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Paper drying is the most energy-intensive step in papermaking and around 90% of the total amount of manufactured paper is produced in multi-cylinder dryers. A framework based on a physical model of multi-cylinder drying was developed to assess the effect of various energy-saving measures at a production site. The framework was applied to the drying section of a paper machine producing corrugated paper. The calculated steam and power savings reach up to 1.55 GJth/tpaper and 0.1 GJel/tpaper respectively, depending on the chosen combination of efficiency measures. The cumulative effect of the measures is not equal to the sum of their individual effects, which highlights the importance of accounting for interactions when considering the implementation of several measures. [ABSTRACT FROM AUTHOR]

Several miniaturized viscometers, or microviscometers, have been developed exploiting numerous rapid prototyping techniques. Among them, paper microstrips, famously known as microfluidic paper-based analytical devices ($\mu $ PADs), have become popular due to their cost-efficacy, simple fabrication, fast response, and easily disposable. Many fabrication methods are existing to develop paper microstrips. Herein, an alternative fabrication method is proposed where fused deposition modeling (FDM)-based 3-D printer (3DP) has been employed using polycaprolactone (PCL) filament. F, image processing has been utilized to measure viscosity in such microfluidic domain. Viscosity was calculated by measuring the time taken by the fluid to cover a fixed length between two spots in the microchannel based on the programed and color-coded regions-of-interest. The image processing program was developed considering the change in the gray scale in the virtual region of interests (ROIs) in the microchannel during the fluid flow in the paper microstrips. A 3-D printed handheld platform, containing raspberry pi with on-board camera and display, was developed to execute the image processing and automate the entire work flow. In the proposed device, the accuracy was measured to be >92%. [ABSTRACT FROM AUTHOR]

It is well established that copper sulfide is formed due to reaction of sulfur with copper conductors in transformers and reactors. However, there is very little experimental evidence to demonstrate copper sulfide diffusion into bulk of paper. Diffusion experiments have been carried out on three samples of kraft paper having different thickness. Positron Annihilation Lifetime Spectroscopy has been used to investigate the possibilities of copper sulfide diffusion into bulk of paper. This study has demonstrated that copper sulfide can diffuse into the bulk of paper leading to either increase or decrease in free volume of paper. The reasons for changes in free volume of paper due to copper sulfide deposits are explained. The consequences of copper sulfide diffusion on PD, voltage-current characteristics under ac and volume resistivity are discussed. Electric field simulation has been used to explain the effects of Cu ions and copper sulfide formation on electric stress distribution across paper. [ABSTRACT FROM AUTHOR]

Oil-paper insulation ageing of transformer has characteristics of spatial locality due to uneven temperature distribution. The transformer is sealed, it is difficult to obtain the local ageing state of oil-paper insulation by sampling directly. Currently, there are no effective detection method to detect the insulation state of local regions. The oil-immersed paper resistivity inversion method can nondestructively assess the local state of oil-paper insulation. However, the current inversion methods still have shortcomings and need to be improved. In this paper, combining the back propagation neural network (BPNN) and Newton downhill method (NDM), an improved inversion method is proposed to optimize the current inversion method, so as to reduce the effect of initial value on it and make calculated results converge better. Finally, a 3D 10 kV transformer model is established to verify the effectiveness of the proposed method. The resistivity calculated by the improved method show that the method can provide initial resistivity values for technicians and improve the convergence and accuracy of current inversion method, which is more suitable for extending to the engineering practice. [ABSTRACT FROM AUTHOR]

The effects of furfural generation and partitioning on the aging assessment of oil-paper insulation of power equipment were investigated. Oil-paper samples with various furfural contents were prepared using an accelerated thermal aging experiment. The mass of the furfural generated during the aging of insulation paper was calculated and used to establish the quantitative equation between the accumulated furfural and the degree of polymerization (DP) of the insulation paper. Results showed that the reciprocal of the DP value was linearly related to the amount of furfural generated by the insulation paper. Effects of temperature, moisture, and temperature on the furfural partitioning ratio between oil and paper were analyzed using a furfural partitioning experiment, and a furfural partitioning model was established. Results showed that the furfural partitioning ratio in oil was positively correlated with temperature and moisture but negatively correlated with the DP of the insulation paper. A method for assessing the age of an insulation paper by integrating the furfural generation and partitioning models was proposed and applied on a 500-kV reactor that was returned for factory maintenance. The application result indicated that the method could accurately assess the overall aging condition of the oil-paper insulation of the power equipment. [ABSTRACT FROM AUTHOR]

It is state-of-the-art to describe the dielectric behavior of an insulation material by its permittivity and its specific electric conductivity in order to estimate the dielectric stress of an insulation system. Thus, the electric field at DC voltage stress is determined according to the stationary electrical conduction field with the electric conductivity of the insulation materials. However, at oil-insulated arrangements a higher field strength in front of bare metal electrodes at high DC voltage stress occurs, which is not explainable with this model. Therefore, a charge carrier-based approach is presented to describe the dielectric behavior of the oil-paper insulation. It describes the movement of charge carriers and their effect on the electric field strength. Their drift leads to an accumulation of charge carriers in front of electrodes which results in a higher field strength in these areas, which can be calculated numerically using the Poisson-Nernst-Planck equation system. Compared to the conductivity-based model fundamental differences can be shown. Breakdown experiments qualitatively confirm the expectations according to the charge carrier-based approach. The results show that the charge carrier-based field distribution has to be considered for modelling the electrical field strength distribution at high DC voltage stress. They also show, that the dielectric behavior of these arrangements cannot be explained according to the state-of-the-art model. [ABSTRACT FROM AUTHOR]

