Method For Calculation Of Parameters Research Articles

An equivalent modeling method of passive components with multi‐resonant frequency

SummaryHigh‐frequency characteristics of passive components are crucial to the electromagnetic compatibility (EMC) of an electronic system, and modeling of passive components is of significance for EMC analysis. However, challenges remain in the modeling of passive components with multiple resonant frequencies. In this paper, a method for establishing equivalent models of multi‐resonant frequency passive components, including capacitors, inductors, and resistors, is proposed. Firstly, high‐frequency equivalent circuit topologies of the multi‐resonant frequency passive components, which are simple, easy to understand, and can be applied to the modeling of passive components with various impedance characteristics, are developed. Secondly, a calculation method of equivalent circuit parameters based on least squares and particle swarm optimization (PSO) is presented, which is not sensitive to the initial value, only needs the estimated range of the equivalent circuit parameters, and very suitable for getting the parameters of equivalent circuit models accurately and efficiently. Finally, to validate the method, some SPICE models of single components are established, and a PCB‐level EMC analysis is implemented. The comparisons of the simulated and experimental results show the validity and accuracy of the method. The method is very useful for future components modeling when doing EMC design or other high‐frequency designs.

On-Line Monitoring of Shunt Capacitor Bank Based on Relay Protection Device

In modern power systems, the installation of a shunt capacitor bank is one of the cheapest and most widely used methods for improving the voltage profile. One shunt capacitor bank is composed of mass capacitor units and have ground, ungrounded, delta, wye connections that make configuration of capacitor banks is various. In the case of long-term operation, the failure of a single capacitor unit of a capacitor bank is likely to cause uneven voltage, which will lead to the breakdown and burning of the whole group, resulting in huge losses. The relay protection device can detect the simultaneous voltage and current of the capacitor. By utilizing these data from the relay, the abnormal state of the shunt capacitor banks at the initial stage of the fault can be found through monitoring the slight change in capacitance. Timely and early maintenance and repair would avoid capacitor bank faults and potentially greater economic losses. Capacitor banks have different connection modes. For ungrounded wye-connected capacitor banks with an unknown neutral point voltage, the capacitance parameters of each branch cannot be calculated. A parameter symmetry based on the calculation method for capacitor parameters is proposed. For long-term monitoring and observation of the capacitor capacitance value, the fault state and abnormal state of the capacitor are identified based on statistical methods. The simulation established by PSCAD verified that a relay protection device can realized an effective monitoring of the early abnormal state of the capacitor bank.

Analysis of Cross-Bonded Cables Using Accurate Model Parameters

This paper presents a thorough investigation of frequency and electromagnetic transient (EMT) responses of cross-bonded cables. The study adopts newly developed Line/ Cable Data (LCD) Module in an existing EMT-type simulation software. The input impedances evaluated by positive sequence and various mode energizations on a typical cross-bonded cable (CBC) in frequency domain are investigated.In addition to cross-bonded, the solid-bonded cable (SBC) and core-transposed cable (CTC) are analyzed for characteristics of input impedance. The mixed propagation modes of CBC and CTC are studied. The influence of bonding methods and cable models on transient voltages is investigated. The results simulated by the new LCD are compared with the Classical Parameter Calculation (CPC) method and validated by recently proposed extended transmission line (ETL) approach.

Investigation on temperature control based on cooled mine compressed air for mine refuge chamber with high-temperature surrounding rock

Acceptable temperature is very important for mine refuge chamber (MRC) to ensure the safety of occupants. A novel temperature control scheme combining cold source storage with mine compressed air (MCA) was proposed for MRCs. An experiment was conducted to explore the characteristics of temperature controlling in a MRC via the MCA. Effects of several main factors such as initial surrounding rock temperature (ISRT), ventilation temperature (VT), ventilation rate (VR) and heat rate (HR) on the performance of temperature controlling in the MRC were numerically studied. Results show that: (1) In the MRC, the heat transfer process between the air and walls will reach a dynamic equilibrium within 0.5 h; (2) The ambient temperature in the MRC increases linearly with the square root of time from 1 h to 96 h, the gradient increases with VT and HR but decreases with ISRT and VR; (3) Ventilation with rate of 0.3 m3/min per capita and temperature of 20 °C can meet the temperature control requirements of a MRC located in the sandstone layer with the ISRT of 32.2 °C. An empirical formula for predicting ambient temperature and a ventilation parameter calculation method for meeting the temperature control goal of the MRC are obtained.

