scholarly journals STREAMER MODE OF POSITIVE CORONA

2021 ◽  
pp. 166-170
Author(s):  
O.V. Bolotov ◽  
B.B. Kadolin ◽  
S.M. Mankovskyi ◽  
V.M. Ostroushko ◽  
I.A. Pashchenko ◽  
...  
Keyword(s):  
Simplified Model ◽  
Constant Voltage ◽  
Space Size ◽  
Streamer Propagation ◽  
Calculation Results ◽  
Partial Release ◽  
Streamer Mode

One cycle of quasi-periodic streamer mode of positive corona at constant voltage is considered. The calculation results for the streamer propagation at a voltage near to threshold of the streamer mode and for the stage of partial release of the gap from the ions are presented. The simplified model of ionization development near the anode before the start of the next streamer is considered and it is estimated the ionized space size, from which the streamer propagation begins.

Research on the Model-Building Error for EMS Maglev Vehicles

2014 ◽  
Vol 701-702 ◽  
pp. 757-760
Author(s):  
Xiao Zhang ◽  
Jun Yong Lu ◽  
Xin Lin Long
Keyword(s):  
Model Building ◽  
Simplified Model ◽  
Modeling Error ◽  
New Methods ◽  
Calculation Results

To estimate the influences of uncertain factors on the modeling error of maglev vehicles, the single electro-magnet is taken as the object in this paper. Researches on the model-building error are carried out, including factors of the uncertainty of the inductor, the elasticity of the guideway and the coupling between Modules. Also, the model-building errors are analyzed numerically from the view of L∞ norm. And the calculation results are presented, which shows severe model-building severe error with the simplified model. The results are revelatory to comprehend the phenomena of the vehicle’s vibration, and to search after new methods of levitation control for EMS maglev vehicles.

Radio emission from fast streamers

2020 ◽  
Author(s):  
Nikolai Lehtinen
Keyword(s):  
Electric Field ◽  
External Electric Field ◽  
Electron Attachment ◽  
Computational Method ◽  
Radio Emissions ◽  
Streamer Propagation ◽  
Streamer Length ◽  
Calculation Results ◽  
External Conditions ◽  
Lightning Initiation

<p>A new computational approach, based on treating an electric streamer as a nonlinear instability, allows to determine unambiguously its parameters, for a given streamer length and external electric field, which may be nonuniform. Among the determined parameters are the speed, current and conductivity inside the streamer. These parameters may vary over orders of magnitude, depending on external conditions.</p><p>We use these parameters to calculate the radio emissions which would be observed on the ground from fast discharges produced in lightning, in which streamer velocities approach a significant fraction of the speed of light. Fast discharges play an important role in lightning initiation and may be responsible for production of Terrestrial Gamma Flashes (TGF). They manifest themselves in ground-based radio observations as Narrow Bipolar Events (NBE), to which the calculation results are compared.</p><p>We will discuss conditions, the effect of which on streamer propagation (and therefore electromagnetic radiation) may be quantified with the used computational method. These include (i) the external electric field modification due to charges deposited by previous streamers; and (ii) electron attachment inside the streamer channel, which is strongly affected by cloud humidity.</p>

Study on the Hydration Kinetics of Portland Cement

2013 ◽  
Vol 539 ◽  
pp. 30-34
Author(s):  
Wei Wang ◽  
Wu Yao ◽  
Yong Qi Wei
Keyword(s):  
Portland Cement ◽  
Reaction Rate ◽  
Isothermal Calorimetry ◽  
Simplified Model ◽  
Hydration Kinetics ◽  
Hydration Mechanism ◽  
Degree Of Reaction ◽  
Calculation Results ◽  
Simple Equations ◽  
Boundary Reaction

A kinetic model originally developed by Tomosawa is analyzed for the hydration of Portland cement. The complicated kinetic equation of Tomosawa model is transformed into three simple equations of simplified model which represent mass transfer, phase-boundary reaction and diffusion process at different stage, respectively. Based on the isothermal calorimetry and the simplified model, the relationship between the degree of reaction and reaction rate is discussed. The derived result could reflect the development of degree of reaction and reaction rate during the cement hydration. The calculation results of simplified model are compared well with the experimental results. Studying the connection among the three processes is helpful to understanding the complicated hydration mechanism of Portland cement.

The Simplified Method for Stress Analysis on Tubesheet of Fixed Tubular Heat Exchanger With Expansion Joint

2011 ◽  
Author(s):  
Lin Zhou ◽  
Xiaohua He ◽  
Changyu Zhou ◽  
Xiaoping Zhang
Keyword(s):  
Heat Exchanger ◽  
Waste Heat ◽  
Design Method ◽  
Simplified Model ◽  
Application Research ◽  
Ansys Software ◽  
Tubular Heat Exchanger ◽  
Expansion Joints ◽  
Simplified Method ◽  
Calculation Results