Cooperation is a fundamental behaviour observed in all forms of life. The evolution of cooperation has been widely studied, but almost all theories focused on the cooperating individual and its genes. We suggest a different approach, taking into account the microbes carried by the interacting individuals. Accumulating evidence reveals that microbes can affect their host’s well-being and behaviour, yet hosts can evolve mechanisms to resist the manipulations of their microbes. We thus propose that coevolution of microbes with their hosts may favour microbes that induce their host to cooperate. Using computational modelling, we show that microbe-induced cooperation can evolve and be maintained in a wide range of conditions, including when facing hosts’ resistance to the microbial effect. We find that host–microbe coevolution leads the population to a rock–paper–scissors dynamics that enables maintenance of cooperation in a polymorphic state. Our results suggest a mechanism for the evolution and maintenance of cooperation that may be relevant to a wide variety of organisms, including cases that are difficult to explain by current theories. This study provides a new perspective on the coevolution of hosts and their microbiome, emphasizing the potential role of microbes in shaping their host’s behaviour. [ABSTRACT FROM AUTHOR]

A paper-based channel is a useful platform for the facile development of analytical devices implementing various chemical or biological reactions. To improve the analytical performance for various applications, it was necessary to analyze the detailed mixing characteristics within a paper-based channel. In this paper, we proposed a mathematical model to predict a concentration field created as a result of the imbibition of multiple fluids within a porous material. Interestingly, we found that the model exhibited a constant interdiffusion width within a paper-based channel even though the flow front velocity decreased over time. We were able to verify that our model accurately predicted the concentration field by comparing the experimental and numerical results for mixing in a 2 inlet-channel. Finally, we designed and fabricated paper-based channels to generate two (linear and non-linear) concentration gradients based on predictions made by the model. Both the experimental and numerical results were in good agreement, demonstrating that our model was accurate and useful for developing a paper-based analytical device utilizing the mixing characteristics of a sample and reagent flow system. [ABSTRACT FROM AUTHOR]

Dielectric response testing is a non-destructive insulation testing method that is widely used for assessing insulation properties. Time-and frequency-domain dielectric spectra are closely dependent on insulation conditions. In comparison with the time-domain spectrum, the frequency-domain dielectric response under sweep sinusoidal excitation has a stronger anti-interference capability and a more comprehensive insulation information. However, the wide application of the measurement using the frequency-domain dielectric response under sweep sinusoidal excitation is hindered by its long testing time. A possible solution is obtaining the frequency-domain spectrum by transforming the tested time-domain spectrum, such that the time- and frequency-domain spectra can be obtained in one measurement. Polarization depolarizing current measurement under DC excitation is a common time-domain testing method for time-frequency-domain conversion. However, such conversion is valid only at extremely low frequencies (less than 0.05 Hz), indicating a slight overlap with the frequency range of the measurement using the frequency-domain dielectric response under sweep sinusoidal excitation. Moreover, the effective conversion frequency range cannot be controlled manually, and the measurement using time-domain dielectric response under DC excitation is hindered by the anti-interference capability due to micro polarization-depolarization current. In addition, scholars have found nonlinearity in a partial insulation system. As the bridge of the traditional time-frequency-domain conversion, a linear extended Debye model cannot accurately reflect insulation materials that exhibit nonlinear characteristics, thereby further limiting the application scope of time-frequency-domain conversion. This study introduces the system identification theory to demonstrate the problems existing in the traditional time-frequency-domain conversion and proposes an improved time-domain testing method based on the previous work. The improved method extends the effective frequency range of time-frequency-domain conversion and emphasizes the comprehensive analysis of the insulation by combining the measured time-domain spectrum and the frequency-domain spectrum conversed from time-domain data. [ABSTRACT FROM AUTHOR]

A series of shredded paper fire experiments were conducted by means of a calorimeter. The mass loss rate and heat release rate were measured. The flame spread process was recorded, which shows that the flame spread process can be divided into four typical stages, and the mean spread rates along different directions were obtained from the observed combustion process. Based on the mean flame spread rate, a mathematical model for predicting the burning surface as a function of time during the four stages is established. Combining this model with the effective heat of combustion calculated from measured mass loss rate and heat release rate, an improved model to predict the heat release rate as a function of time was developed. In this model, the linear relationship between heat release rate and burning surface is found, and the predicted result agrees well with the measured heat release rate. [ABSTRACT FROM AUTHOR]

This paper proposes a method for estimation of tanδ of cellulosic parts in oil-paper insulation from frequency domain spectroscopy based on equivalent circuit model of oil-paper insulation in real-life transformers. Existing literature shows that overall condition of oil-paper insulation in transformer can be assessed by conventional frequency domain spectroscopy. Also, the condition of oil can be separately and easily predicted through analyzing its dielectric properties by taking out the oil samples from transformer. However, it is quite difficult to assess the dielectric properties of cellulosic parts in oil-paper insulation as it cannot be directly accessed from outside for an operating transformer. Considering the aforesaid fact, this paper presents a segregated equivalent circuit model of composite oil-paper insulation that can separately estimate the tanδ profiles for oil as well as cellulosic parts. The tanδ profiles of cellulosic parts obtained from the equivalent circuit model have been validated experimentally. Results show that the tan? profile obtained from experimental result holds good agreement with that of the proposed model. [ABSTRACT FROM PUBLISHER]

The work in this paper is applied to the Zhangbei Power grid. In the flexible direct current (DC) power system, the fault current rises extremely fast when a DC fault occurs. The requirements for the peak of breaking current and fault energy absorption of DC circuit breakers (DCCBs) increase linearly, which significantly increases the cost of the equipment. Therefore, in order to reduce the design difficulty of DCCBs, this paper proposes a strategy to control energy after the fault occurs. Firstly, the energy dimension is added on the basis of the traditional vector control of MMC, which constitutes a three-dimensional energy direct control. Subsequently, the architectures of energy fluctuation control and feedforward control are proposed. The influencing mechanisms for the peak fault current, peak fault voltage and energy dissipation are analyzed. Finally, the simulation of energy fluctuation control and feedforward control is constructed on PSCAD/EMTDC. The simulation results show that the energy fluctuation control is obviously better than the conventional three-dimensional energy control, and the feedforward energy control is further improved on this basis. Compared with the conventional vector control, the peak energy is reduced by 45.43% and the peak current is reduced by 25.39%, which helps to simplify the equipment design and reduce the equipment cost. [ABSTRACT FROM AUTHOR]