Calculation of Main Circuit Steady-State Parameters for Capacitor Commutated Converter System

The calculation of the main circuit parameters is the basic part of the engineering design for high voltage direct current (HVDC) transmission systems. Compared to the conventional line commutated converter (LCC), the application of the capacitor commutated converter (CCC) can reduce the probability of commutation failures and the shunt capacitor reactive compensation. This paper proposes a calculation method of main circuit parameters for the CCC-based HVDC system. Firstly, the topology of a CCC-HVDC transmission system is described. Secondly, based on the steady-state mathematical model of the CCC, the paper proposes the calculation method of the commutation capacitor to satisfy the system requirements, and the calculation formulas of the main circuit parameters are also given. Then the calculation procedure of the main circuit steady-state parameters is described in detail considering system parameters, control modes, calculation tolerances and operating conditions. Finally, a two-terminal ±500 kV/3000 MW LCC-CCC HVDC transmission system is presented to verify the validity of the main circuit parameter calculation method. The proposed method has great significance for the AC filter design in practical engineering application.

Air quality monitoring of sow houses with the fuzzy comprehensive evaluation method

AbstractThe comfort of sow house environments is dependent on several aspects. Therefore, it is difficult to accurately assess and control the environment by applying a single factor. In this study, Shannon's entropy theory, the fuzzy comprehensive evaluation (FCE) method, as well as the improved analytic hierarchy process (IAHP) were combined to provide reasonable subjective and objective weights for environmental comfort evaluation modeling. In addition, an evaluation index system including five environmental factors was established. To decide the membership degree of each environmental factor, we proposed a method to establish fuzzy membership functions (MFs) and devised a calculation method for related parameters. Three basic types of MFs, including the trapezoidal membership function (trapmf), pi‐shaped membership function (pimf), and ridge membership function (ridgemf), were adopted to establish an evaluation model that fit well with the entropy‐IAHP‐FCE model. The proposed method was verified using real measurements of spatiotemporal data, and results show that multiple environmental parameters were successfully integrated into the FCE for sow house environment evaluation. The FCE method delivered higher correlation coefficients of 0.8785, 0.9512, and 0.9719 compared with the temperature‐humidity index, single‐factor evaluation, and least squares support vector regression methods. The FCE method enhances sensitivity and performs an effective evaluation of environmental comfort. It can be integrated into environmental control and early‐warning systems for environmental management optimization, thereby enhancing sow production and welfare.

Nonlinear Transient Mathematical Model of Large-Capacity Synchronous Condenser Based on Time-Varying Reactance Parameters

Large-capacity synchronous condenser (SC) is an essential dynamic reactive power compensation device in an Ultra-high voltage direct current (UHVDC) transmission system. The particular transient operating state and structural characteristic of SC lead to a severe magnetic saturation effect during transient operation. To accurately describe the dynamic characteristics of SC, it is urgent to establish a transient mathematical model considering the magnetic saturation effect. Therefore, this paper proposes a nonlinear transient mathematical model for SC based on time-varying reactance parameters and gives a calculation method for time-varying reactance parameters. The mathematical model proposed in this paper is verified by taking a 300MVar SC as the research object. This condenser is connected to the power grid at the sending end of the UHVDC transmission system. The proposed mathematical model, the traditional fixed-parameter transient mathematical model, and the saturated standard SG model used in the power system were used to simulate the voltage generated by dynamic reactive power compensation characteristics of SC during a drop failure. Compared with the fault test results, the accuracy of the proposed mathematical model is verified. The effect of magnetic saturation on the dynamic reactive power compensation characteristics was analyzed, respectively. In addition, the accuracy of the proposed mathematical model is closer to the actual motor state, which is helpful for further research on the operation analysis and state monitoring of SC.

A dataset of UAV multispectral images for the grassland-livestock balance

The grassland-livestock balance system plays an important role in reconciling the protection of grassland resources with the sustainable development of animal husbandry. The accurate estimation of the grassland-livestock balance is the basis for the implementation of the grassland-livestock balance system. In order to explore the accurate calculation method of the important parameter, i.e. livestock grass demand in the calculation system, in this study, we set up an experimental area in the natural grassland of Hulunbuir, Inner Mongolia, to simulate a real grazing scene, and conducted 4 grazing experiments controlling the sheep number and grazing time. We obtained multispectral images of the experimental area before and after grazing were with the help of the UAV remote sensing, and carried out a quadrat survey. After data sorting and preprocessing, we produced this dataset of high spatial resolution image data and accurate quadrat investigation data. It can be applied to the research on the daily grass demand of grazing sheep on Hulunbuir meadow steppe in autumn. This dataset provides data support for the accurate estimation of local grassland-livestock balance, and is of great significance for the adaptive dynamic management of grass and livestock.

