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Equivalent Circuits of Dipole Antennas for Broadband Applications

APPLIED COMPUTATIONAL ELECTROMAGNETICS SOCIETY JOURNAL 2023年第4期38卷 240-250页

作者： Wang, Binwen Ning, Hui Yan, Youjie Cao, Chengyun Zhu, Meiqi Northwest Inst Nucl Technol Xian 710024 Peoples R China

In this paper distributed parameter equivalent circuits are developed for linear dipoles, dielectric coated dipoles and lumped loaded dipoles. Theoretical solutions for each distributed parameter and the reasonable non-uniform segmentation of antennas serve as the foundation for the derivation. The accomplished validations of the modeling procedures indicate that the given equivalent circuits are capable of correctly describing dipole antennas in frequency and time domains, with the advantages of wideband, frequency independence and unambiguous physical meaning. Relying on the presented equivalent circuits, broadband issues such as simulating input impedance, predicting equivalent lengths and computing transient responses of dipole antennas can be readily addressed. In addition, the circuit model provides helpful insights into the analysis and design for the loaded dipole antennas.

关键词： dipole antenna distributed parameter equivalent circuit non-uniform segmentation receiving antenna transient response.

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Inter-Turn Breakdown Fault Analysis and Winding Structure Optimisation of Winding of Dry-Type Transformers in Wind Farms

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ENERGIES 2023年第4期16卷 2012-2012页

作者： Pu, Ziheng Yu, Xinyun Wang, Yaoqiang Liu, Hao Feng, Zihao China Three Gorges Univ Coll Elect Engn & New Energy Yichang 443002 Peoples R China Hainan Jinpan Elect Res Inst Co Ltd Wuhan 430074 Peoples R China

To address the problem of winding turn-to-turn breakdown faults in 35 kV dry-type transformers in wind farms under overvoltage conditions, this paper establishes a simulation model based on the structural dimensions and material parameters of the transformer windings. The winding distribution parameters were calculated using the finite element method. The transient processes inside the high-voltage coil were calculated by constructing a multi-conductor transmission line model (MTL) that took into account the influence of the secondary winding. The voltage distribution of the winding was analysed for both lightning shock and extra-fast transient overvoltage conditions. The simulation results show that the maximum overvoltage between turns of the transformer winding under lightning shock is 5.282 kV;the maximum overvoltage between turns of the winding under very fast transient overvoltage is 11.6 kV, which occurs between the first 2-3 layers of the section, close to the insulation breakdown margin. On this basis, the transformer winding structure was optimised and the maximum inter-turn overvoltage after optimisation was 9.104 kV, reducing the likelihood of insulation breakdown by 24.1%. Finally, the accuracy of the winding structure optimisation simulation study was verified by testing the transformer's impulse voltage before and after optimisation, providing a reference for the stable operation of 35 kV dry-type transformers in wind farm practical applications.

关键词： dry type transformer ultra-fast transient overvoltage distributed parameter voltage distribution winding structure optimisation

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Effects of Spatial Resolution in Urban Hydrologic Simulations

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JOURNAL OF HYDROLOGIC ENGINEERING 2012年第1期17卷 129-137页

作者： Ghosh, Indrani Hellweger, Ferdi L. Northeastern Univ Dept Civil & Environm Engn Boston MA 02115 USA Kleinfelder SEA Consultants Cambridge MA 02142 USA

Model subdivision is used to capture spatial heterogeneity in input parameters and it is well-established that spatial resolution (i.e., degree of aggregation) affects model output. However, a general consensus about the effect does not exist. The objective of this study was to investigate the effects of spatial resolution on model predictions in an urban catchment, and to understand the mechanism(s) responsible for the scale effect. The general approach is to develop models at various spatial resolutions, perform simulations, and compare the predictions of total outflow volume and peak flow. Models were developed on the basis of actual drainage networks, and artificial ones generated on the basis of a fractal algorithm by using the Artificial Network Generator (ANGel). Simulations were performed by using the EPA Storm Water Management Model (SWMM), and model output was compared for 50 storms. There was very little difference in the total annual outflow volumes predicted by the different resolutions. However, peak flows showed a dual scale effect. For the larger storms, model aggregation reduced peak flows, which can be explained by differences in infiltration. This effect was attributed primarily to the spatial distribution of the soil-saturated hydraulic conductivity and the length of overland flow. For the smaller storms, aggregation increased peak flows, which can be explained by the combined effects of overland flow and conduit routing. The results were consistent using actual and artificial networks. This study illustrates that a scale effect can be introduced by different processes, which can go in different directions (i.e. increase or decrease peak flows) and depend on the storm characteristics. DOI: 10.1061/(ASCE)HE.1943-5584.0000405. (C) 2012 American Society of Civil Engineers.