Bearings are pivotal components in mechanical systems, providing crucial support to rotating bodies. However, traditional bearings are susceptible to failure caused by friction and wear. This vulnerability is particularly pronounced in scenarios involving ultrahigh speeds and extreme conditions, necessitating the minimization of bearing losses and the enhancement of performance. Magnetic bearings, distinguished by their frictionless operation, absence of lubrication requirements, and high-speed capabilities, offer a promising solution to mitigate bearing failure attributable to friction. Nevertheless, a comprehensive review of magnetic bearings, encompassing their structural attributes, modeling mechanisms, and control strategies, is currently lacking in the literature. This paper aims to address this gap by conducting an exhaustive literature review on magnetic bearings. The objective is to provide scientists with a profound understanding of the structural characteristics, operational mechanisms, control performance, and future development trajectories of this technology. The paper begins by categorizing various magnetic bearings and conducting an in-depth analysis of their properties and characteristics, focusing on their magnetic circuit structures. Subsequently, it delves into the working principles and performance of mathematical models for magnetic bearings with different configurations, outlining the modeling procedures and optimization approaches. Additionally, the paper highlights the impact of control strategies on the performance of magnetic bearings. Modern control theory has demonstrated a remarkable 50% improvement in position accuracy and adjustment time compared to traditional PID control. Finally, the paper offers a glimpse into the future of magnetic bearing design, modeling mechanisms, and control strategies, presenting prospective directions for further advancements in this field. [ABSTRACT FROM AUTHOR]

The urban water system theory is an extension of the basin water system science on an urban scale, providing a new systematic solution for the unbalanced human-water relationship and severe water challenges, such as waterlogging, black and odorous water, and ecological degradation caused by urbanization. Most existing studies on urban water systems have focused on individual water cycle processes linked with water supply and sewage treatment plants, but mutual feedback between the water cycle and its associated material circulation and water ecology, as well as human processes, still needs further exploration. In this paper, the concept, theory, and technical methodology of the urban water system were developed based on the water cycle and basin water system science. The Urban Water System 5.0 (UWS 5.0) model was developed by integrating the Time Variant Gain rainfall-runoff Model with Urban water system (TVGM_Urban) in different underlying surface conditions for analyzing the natural-social water cycle processes and their associated water environmental and ecological processes and the influence of multiscale sponge measures. Herein, five major simulation functions were realized: rainfall-runoff-nonpoint source pollutant load, water and pollutant transportations through the drainage network system, terminal regulation and purification, socioeconomic water cycle, and water system assessment and regulation. The location for the case study used in this paper was Wuhan City. The findings showed that the entire urban water system should consider the built-up area and its associated rivers and lakes as the research object and explore the integrations among the urban natural-social water cycle and river regulations inside and outside of the city as well as the effects of socioeconomic development and sponge measures on the water quantity-quality-ecology processes. The UWS 5.0 model efficiently simulated the urban rainfall-runoff process, total nitrogen (TN) and total phosphorus (TP) concentrations in water bodies, and characteristic indicators of socioeconomic development. For the rainfall-runoff simulations, the correlation coefficient and Nash-Sutcliffe efficiency (NSE) fall under the excellent and good classes, respectively. For the TN and TP concentration simulations, results exhibited good bias and the correlation coefficients exceeded 0.90 for 78.1% of the sampled sites. The simulation of 18 socioeconomic indicators provided excellent bias, correlation coefficient, and NSE values of 100%, 83.3%, and 69.4% to total indicators, respectively. Based on the well-calibrated UWS 5.0 model, the source sponge, artificial enhancement, and source reduction-path interception-terminal treatment measures were optimized, which considerably mitigated waterlogging, black and odorous water, and lake eutrophication, respectively. The mitigation performance revealed that the maximum inundated area for a once-in-10-year rainfall event was reduced by 32.6%, the removal ratio of the black and odorous water area was 65%, the comprehensive trophic state index of water bodies was reduced by 37%, and the green development level of Wuhan City in 2020 increased from 0.56 to 0.67. This study is expected to advance the intersection and development of multidisciplinary fields (e.g., urban hydrology, environmental science, and ecology) and offer an important theoretical and technical basis for solving urban complex water issues and promoting green development of cities. [ABSTRACT FROM AUTHOR]

One of the modern, recently developed mathematical approaches for modeling various complex chaotic processes (the bacteria migration is apparently one of them), is the application of fractional differential equations. Introduction of fractional derivatives is also a very effective approach for investigation of the reactive processes (growth of bacteria in our case). Our recent advances in application of fractional differential equations for modeling the anomalous transport of reactive and non-reactive contaminants (see our recent publications in the References) allow us to expect that the anomalous transport of growing bacteria can also be effectively described by the models with fractional derivatives. Based on these modern approaches, utilizing fractional differential equations, in this paper we developed a reliable mathematical model that could be properly calibrated and, consequently, provide an adequate description of the growing bacteria transport. This model accounts for the memory effects in the bacteria transport due to the random character of bacteria trapping and release by the porous matrix. Two types of bacteria in the saturated porous medium are considered: mobile and immobile bacteria. Bacteria in the mobile phase are migrating in the fluid and have the velocity of the bulk flow, whereas bacteria in the immobile phase are the bacteria that are captured by the porous matrix. These bacteria have zero velocity and can cause clogging of some pores (therefore, porosity is possibly not constant). Examining different conventional models and comparing computations based on these models, we show that this extremely complex character of bacteria transport cannot be described by the traditional approach based on classical partial differential equations. In this paper we suggest fractional differential equations as a simple but very effective tool that can be used for constructing the proper model capable of simulating all the above-mentioned effects associated with migration of alive bacteria. Using this approach, a reliable model of the growing bacteria transport in the porous medium is developed and validated by comparison with experimental laboratory results. We proved that this novel model can be properly linearized and calibrated, so that an excellent agreement with available experimental results can be achieved. This simple model can be used in many applications, for example, as a part of more general mathematical models for predicting the outcomes of the bioremediation of contaminated soils. [ABSTRACT FROM AUTHOR]