Analysis of uncertainty propagation path of fire-induced domino effect based on an approach of layered fuzzy Petri nets

In the chemical industry parks, large amounts of hazardous substances are processed and stored, while the leakage of hazardous substances can easily trigger a domino effect. Probit models were widely used to assess the escalation probability of domino effects, but ignoring the synergistic effects in higher-order propagation. In this paper, based on expert knowledge to identify the propagation rules of domino effects, a layered fuzzy Petri net (LFPN) is proposed to model the multi-order domino effect propagation paths. In the process of fuzzy reasoning, the calculation method of LFPN relevant parameters is provided. Finally, a case study demonstrates the validity of the proposed method for fire-induced domino effects, while the research content contributes to an in-depth understanding of the characteristics of domino effects and provides a theoretical basis for blocking the evolutionary process of domino effects.

Space projectile explosion position calculation method based on curved multi‐lens array sensor

AbstractIn the weapon test range, the space projectile explosion position parameter at the terminal trajectory is an important index to evaluate the damage performance of the projectile fuze. Due to the random distribution of the falling dispersion of the projectile, it is difficult to test the projectile explosion position in the long‐range terminal trajectory falling area. To solve this problem, this paper proposes a method for measuring the projectile explosion position based on ultra‐wide imaging with a multi‐lens array. A curved multi‐lens array optical imaging system is designed and the parameter calculation method of the optical system is presented. The relationship between the space projectile explosion position and the center of the sub‐eye lens and the relationship between the center of the sub‐eye lens and the imaging point of the image sensor is established according to the imaging principle of the optical system. The object image relations of any seven adjacent sub‐eye lenses of the curved multi‐lens array optical imaging system are combined and the calculation model of the space projectile explosion position is deduced. The experimental results verify that the designed curved multi‐lens array optical imaging system and the calculation model of the projectile explosion position proposed in this paper are reasonable.

An improved Carnegie-Ames-Stanford Approach model for estimating ecological carbon sequestration in mountain vegetation

The vegetation in mountainous areas is abundant, and its ecological carbon sequestration ability is of great significance to maintain the sustainable and healthy development of the ecological environment. However, when estimating the carbon sequestration of mountain vegetation, the Carnegie-Ames-Stanford Approach (CASA) model assigns a uniform value to the maximum light energy utilization (εmax = 0.389 gC/MJ), ignoring the influence of vegetation types and topographic factors on εmax, resulting in the low accuracy of the CASA model in estimating the carbon sequestration of mountain vegetation. In this paper, the improved CASA model was combined with Landsat 8 Operational Land Imager (OLI) remote sensing image data to improve the estimation accuracy of carbon sequestration of mountain vegetation. The first was the establishment of a linear link between the terrain characteristics (slope and aspect), vegetation types, and εmax in mountainous locations. The second was the improvement of the CASA model’s calculation method for key parameters. The different distributions of the estimation results from the two techniques in 2015 and 2016 are then compared using Landsat 8 data as the data source, and the impact of the terrain factors in the improved CASA model on the estimation results is confirmed. Finally, the improved CASA model and the CASA model are used to estimate the Net Primary Productivity (NPP) of the study area from 2000 to 2020, and the estimated results of the two models are compared with the computation results of the MODIS data NPP product. The findings indicate that the improved CASA model’s estimation results have a higher degree of fit and a better correlation. The improved CASA model aids in precisely understanding the ecological carbon sequestration potential of mountain areas and increases the estimation accuracy of vegetation carbon sequestration in mountainous areas.

Method for inverse calculation of erosion parameters in slag-refractory systems

Refractory erosion due to fluid flow is caused by the shear stresses acting on the liquid/solid interface. This mechanism of continuous wear has not been extensively investigated based on appropriate physical considerations. This study proposes a novel method for the inverse calculation of erosion parameters in slag-refractory systems. A computational fluid dynamic model is coupled with optimisation software to solve a nonlinear least-squares problem for the identification of erosion parameters from experimental erosion profiles. Erosion-rate modelling is performed based on a three-parameter law of the acting shear stress. A test problem is studied using artificially generated erosion profiles. The feasibility of the approach with two parameters is proven; however, using three parameters causes the problem to become ill-posed. Moreover, the method is successfully applied to a real experiment with an alumina coarse-grain refractory. Statistical analysis of the solutions is performed for both the test problem and real experimental profile. Confidence intervals and regions calculated via linearisation are examined, but their use is limited and should be evaluated for each case. This method can serve as a basis for further investigations concerning the quantification of refractory erosion. The data that support the findings of this study are available on reasonable request from the corresponding author.