关键词： Hydrologic model Urban area Artificial sewer networks Scale effect distributed parameter Routing

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Pulsatile cerebrospinal model with cardio-vascular coupling

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IFAC-PapersOnLine 2015年第20期48卷 183-188页

作者： Berno J.E. Misgeld Rajib Mondal Steffen Leonhardt Philips Chair for Medical Information Technology Helmholtz-Institute RWTH Aachen University 52074 Aachen Germany

In this paper we describe a model of the human intracranial space which is extended with the vascular system. We focus on a detailed modelling of the coupling between cerebral vessels and intracranial pressure (ICP). On the one hand, the model is based on a linearisation of the Navier-Stokes equation for the blood vessels and a subsequent geometric discretisation, leading to a distributed parameter approach of coupled ordinary differential equations. On the other hand, a concentrated parameter modelling approach is developed for the intracranial space which is subsequently extended by a production and resorption circuit for the craniospinal fluid. The intention of the model is to describe the transmission of pulsatile blood pressure waves from the cerebral vessels to the ICP, as it can be observed from clinical continuous intracranial pressure measurements. A good agreement of pulsatile ICP is shown in an in-silico study, compared to clinical continuous ICP measurements. An analysis of vascular impedance under variable intracranial compliance and for a non-symmetric Circle-of-Willis completes this study.

关键词： Hydrocephalus biomedical modelling cranio-spinal compliance intracranial pressure distributed parameter

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DYNAMIC-MODEL OF A FLUIDIZED-BED DRYER

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DRYING TECHNOLOGY 1993年第3期11卷 589-602页

作者： PANDA, RC RAO, VSR Indian Inst of Technology Madras India

An axially distributed dynamic model of a gas-solid continuous fluidized bed dryer is *** steady state form of the model is compared with the existing models. Through simulation profiles of the moisture content and temperature of the bed are obtained. The transient analysis of the developed model is studied with reference to step changes in the air inlet temperature, superficial air velocity, particle residence time, initial moisture content of the feed and dryer-wall temperature. The results are useful in developing precise control strategies to implement on the fluidized bed dryer.

关键词： AUTOMATIC CONTROL distributed parameter DYNAMIC CHARACTERISTICS MOISTURE AND TEMPERATURE PROFILES

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Ventricle Boundary in CT: Partial Volume Effect and Local Thresholds

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INTERNATIONAL JOURNAL OF BIOMEDICAL IMAGING 2010年第unknown期2010卷 6p-6p页

作者： Volkau, Ihar Puspitasari, Fiftarina Nowinski, Andwieslaw L. ASTAR Biomed Imaging Lab 30 Biopolis St07-01 Matrix 138671 Singapore

We present a mathematical frame to carry out segmentation of cerebrospinal fluid (CSF) of ventricular region in computed tomography (CT) images in the presence of partial volume effect (PVE). First, the image histogram is fitted using the Gaussian mixture model (GMM). Analyzing the GMM, we find global threshold based on parameters of distributions for CSF, and for the combined white and grey matter (WGM). The parameters of distribution of PVE pixels on the boundary of ventricles are estimated by using a convolution operator. These parameters are used to calculate local thresholds for boundary pixels by the analysis of contribution of the neighbor pixels intensities into a PVE pixel. The method works even in the case of an almost unimodal histogram;it can be useful to analyze the parameters of PVE in the ground truth provided by the expert.

关键词： image histogram cisplatin/vinblastine Boundary Gm(m) X-Ray Computed Tomography pixel ground truth global thresholding distributed parameter

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Influence of Model of Circuit-breaker on Very Fast Transient Over-voltage

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Physics Procedia 2012年 24卷 283-289页

作者： Wang Na Liang Yu School of Information Engineering Shenyang University of Chemical Technology Shenyang University of Technology Shenyang China

Based on a power station, two transient models of circuit-breaker is employed and the very fast transient over-voltage in 550kVGIS is calculated and simulated in the consideration of two different models of circuit-breaker, applying the Electro-Magnetic Transient Program in this paper. The impact of varied models on the values and the frequencies of VFTO in the GIS is intensively focused. It is indicated that the two models of circuit breaker have different effects on the peak voltage of VFTO for different nodes. Under the two operation modes, the deviations of the most voltage spectrum frequency are 5.8% and 0 at circuit breaker. Comparing to the results of the two operation modes, the deviation of operating DS21 are higher than that of operating DS22 because of the changing current flow.