The transient characteristics of pressure in the condenser under fault conditions have a crucial impact on the safe operation of the entire nuclear power plant. In order to ascertain whether the condenser pressure of a HPR1000 nuclear power unit meets the requirements of the steam generator, this paper establishes a mathematical model of the condenser, along with the connected steam turbine bypass steam system and circulating water system, based on Apros. The accuracy of the simulation model is verified by comparing the coasting curve of the circulating water pump with the flow change curve under the pump-tripping condition in Apros. Under the initial CCR condition and the half-side operating condition of the condenser, simulation analyses were conducted for two transient sequences involving the loss of normal external power and the simultaneous tripping of two circulating water pumps. The corresponding changes of pressure in the condenser under the transient sequence were obtained. The study reveals that, under different initial conditions and transient sequences, the condenser pressure of the unit can meet the requirements of a 12 s steam discharge to the condenser before the internal pressure of the condenser reaches the "unavailable" set value when the turbine bypass system is under the fault condition. The research findings of this paper can provide reference data for the design, commissioning, and operation of subsequent HPR1000 nuclear power plants. [ABSTRACT FROM AUTHOR]

The temperature distribution is vital to the lifetime and reliability of converter transformer bushings. However, the temperature distribution of epoxy impregnated paper converter bushings under a certain current has usually been calculated through the two dimensional model, without considering the heat convection and radiation effects. In this paper, using the computational fluid dynamics (CFD) and finite element method (FEM) analysis, a 3-D electromagnetic-fluid-thermal analysis method has been proposed. With the considering of heat conduction, heat convection and radiation, the temperature distribution of the converter transformer bushing has been simulated according to the actual operating environment. The temperature and velocity distribution of the converter transformer bushing has been obtained. Moreover, the simulation results have been compared with the experimental results to verify the accuracy of the simulation method. The simulation results, especially for the inner conductor, external conductor and the epoxy impregnated paper, are very close to the experimental results and the maximum temperature difference percentage is within 10 %, which indicates the accuracy and effectiveness of the electromagnetic-fluid-thermal analysis method proposed. [ABSTRACT FROM AUTHOR]

Dielectric response measurements in either time or frequency domain are being assessed in modern times for condition monitoring of transformer oil-paper insulation. Proper interpretation of the dielectric test results requires understanding of the physical processes taking place in the insulation structure during such tests. It is thus necessary to establish proper mathematical and analytical formulations of the insulation behavior. Dielectric response functions of various forms based on the classical ?single relaxation time? Debye model have been proposed by various researchers to model the experimental data. In complex dielectrics, it seems however, that the overall response be represented by a distribution of relaxation times (or frequencies), rather than a single ?average? response characteristic. The present contribution provides in brief, the mathematical background for estimating the dielectric response functions used so far for modeling dielectric response measurement data. Function representing distribution of relaxation frequencies has also been estimated. Experimental results on laboratory test samples and field transformers have been presented to study and understand the effects of insulation status and operating conditions on test data. [ABSTRACT FROM AUTHOR]

The Last decade saw significant growth in the digital terrestrial television (DTT) subscribers. The High peak-to-average power ratio (PAPR) of the transmitted signal is implied by the large fluctuations in its amplitude, which is a serious issue in the contemporary and next generation DTT broadcasting systems. These large fluctuations prevent feeding the high power amplifier (HPA) at an operating point near its non-linear (NL) saturation region, thereby lowering its power efficiency. For a better future, energy-efficient green communications is the need of hour. This paper focuses on digital predistortion (DPD), which is among the widely used techniques for HPA linearization in order to minimize the NL effects. DPD technique requires a feedback signal. This paper proposes a novel adding signal-based digital predistortion, where the output of the HPA is gradually linearized by adding a signal at the input in an iterative manner. By Taylor series approximation, the DPD problem can be posed as a convex one. We prove that a tighter upper bound exists for the convergence factor and instead of directly solving the convex problem, we pick a convergence factor value within its bounds that offers a good trade-off between convergence speed and residual error value. The simulation results show that the proposed technique can quickly linearize the HPA with good convergence. [ABSTRACT FROM AUTHOR]

This paper proposed a simulation method for the charge transport in single-layer oil-paper insulation. The method of transient upstream finite-element method (FEM) is derived in order to calculate the time variation of charge densities in medium. The numerical simulation of charge transport in the single-layer oil-paper insulation is realized by applying the transient upstream FEM to the transport equations of bipolar charges. With reasonable microparameter, the charge transport in an experimental object is simulated. The simulation results are consistent with the experimental data. A bent model of oil-paper insulation is analyzed to study the charge distribution under the actual condition. This paper provides an exploratory research to the simulation of charge phenomenon in oil-paper, and has guiding significance to the design of oil-paper insulation. [ABSTRACT FROM AUTHOR]

In order to study the paper-making machine as the control object, a simplified structure scheme was drawn up. The paper-making machine was analysed as the object of optimal control. In order to maximise productivity the selection of periods number of fovming machine was instified. The assifned task of optimal control was solved and practical results were obtained. [ABSTRACT FROM AUTHOR]

The paper presents new diagnostic method applied to assess aging degree for paper-oil insulation used in professional electrical power device, primarily including medium and high power transformers. The described method is based on modified diagnostics using the recovery voltage effect occurring in dielectrics (RVM ? Recovery Voltage Methods). Modification of the RVM method applied so far, which is now used only to assess moistening degree for paper-oil insulation in power transformers, consists in a new parametric analysis of recovery voltage time characteristics. Simulation and experimental tests carried out in laboratory conditions for adequately prepared insulation samples have proven that the time-constant of recovery voltage decay (?R_MIN) is the most susceptible parameter as regards quantitative change in the function of aging of the examined insulation. This conclusion is also confirmed by statistical studies, in which a multi-parameter variance analysis method has been applied. An original equivalent circuit diagram of the insulation has been used to simulate aging degree of paper-oil insulation samples in numerical tests. The diagram is based on the Cole-Cole type dielectric response model. [ABSTRACT FROM AUTHOR]