Adaptive event‐triggered resilient stabilization for nonlinear semi‐Markov jump systems subject to DoS attacks

AbstractThis article investigates the problem of adaptive event‐triggered resilient stabilization for nonlinear semi‐Markov jump systems with DoS attacks. In this article, both DoS attacks and event‐triggered transmission strategy (ETTS) are considered. The DoS attacks may disturb the event‐triggered strategy, which implies that the original inequality condition of ETTS will no longer be satisfied. Different from the traditional ETTS, the adaptive ETTS is designed to reduce bandwidth usage. Based on the adaptive ETTS and resilient controller, the sufficient condition for stochastic stability of the closed‐loop system is proposed. Then, the calculation method of controller and observer parameters is given in the form of linear matrix inequality. Finally, the proposed adaptive event‐triggered resilient controller is applied to a single‐link robot arm model, which can show effectiveness of the proposed method.

Influences of thermal physical property parameters on operating characteristics of simulated rotating detonation ramjet fueled by C12H23

Two-phase rotating detonation ramjets are considered to be suitable for aerospace applications due to their high thermodynamic cycle efficiency. These engines have an extremely complex internal flow field, in which the liquid fuel undergoes physical and chemical processes such as fragmentation, evaporation, mixing, and combustion; these processes also interact with detonation waves that have significant gradients. This makes it difficult to simulate a three-dimensional (3D) full-process rotating detonation combustion chamber. Here, based on the Euler–Lagrangian simulation method, a 3D numerical combustion chamber was simulated using kinetic theory and the constant thermal physical property parameter (TPPP) calculation method. The accuracy of these methods was then compared with the existing experimental results and theoretical values. Calculating the TPPPs using kinetic theory brought about a relatively high-pressure peak and detonation wave temperature; the detonation wave profile was also finer and more precise. The detonation wave propagation velocity of the two-phase detonation is estimated to be about 60% of the theoretical gas-phase CJ velocity. The calculation method of physical parameters has relatively little influence on the engine’s operating frequency and the detonation wave's propagation velocity but has a more significant influence on the peak pressure. Constant TPPPs can be used when the Kelvin–Helmholtz–Rayleigh–Taylor model with insufficient precision is used to consider the breakup of droplets and leads to the acceleration of the propagation speed of two-phase detonation waves.

UWB channel modeling and simulation with continuous frequency response

Ultra-wideband (UWB) technology is a prospective technology for high-rate transmission and accurate localization in the future communication systems. State-of-art channel modeling approaches usually divide the UWB channel into several sub-band channels and model them independently. By considering frequency-dependent channel parameters, a novel analytical UWB channel model with continuous frequency response is proposed. The composite effect of all frequency components within the UWB channel on the channel impulse response (CIR) of delay domain is derived based on the continuous channel transfer function (CTF) of frequency domain. On this basis, a closed-form simulation model for UWB channels and geometry-based parameter calculation method are developed, which can guarantee the continuity of channel characteristics on the frequency domain and greatly reduce the simulation complexity. Finally, the proposed method is applied to generate UWB channel with 2 GHz bandwidth at sub-6GHz and millimeter wave (mmWave) bands, respectively. The channel measurements are also carried out to validate the proposed method. The simulated CIR and power gain are shown to be in good agreement with the measurement data. Moreover, the comparison results of power gain and Doppler power spectral density (DPSD) show that the proposed UWB channel model achieves a good balance between the simulation accuracy and efficiency.

Automatic alignment of standard views for transesophageal echocardiographic images.

3D transesophageal echocardiography (TEE) has become an important modality for pre- and peri-operative imaging of valvular heart disease. TEE can give excellent visualization of valve morphology in 3D rendering. As a convention, 3D TEE images are reformatted in three standard views. We describe a method for automatic calculation of parameters needed to define the standard views from 3D TEE images using no manual input. An algorithm was designed to find the center of the mitral valve and the left ventricular outflow tract (OT). These parameters defined the three-chamber view. The problem was modeled as a state estimation problem in which a 3D model was deformed based on shape priors and edge detection using a Kalman filter. This algorithm is capable of running in real time after initialization. The algorithm was validated by comparing the automatic alignments of 106 TEE images against manually placed landmarks. The median error for determining the mitral valve center was 7.1mm, and the median error for determining the left ventricular OT orientation was 13.5deg. The algorithm is an accurate tool for automating the process of finding standard views for TEE images of the mitral valve.

