetic aperture imaging.

To improve the effectiveness of spatial spectrum sampling for the photonic-integrated interferometric imaging, an array forming scheme is proposed with evenly distributed interferometric baselines, which is referred to as the even sampling photonic-integrated interferometric array (ESPIA). The subaperture array of ESPIA is configured as equi-spaced concentric rings. The subaperture beams are coupled and transmitted to the photonic integrated circuit through fiber optic channels and paired into baselines by the interferometric beam combination. The characteristics of ESPIA are analyzed with the discrete modulation transfer function (D-MTF) and multi-resolution mutual information (MR-MI). The simulation results show that it can realize the even sampling coverage of spatial spectrum effectively. With the same scale of synthetic aperture and subaperture array, it can also improve the capabilities of information acquisition for the interferometric array.

Scalar thermal radiation using the adding-doubling method.

The scalar radiative transfer equation in the presence of thermal radiation source is solved in detail, using the adding-doubling method; Planck functions within any given layer are assumed to possess constant, linear, or exponential parameterizations with optical thickness. The radiance profile in any zenith direction is calculated directly in terms of matrix inversions. The inputs to the model are the inherent optical properties (layer total single-scattering albedos, scattering phase functions, and optical thickness) along with temperature and altitude profiles, and the top of the atmosphere and ground surface boundary conditions. The algorithm is implemented in a state-of-the-art MATLAB program, with the cosmic microwave background as the source at the upper boundary and a Lambertian surface reflection at the lower boundary. The simulations are validated against the VLIDORT discrete ordinate radiative transfer model. Results are compared in detail for cases with linear and exponential Planck function parameterizations.