This work investigates the effect of alternating current partial discharge (AC PD) byproducts on the dielectric frequency response (DFR) of oil-paper insulation comprising of a small cavity, in the frequency range of 1.0 mHz to 1.0 kHz. The investigations were done by utilizing experimental results in combination with a Finite Element Method (FEM) model. The results presented in this paper show that ageing by-products in the cavity (PD stressed volume) alone will not result into the change in DFR of oil-paper insulation. According to simulation results, the significant change in the DFR results is mainly caused by PD by-products (positive and negative charges, and electrons) which tend to conduct or diffuse into the bulk of oil-paper insulation. The change in a dissipation factor curve due to PD by-products was observed to occur mainly in the middle and low frequency regions. The results indicate that the dissipation factor curves in the middle and low frequency regions depend on the level of PD by-products in oil and paper, respectively. [ABSTRACT FROM AUTHOR]

The service life of a transformer is determined by the condition of its oil?paper insulation. A modified Cole?Cole model was introduced to describe the frequency domain spectroscopy (FDS) curves based on the classic Debye relaxation model and thereby accurately determined the ageing state of the insulation of a power transformer using FDS. Oil?paper insulation samples with different ageing states are prepared under laboratory conditions, and a characteristic parameter is extracted to quantify their ageing states after a detailed investigation of the frequency domain dielectric properties of the samples. Results reveal that the modified Cole?Cole model, including the ? relaxation components, dc and hopping conductivity components, can be employed to effectively model the frequency dielectric characteristics of oil?paper insulation. Furthermore, the extracted characteristic parameter from this model, ??, can be utilized in the quantitative evaluation of the ageing states of transformer insulation. A case example is discussed to demonstrate the applicability of the proposed technique in the condition assessment of field power transformers. [ABSTRACT FROM AUTHOR]

The paper uses regression analysis to research the movement dynamics of charge materials along the paths of a blast furnace coneless loader device. The research's main goal is to consider two main factors when optimizing the loading process of the blast furnace - the opening degree of the charge shutter of the loading device hopper and the inclination angle of the distribution tray. That approach allows the optimization of the loading impact, taking into account the current change in the granulometric parameters of the blast furnace charge. A model for determining the dynamic parameters of the charge flow in the case of its movement along the paths of the blast furnace coneless loading device has been developed. [ABSTRACT FROM AUTHOR]

Ca 2 + is a ubiquitous signaling mechanism across different cell types. In T-cells, it is associated with cytokine production and immune function. Benson et al. have shown the coexistence of competing Ca 2 + oscillations during antigen stimulation of T-cell receptors, depending on the presence of extracellular Ca 2 + influx through the Ca 2 + release-activated Ca 2 + channel (Benson in J Biol Chem 29:105310, 2023). In this paper, we construct a mathematical model consisting of five ordinary differential equations and analyze the relationship between the competing oscillatory mechanisms.. We perform bifurcation analysis on two versions of our model, corresponding to the two oscillatory types, to find the defining characteristics of these two families. [ABSTRACT FROM AUTHOR]

Celyvir is an advanced therapy medicine, consisting of mesenchymal stem cells (MSCs) containing the oncolytic virus ICOVIR 5. This paper sets out a dynamic system which attempts to capture the fundamental relationships between cancer, the immune system and adenoviruses. Two forms of treatment were studied: continuous and periodic, the second being closer to the real situation. In the analysis of the first model, in addition to identifying the critical points, their properties and bifurcation points, a number of numerical simulations were carried out. It has thus been shown that there are bistability regimes in which Celyvir can produce an equilibrium of tumor progression, or even freedom from tumor. A sensitivity analysis was also performed to determine which parameters are most important in the system. Subsequently, an optimal control problem with nonlinear objective functional has been formulated, where the therapeutic goal is not only to minimize the size of the tumor cell population and the total cost of treatment, but also to prevent the tumor from reaching a critical size. It has been shown that the optimal control is bang–bang. With the second model, a threshold value of viral load has been identified at which the success of the treatment could be ensured. It is clear in both models that a low viral load would lead to relapse of the disease. Finally, it is shown that a periodic bang–bang regime should be used to optimize treatment with Celyvir. [ABSTRACT FROM AUTHOR]

Reasonable workshop layout can reduce the transportation distance, reduce the production cost and improve the production efficiency. Aiming at the problem of unreasonable workshop layout, this paper takes an actual case as the research object and studies its workshop layout. Firstly, the mathematical model with the objectives of minimizing logistics transportation cost and maximizing non-logistics relationship is established. Then, the sparrow search algorithm (SSA) is used to find the optimal layout that satisfies the objective function. Finally, Flexsim software is used to simulate the layout scheme. The results show that compared with the genetic algorithm and the original layout scheme, the layout scheme obtained by the SSA algorithm reduces the total transportation distance by 26 m and 325 m, and improves the non-logistic relationship by 1.6% and 24.84%, respectively. Optimizing the layout using SSA algorithms increases product productivity, which is a good improvement over the original workshop layout. [ABSTRACT FROM AUTHOR]

Rabies is one of the oldest viral diseases and it has been present on every continent except Antarctica. Within the U.S. human rabies cases are quite rare. In the eastern USA, raccoons are the main reservoir hosts and pet vaccination serves as an important barrier against human rabies exposure. In this paper, we develop a compartmental model for rabies transmission amongst raccoons and domestic pets. We find the disease-free equilibria, reproduction numbers for the raccoons and domestic pets. We also determine the vaccination coverage/rates, both for raccoons and pets, needed to achieve the elimination of rabies. [ABSTRACT FROM AUTHOR]

Preventive treatment for people with latent Tuberculosis infection (LTBI) has aroused our great interest. In this paper, we propose and analyze a novel mathematical model of TB considering preventive treatment with media impact. The basic reproduction number R0 is defined by the next generation matrix method. In the case without media impact, we prove that the disease-free equilibrium is globally asymptotically stable (unstable) if R0 <1 (R0 >1). Furthermore, we obtain that a unique endemic equilibrium exists when R0 > 1, which is globally asymptotically stable in the case of permanent immunity and no media impact. We fit the model to the newly reported TB cases data from 2009 to 2019 of four regions in China and estimate the parameters. And we estimated R0 = 0:5013 < 1 in Hubei indicating that TB in Hubei will be eliminated in the future. However, the estimated R0 = 1:015> 1 in Henan, R0 = 1:282 >1 in Jiangxi and R0 = 1:930 >1 in Xinjiang imply that TB will continue to persist in these three regions without further prevention and control measures. Besides, sensitivity analysis is carried out to illustrate the role of model parameters for TB control. Our finding reveals that appropriately improving the rate of timely treatment for actively infected people and increasing the rate of individuals with LTBI seeking preventive treatment could achieve the goal of TB elimination. In addition, another interesting finding shows that media impact can only reduce the number of active infections to a limited extent, but cannot change the prevalence of TB. [ABSTRACT FROM AUTHOR]