Influence analysis of calculated horizontally layered soil parameters on grounding parameters

AbstractCalculated parameters (soil layer resistivity, soil layer thickness, and the number of soil layers) of horizontally layered soil are usually obtained based on the measured apparent resistivity under different measurement distances, which are significant for the design, operation, and maintenance of grounding grids. Most existing calculation methods of soil parameters are just trying to make the calculation results approach the measurement data, ignoring the relationship among measurement data, the calculated soil parameters, and grounding parameters, which would increase the workload of the measurement. To better balance the distance range of the measurement data and the influence of the calculated horizontally layered soil on grounding parameters, this paper systematically studies the relationship among measured apparent soil resistivity, calculated horizontally layered soil parameters, and grounding parameters. The basic theories of apparent resistivity measurement, soil parameter calculation, and grounding parameter calculation are given, the influence of soil layer thickness on the measured apparent resistivity is studied, and the influence of the calculated soil parameters on the grounding resistance of different grounding models is analysed. Based on different scales of grounding grids, the results give a corresponding reference distance range of measured apparent soil resistivity. Therefore, this paper can help decrease the workload of soil resistivity measurement during grounding parameters analysis, which has far‐reaching engineering significance.

Oil generated overpressure of shale and its effect on tight sandstone oil enrichment: A case study of Yanchang Formation in the Ordos Basin, China

Oil generated overpressure (OGOP) is a key factor in tight sandstone oil enrichment. However, the relationship between the OGOP and oil enrichment remains unclear. On the basis of a physical simulation experiment and an oil injection experiment, an improved OGOP model based on the organic matter enrichment zone (OMEZ) was established, the attenuation of OGOP in shale was discussed, and the oil charging distance under different reservoir conditions was evaluated. The results showed that the OGOP starts from the OMEZ in the shale, is controlled by the OMEZ size, and decays during the expansion of the hydrocarbon expulsion microfractures. The attenuated OGOP acts as the initial migration force to push crude oil into tight sandstone reservoirs. The OGOP magnitude, OMEZ size and reservoir properties together determine the enrichment scale of tight sandstone oil. Driven by OGOP, the oil charging distance for the tight reservoir in the Yanchang Formation is only 66.7 m but 383.5 m for the conventional reservoir. These findings open a window to study the impact of shale internal structure on OGOP. The OGOP mathematical model and calculation method of various parameters in the process of oil accumulation proposed in this study are helpful for further understanding the mechanism of hydrocarbon generation, discharge, and enrichment.

An IGCT Unified Simulation Model Based on the Electrical Model and Thermistor

Integrated gate commutated thyristor (IGCT) is the core device of a new fusion power supply for Comprehensive Research Facility for Fusion Technology (CRAFT), which is very important to establish an accurate, suitable, and effective device model. To establish a unified simulation model (USM) suitable, this article analyzes the process of carrier motion in the process of IGCT turning on and off. The structure of the electrical model and the calculation method of related parameters are obtained by fitting the mathematical equations. Using standard passive components, such as resistance, capacitance, inductance, and an accurate bipolar junction transistor (BJT) model, converting the physical model into the electrical model can be realized. At the same time, because the physical model contains temperature parameters, compared with the traditional IGCT model, this model combines the thermal model with the electrical model, which makes the model unified. In this article, the 4000-A/4500-V IGCT power device in ABB is taken as an example to verify the rationality of the electric-thermal model under different currents and temperatures through MATLAB/SIMULINK simulation and experimental test.

Calculation method of hosiery knitting parameters based on three-dimensional mesh sampling

Custom socks, such as medical compression socks and hiking socks, are precisely designed and knitted according to the user's foot shape. However, developing styles of custom socks with commercial computer-aided design software requires workers to manually calculate the knitting parameters, and repeatedly adjust the knitting parameters through sample-making to meet the design requirements. We present a method to optimize the manual calculation and adjustment process of knitting parameters by using graphics technology. Our method converts a sock mesh model created by conventional modeling software into knitting parameters. Hosiery machines are able to knit socks with the same dimensions as the mesh based on the output parameters. Specifically, given user-defined top and toe markers on an input mesh, our system runs a sampling procedure over this mesh to gradually generate a knitting path that contains shape and dimension features of the mesh, and transforms the knitting path into knitting parameters for machine knitting. We demonstrated the feasibility of our method by knitting on a computerized hosiery machine. Filling the knitted socks with a soft foam model, we found that the knitted socks fit roughly well with the mesh surface, and the dimensional gap between the input mesh and the knitted socks (relaxed state) in several positions was below 4.90%.