关键词： Circuit- breaker distributed parameter VFTO disconnector switchIntroduction

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Bayesian Analysis of Item Response Models Using WinBUGS 1.4.3

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APPLIED PSYCHOLOGICAL MEASUREMENT 2012年第2期36卷 147-148页

作者： Cho, Sun-Joo Suh, Youngsuk Vanderbilt Univ Peabody Coll Nashville TN 37203 USA Rutgers State Univ New Brunswick NJ 08903 USA

WinBUGS 1.4.3 (Spiegelhalter, Thomas, & Best, 2003) language is a syntax to generate a random sample from the posterior distribution of the parameters of a Bayesian model. WinBUGS users only have to specify the structure of the model, initial values (optional), and the data. WinBUGS 1.4.3 codes for both simple and complex item response models are provided. Considered models include a Rasch model, a two-parameter item response model, a partial credit model, a multilevel Rasch model, a compensatory multidimensional Rasch model, and a mixture Rasch model. The specification of the multilevel, multidimensional, or mixture structures are illustrated within the framework of the Rasch model. Readers can simply extend these models to more complex models that include item discrimination and item guessing parameters by referring to codes for two-parameter or three-parameter item response models. Using empirical data, results from WinBUGS 1.4.3 are compared with those from other existing software packages using different estimation algorithms (e.g., marginal maximum likelihood estimation and Laplace approximation). For a simulation study, data can be generated by fixing the generating parameters in the WinBUGS code, running the program for a single iteration, and then saving the current state of the sampler for the item responses (Spiegelhalter, personal communication, September 30, 2005). Example codes for the data generation and a batch mode for replications in the simulation study are provided.

关键词： samplers current status MULTIDIMENSIONAL Posterior distribution maximum likelihood estimation Software packages distributed parameter Model structures data generation empirical data Item Response Theory syntax Bayes methods Codes random sample

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DEVELOPMENT OF WATERSHED MODELS FOR 2 SIERRA-NEVADA BASINS USING A GEOGRAPHIC INFORMATION-SYSTEM

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WATER RESOURCES BULLETIN 1993年第6期29卷 923-932页

作者： JETON, AE SMITH, JL US Geol.Surv. 333 W Nye LaneCarson CityNV 89706 United States

Techniques were developed using vector and raster data in a geographic information system (GIS) to define the spatial variability of watershed characteristics in the north-central Sierra Nevada of California and Nevada and to assist in computing model input parameters. The U.S. Geological Survey's Precipitation-Runoff Modeling System, a physically based, distributed-parameter watershed model, simulates runoff for a basin by partitioning a watershed into areas that each have a homogeneous hydrologic response to precipitation or snowmelt. These land units, known as hydrologic-response units (HRU's), are characterized according to physical properties, such as altitude, slope, aspect, land cover, soils, and geology, and climate patterns. Digital data were used to develop a GIS data base and HRU classification for the American River and Carson River basins. The following criteria are used in delineating HRU's: (1) Data layers are hydrologically significant and have a resolution appropriate to the watershed's natural spatial variability, (2) the technique for delineating HRU's accommodates different classification criteria and is reproducible, and (3) HRU's are not limited by hydrographic-subbasin boundaries. HRU's so defined are spatially noncontiguous. The result is an objective, efficient methodology for characterizing a watershed and for delineating HRU's. Also, digital data can be analyzed and transformed to assist in defining parameters and in calibrating the model.

关键词： WATERSHED MODEL VECTOR AND RASTER DATA distributed parameter HYDROLOGIC-RESPONSE UNIT GEOGRAPHIC INFORMATION SYSTEM PATTERN IDENTIFICATION NUMBER

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Using a Parallel Helical Sensing Cable for the distributed Measurement of Ground Deformation

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SENSORS 2019年第6期19卷 1297.-1297.页

作者： Wu, Xiushan Tong, Renyuan Wang, Yanjie Mei, Congli Li, Qing Zhejiang Univ Water Resources & Elect Power Sch Elect Engn Hangzhou 310018 Peoples R China China Jiliang Univ Coll Mech & Elect Engn Hangzhou 310018 Peoples R China

Surface and underground stretched deformation is one of the most important physical measurement quantities for geological-disaster monitoring. In this study, a parallel helical sensing cable (PHSC) based on the time-domain reflectometry (TDR) technique is proposed and used to monitor large ground stretched deformation. First, the PHSC structure and manufacturing process are introduced, and then, distributed capacitance, distributed inductance, and characteristic impedance were derived based on the proposed stretched-structure model. Next, the relationship between characteristic impedance and stretched deformation was found, and the principle of distributed deformation measurement based on the TDR technique and PHSC characteristic impedance was analyzed in detail. The function of the stretched deformation and characteristic impedance was obtained by curve fitting based on the theoretically calculated results. A laboratory calibration test was carried out by the designed tensile test platform. The results of multi-point positioning and the amount of stretched deformation are presented by the tensile test platform, multi-point positioning measurement absolute errors were less than 0.01 m, and the amount of stretched deformation measurement absolute errors were less than 3 mm, respectively. The measured results are in good agreement with the theoretically calculated results, which verify the correctness of theoretical derivation and show that a PHSC is very suitable for the distributed measurement of the ground stretched deformation.

关键词： geological monitoring parallel helical sensing cable time-domain reflectometry (TDR) distributed parameter characteristic impedance stretched deformation

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