• A modified evaporative condenser model with 4 characteristic parameters is proposed. • Data screening and supplementation methods are developed for on-site applications. • The average relative errors of the training and test sets are 2.10 % and 2.87 %. • Air–water mass transfer is the major factor in enhancing thermodynamic performance. Evaporative condensers (ECs) have been widely adopted in the fields of refrigeration, petrochemicals, etc. owing to the advantages of low water and energy consumption. However, due to the lack of a reliable mathematical model, the energy-saving potential of ECs remains unexplored. To realize thermodynamic performance predictions under on-site conditions, a generic model with 4 characteristic parameters, that could be identified specifically for different ECs, is innovatively proposed in this paper. Taking the refrigeration system of a food factory as a case study, a well-organized data processing method including filtering, screening, and supplementation is established. The processed real-operating data is used for characteristic parameters identification and model validation. Simulations indicate satisfactory transferability and a good agreement between the test and simulated results, with average relative errors of 2.10 % and 2.87 % for the training and test sets, respectively. Based on the proposed model, the overall performance and the working fluids' thermodynamic state of the EC during operation are investigated carefully. It could be concluded that the air–water mass transfer is the dominating factor in enhancing EC's thermodynamic performance, and air flow shows greater significance than water in improving heat exchange capacity. The heat exchange intensity of the superheating and two-phase zones is similar, while that of the subcooling zone is the lowest, averaging only 37.9 %. [ABSTRACT FROM AUTHOR]

A fast numerical algorithm for solving the Cauchy problem for elliptic equations with variable coefficients in standard calculation domains (rectangles, circles, or rings) is proposed. The algorithm is designed to calculate the heat flux at the inaccessible boundary. It is based on the separation of variables method. This approach employs a finite difference approximation and allows obtaining a solution to a discrete problem in arithmetic operations of the order of N ⁢ ln ⁡ N , where 푁 is the number of grid points. As a rule, iterative procedures are needed to solve the Cauchy problem for elliptic equations. The currently available direct algorithms for solving the Cauchy problem have been developed only for (Laplace, Helmholtz) operators with constant coefficients and for use of analytical solutions for problems with such operators. A novel feature of the results of the present paper is that the direct algorithm can be used for an elliptic operator with variable coefficients (of a special form). It is important that in this case no analytical solution to the problem can be obtained. The algorithm significantly increases the range of problems that can be solved. It can be used to create devices for determining in real time heat fluxes on the parts of inhomogeneous constructions that cannot be measured. For example, to determine the heat flux on the inner radius of a pipe made of different materials. [ABSTRACT FROM AUTHOR]

Studying Arctic ice formation stays in the focus of research groups over the past decades in the context of ice cover changes, thermal budget and climate agenda in general. Nevertheless, the phenomenon's underlying mechanisms are still not completely understood and described. The main reason for the lack in understanding is the limited experimental access to the field data when it comes to the processes that occur below the ice floe. Thus, there is a need to build competent analogies between the natural (ocean water–ice) and laboratory (here: binary alloy) conditions of the experiment as a step of data preparation for the verification of the mathematical model. In the current paper, the existing qualitative models describing the process of melting and crystallization were expanded and the experimental method was developed copying the layering of the natural ocean water–ice mixture. The experimental set‐up for studying the solidification within the intermediate zone was designed for Al–Cu alloys being the system with appropriate solidus line for creating a sufficient concentration gradient and by that temperature dependent phase fraction under isothermal conditions. The gained experimental data were used for validating a binary phase‐field model for solidification considering moving boundaries. The model includes the description of the free energy of both phases and their respective diffusion coefficients. It allows modeling a binary system at a mesoscopic spatial level by including the concentration‐driven phase transition and resolidification in the two‐phase region. The novel results will help the quantitative understanding of solidification phenomena and are highly‐evaluated from interdisciplinary point of view, including glaciology and geosciences, being ultimately significant for the understanding the global climate change landscape. [ABSTRACT FROM AUTHOR]

The aim of this paper is to examine the stability of a class of nonlinear stochastic operators on a finite‐dimensional simplex. We identify a number of properties of the set of the class of stochastic operators, including the stability of each operator. We then use these operators to define non‐homogeneous Markov measures that rely on initial data and carry out an investigation into the absolute continuity and singularity of these measures. [ABSTRACT FROM AUTHOR]

The corrosion problem of the tank floor of the oil depot tank area becomes more and more serious with the extension of the operation time. At present, how to determine the potential distribution of the storage tank floor and how to judge the cathodic protection effect of the storage tank floor is the bottleneck of technological development. In this paper, by constructing a mathematical model of cathodic protection in the tank area, influence of deep well anode on potential distribution of tank bottom is calculated by boundary element method (BEM) with computer programming, to study the potential distribution of the tank floor under different anode parameters. The results show that the calculated results are in good agreement with the field measured results, which verifies the accuracy and reliability of the calculation. [ABSTRACT FROM AUTHOR]

Gumboro disease is a viral poultry disease that causes immune suppression on the infected birds leading to poor production, mortality, and exposure to secondary infections, hence a major threat in the poultry industry worldwide. A mathematical model of the transmission dynamics of Gumboro disease is developed in this paper having four compartments of chicken population and one compartment of Gumboro pathogen population. The basic reproduction number R og is derived, and the dynamical behaviors of both the disease-free equilibrium (DFE) and endemic equilibrium are analyzed using the ordinary differential equation theory. From the analysis, we found that the system exhibits an asymptotic stable DFE whenever R og < 1 and an asymptotic stable EE whenever R og > 1. The numerical simulation to verify the theoretical results was carried out using MATLAB ode45 solver, and the results were found to be consistent with the theoretical findings. [ABSTRACT FROM AUTHOR]

In this paper, we consider a mathematical model "politics-economy" described by a nonlinear system of differential equations with a parameter and obtain conditions for the existence of a nonzero positive periodic solution. [ABSTRACT FROM AUTHOR]

In this paper, we use a previously developed measles model to forecast measles in Turkey for the period 1970–2021. We study the structural identifiability of the model both by hand and using software. By hand, we assume the prevalence and the total population size are given. Using software, we assume the incidence and the total population size are given. The model is structurally identifiable if one of the three parameters is fixed. We notice that Turkey has a significant change in time of the immigration rate and vaccination proportions, so we assume these two quantities are time-dependent. We fit the nonautonomous model to the measles incidences in Turkey for 1970–2021. We perform practical identifiability of the fitted model, and find that all parameters but one are practically identifiable. When fixing the unidentifiable parameter to a value derived from additional data, we obtain that all parameters are practically identifiable. [ABSTRACT FROM AUTHOR]

In this paper the accelerated aging experiments of oil-paper insulation are carried out to simulate the oil-paper aging process under normal thermal aging process. On the basis of the results of accelerated aging experiments, how the deviation degree of aging status change under the same aging factors is studied, and a method to calculate the failure probability due to the loss of mechanical strength of the insulation is put forward. This paper presents an approach for economic assessment on insulation diagnosis through accelerated aging experiments. The foundation of this approach for economic assessment on insulation diagnosis is to establish condition simulation method of triple relationships between condition status, aging time and failure probability according to data from accelerated aging experiments. The conclusions are made that the economic and technical factors can affect the optimum life cycle cost of each maintenance strategy, which consequently affects the economic feasibility of condition-based maintenance strategies. [ABSTRACT FROM AUTHOR]

Conditions for the existence and uniqueness of mild solutions for a system of semilinear impulsive differential equations with infinite fractional Brownian movements and the Wiener process are established. Our approach is based on a novel application of Burton and Kirk's fixed point theorem in extended Banach spaces. This paper aims to extend current results to a differential-inclusions scenario. The motivation of this paper for impulsive neutral differential equations is to investigate the existence of solutions for impulsive neutral differential equations with fractional Brownian motion and a Wiener process (topics that have not been considered and are the main focus of this paper). [ABSTRACT FROM AUTHOR]

To study the viscosity coefficient and thickness of the viscous layer on the Tibetan Plateau, the relationship between the change in viscosity coefficient and thickness of a lower crustal flow and the change in elevation has been investigated based on the principle of a pipeline flow with different viscosity and thickness of terrain elevation. The viscosity and thickness of the lower crustal flow in different directions were determined based on the changes in the terrain along different directions on the Tibetan Plateau. The following results were obtained: (1) The greater the viscosity and the smaller the thickness of the lower crustal conduit flow, the steeper the ground elevation change formed; (2) The maximum viscosity coefficient in the region from India to the Kunlun Mountains in the southern Tibetan Plateau through the Himalayan boundary is approximately 1020Pas, and the thickness of the conduit flow is approximately 25 km. (3) The maximum value of the viscosity coefficient of the lower crustal flow in the region ranging from the Tibetan Plateau to the Qinghai- Gansu section is attained when the flow thickness in this region approaches 40 km (4) The maximum value of the viscosity coefficient of the lower crustal flow in the region ranging from the Tibetan Plateau to the Qinghai- Gansu section is attained when the flow thickness in this region approaches 40 km., which does not substantially differ from that of the region ranging from the Tibetan Plateau to the Qinghai-Gansu area. (5) The maximum viscosity coefficient of the lower crustal flow from the southeast of the Tibetan Plateau to Yunnan is approximately 1018Pas, and the thickness is approximately 32 km, which differs from the flow thickness in the Sichuan Basin and Qinghai-Gansu regions. The results show variations in the viscosity of the flow along different directions on the Tibetan Plateau, in addition to considerable variation in the thickness of the lower crustal channel flow from region to region, with the overall characteristics of thinness in the west and thickness in the east. The results of the four profiles reveal that the channel flow thickness is the steepest at the southwest border of the Tibetan Plateau with India. This paper presents a reasonable interpretation of the geomorphology of the Tibetan Plateau using different thickness and viscosity coefficients of the lower crustal channel flow model. In this paper, a possible mechanism for the formation of the Tibetan Plateau topography is explained using a horizontal pipe flow for four profiles of the Tibetan Plateau. [ABSTRACT FROM AUTHOR]

The optimal construction of long-span ziplines represents a complex engineering and construction task, especially from a safety point of view. In contemporary literature and engineering practice, there are no appropriate theoretical bases, standards and recommendations directly related to this issue. The aim of this work is to try to define the appropriate theoretical and professional basis for the design of these devices. The paper describes the procedure for creating a mathematical model of a zipline, followed by experimental verification of the formed mathematical model on a particular zipline, and afterwards by an analysis of the influencing parameters. The beginning of the paper defines the theoretical background that is necessary for the mathematical model forming of descending a rider down a heavy rope that takes into account mechanical and aerodynamical resistances that occur during the descent, after which a description of formation of the model itself is given. The next part of the paper gives a detailed description of the zipline on which the measurements were made, and a complete description of the used measuring equipment. Then succeeding part contains measurement results, followed by verification of the mathematical model by comparing the measured and calculated values. In the end, the influence of relevant parameters are analyzed by using the mathematical model and adequate conclusions are drawn. [ABSTRACT FROM AUTHOR]

Final dewatering in the production of dry creped tissue is performed by Yankee drying, which includes hot pressing followed by simultaneous contact and impingement drying. The present study models Yankee drying and compares simulation results to the data obtained from trials on a pilot tissue machine. It advances models published previously by the representations developed for the transport of heat in the pressing stage and for the heat transfer involved in the dehydration of the cylinder coating spray. The model predicts an average specific drying rate within 4% in the range of the experimental data used. [ABSTRACT FROM PUBLISHER]

The numerical method for modeling the behavior of nanofluid within the closed container in the presence of Lorentz force was dissected in this paper. The working fluid contains water and two shapes of nanoparticles. The porous geometry has one sinusoidal inner surface which faces constant heat flux. Influences of gravity and vertical Lorentz was complicated in modeling and momentum equations have been edited with adding related source terms. The precision of code was tested and respectable agreement has been obtained. The influences of loading nanomaterial and strength of two important forces (gravity and buoyancy) have been analyzed in the result section. Loading nanoparticles leads to a growth of Nu around 26.99% and 41.04% when Ha = 0 and 15. Increasing buoyancy leads to augment of Nu about 44.34% and 1.46% in the absence and existence of Ha. Applying Lorentz force makes Nu to decrease about 40.39% when Ra = 7 0 0. [ABSTRACT FROM AUTHOR]

This paper is concerned with the deduction of a mathematical model for the small longitudinal vibrations of a bar where one end is clamped and in the other end is glued a concentrated mass. The existence of global solutions of this model perturbed with a general nonlinear internal dissipation and with a general nonlinear boundary dissipation is derived. For a particular case, the exponential decay rate of the energy is obtained. [ABSTRACT FROM AUTHOR]

The principal economic sector devoted to the breeding, raising, and production of farm animals is known as the livestock industry. There are precise standards for making high-quality feed in animal husbandry. Precision livestock feeding is a crucial component, with the potential to significantly impact the profitability of livestock; it permits the provision of diets to animals that are precisely tailored to their specific daily nutritional needs. Through simulation modeling, a single model can be created for automated systems to determine daily rations for farm animals. For the purposes of this document, precision livestock feeding refers to the practice of tailoring feed to individual animals or groups of animals, taking into account their changing nutritional needs over time and individual differences in terms of nutritional requirements. The practice aims to optimize animal health and performance while reducing feed waste. This paper presents a formal model for determining the quantities of components needed to achieve a minimum cost mixture that satisfies compositional and quantitative criteria. The present research calculates the amount of hay and silage required to feed an animal per day at the most economical cost by applying an optimization approach that involves defining and solving an optimization problem. The problem is solved using a well-known software package, which is necessary for the practical application of the resulting model. Real data from livestock production in Bulgaria are used to numerically test the model. [ABSTRACT FROM AUTHOR]

In this paper, six-band double negative (DNG) metamaterial with a substantially high effective medium ratio (EMR) under the S and C microwave band is designed and investigated for multiple microwave applications. The proposed metamaterial unit cell consists of four Plus Appended Split Ring Resonator (PASRR) cells, which are combined with variable sides and positions by plus (+) shape stubs at the centre. All four Plus Appended Split Ring Resonator (PASRR) cells are mutually coupled with each other to vary the electrical length to achieve hexa Bands DNG characteristics in a lossy FR-4 epoxy substrate with the thickness of 1.5748 mm. A parameter extraction method has been used to extract effective permittivity (εeff), permeability (μeff) and refractive index (n). Moreover, the equivalent circuit model is obtained. Ansys HFSSTM software & Keysight ADSTM software are used to obtain the simulated and theoretical results, respectively, which agree measured with simulated and theoretical results. [ABSTRACT FROM AUTHOR]

Parabolic trough collectors (PTCs) have came out as a promising technology for harnessing solar energy for various applications including electricity generation and thermal heating. However, improving their thermal performance remains a critical challenge to maximize energy conversion efficiency. This paper presents a mathematical model for enhancing the thermal performance of PTCs by using a curved Fresnel lens as a second collector over the top side of the receiver. This enhancing has taken advantage of the space above the top side of receiver and increased the thermal efficiency of PTCs. The unsteady heat transfer equations with one dimension are used to simulate the effect of Fresnel lens on the receiver components beside the heat transfer fluid and compared with that without Fresnel lens. The results of this model are based on parameters of LS-2 model and environment of installation place whereas the water was chosen as heat transfer fluid with physical properties depending on Temperature. Albaydha city in Yemen is chosen as an installation place taking in consideration the variation of environment temperature in each month of the year and the inlet temperature of water and receiver's components are taken as the minimum temperature of the air. [ABSTRACT FROM AUTHOR]

This paper studies a nonlinear fractional mathematical model for hand, foot, and mouth Disease (HFMD), incorporating a vaccinated compartment. Our initial focus involves establishing the non-negativity and boundedness of the fractional order dynamical model. The existence and uniqueness of the system are discussed using the Caputo derivative operator formulation. Applying a fixed-point approach, we obtain results that confirm the presence of at least one solution. We analyze the stability behavior at the two equilibrium points (disease-free and endemic states) of the model and derive the basic reproduction number. Numerical simulations are conducted using the fractional Euler approach, and the simulation results confirm our analytical conclusions. This comprehensive approach enhances the understanding of HFMD dynamics and facilitates the policy making of health care centers to control the further spread of this disease. [ABSTRACT FROM AUTHOR]

Back pain is regularly associated with biomechanical changes in the spine. The traditional methods to assess spine biomechanics use ionising radiation. Vertebral Metrics (VM) is a non-invasive instrument developed by the authors in previous research that assesses the spinous processes' position. However, the spine model used by VM is not accurate. To overcome it, the present paper proposes a pioneering and simple articulated model of the spine built through the data collected by VM. The model is based on the spring–mass system and uses the Levenberg–Marquardt algorithm to find the arrangement of vertebral bodies. It represents the spine as rigid geometric transformations from one vertebra to the other when the extremity vertebrae are stationary. The validation process used the Bland–Altman method to compare the Cobb and the intervertebral angles computed by the model with the radiographic exams of eight patients diagnosed with Ankylosing Spondylitis. The results suggest that the model is valid; however, previous clinical information would improve outcomes by customising the lower and upper vertebrae positions, since the study revealed that the C6 rotation slightly influences the computed angles. Applying VM with the new model could make a difference in preventing, monitoring, and early diagnosing spinal disorders. [ABSTRACT FROM AUTHOR]