The simplified FEA method was proposed on tubesheet of fixed tubular heat exchanger with bellows expansion joints. Taking the waste heat recovery heat exchanger for example, the entire model and the simplified model were established using ANSYS software, and the calculation results of the key components of the two models were compared. The results show that distribution of TRESCA stress intensity and radial displacement of tubesheet for the simplified model are consistent with those of the whole model, but the stress of the simplified model is slightly larger than that of the entire model, so the result is conservative. It means that the simplified method is feasible. Meanwhile, application research on tubesheet of different kinds of heat exchanger was made using the simplified design method, it provides an efficient FEA method of the tubesheet design for heat exchanger with expansion joints.

scholarly journals Static and Dynamic Analysis of Railway Reinforced System with Cross-Beams

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Bin Peng ◽  
Nan Zhang ◽  
Yu Lan Gao
Keyword(s):  
Dynamic Analysis ◽  
Resonance Phenomenon ◽  
Simplified Model ◽  
Construction Site ◽  
Design Requirement ◽  
Interaction Method ◽  
Static And Dynamic Analysis ◽  
Calculation Results ◽  
Optimized Model ◽  
Reinforcement Design

To fulfill the design requirement of railway reinforced system with cross-beams, the model for the static analysis of the railway reinforced system is optimized, the dynamic response is calculated by the vehicle-rail interaction method, the standards of both static and dynamic analysis are established, and the calculation results of many cases with different parameters are evaluated. It is found that, compared with simplified model, the optimized model simulated the conditions of construction site better, so that results are improved; the acceleration and the offloading factor of reinforced system is obtained by the dynamic analysis, whose vibration and resonance phenomenon can be simulated. The calculated result and the railway reinforcement design are safer by adopting the proposed standard in both static and dynamic analysis.

The Modal Analysis of Roller Chain Drives

2011 ◽  
Vol 291-294 ◽  
pp. 1551-1554 ◽  
Author(s):  
Bao Lin Li ◽  
Shuai Fan ◽  
Yan Zhang
Keyword(s):  
Numerical Simulation ◽  
Theoretical Calculation ◽  
Natural Frequency ◽  
Engineering Application ◽  
Simplified Model ◽  
Harmonic Response ◽  
Roller Chain ◽  
Calculation Results ◽  
Chain Drives ◽  
Ansys Workbench

Aiming at calculating the natural frequency of roller chain drives, the software Catia was used for modeling the roller chain drives accurately and Ansys Workbench was applied to analyze the modal and harmonic response of the tension side chains, comparing the natural frequency and the theoretical calculation results of simplified model. The results showed that the deviation increased with the increase of the order of natural frequency and modal numerical simulation provides certain reference for engineering application.

Study on Measurement and Simplified Model of Burning Rate of AP/HTPB Base Bleed Propellant under High Pressure

2013 ◽  
Vol 724-725 ◽  
pp. 1176-1180 ◽  
Author(s):  
Hui Shen ◽  
Yong Gang Yu
Keyword(s):  
High Pressure ◽  
Burning Rate ◽  
Experimental Results ◽  
Simplified Model ◽  
Combustion Theory ◽  
Calculation Results ◽  
Htpb Propellant ◽  
Base Bleed ◽  
Good Agreement

In order to understand the burning rate of AP/HTPB propellant of the base bleed unit, the p-t curves of combustion of AP/HTPB base bleed propellant are measured in the closed bomb. The burning rate formula of the propellant under 50-200MPa is obtained by fitting to the experimental results. Based on division zone combustion theory, a simplified model of the burning rate of AP/HTPB base bleed propellant under high pressure is established. The calculation results and the experimental results are in good agreement.

The Finite Element Model Improvement on Shear Behavior of RC Frame Columns under Lateral Bevel Load

2012 ◽  
Vol 468-471 ◽  
pp. 2609-2612
Author(s):  
Chuang Du ◽  
Xi Kang Yan ◽  
Hai Long Zhao
Keyword(s):  
Finite Element ◽  
Element Model ◽  
Computer Time ◽  
Shear Capacity ◽  
Simplified Model ◽  
Finite Element Models ◽  
Rc Frame ◽  
Calculation Results ◽  
Model Improvement ◽  
The Finite Element Model

The finite element models of biaxial shear capacity of RC frame columns are investigated.The calculation results and experimental results are compared using the different models.It is shown that different finite element models are effectively used to simulate the RC frame column. However, the simplified model may save computer time and be more convenient for the numerical simulation. Finally, the bilateral shear correlation of RC frame column is investigated using the simplified model. The results indicate that the bilateral shear correlation of the RC frame columns with different quantity of stirrups in two directions accords with the ellipse law and the fitting formula is presented.

Effects of Gender, Parental Role, and Time on Infant- and Adult-Directed Read and Spontaneous Speech

2019 ◽  
Vol 62 (11) ◽  
pp. 4001-4014
Author(s):  
Melanie Weirich ◽  
Adrian Simpson
Keyword(s):  
Parental Involvement ◽  
Gender Identity ◽  
Spontaneous Speech ◽  
First Year ◽  
Space Size ◽  
Vowel Space ◽  
Potential Impact ◽  
Phonetic Features ◽  
And Gender ◽  
Description Task

Purpose The study sets out to investigate inter- and intraspeaker variation in German infant-directed speech (IDS) and considers the potential impact that the factors gender, parental involvement, and speech material (read vs. spontaneous speech) may have. In addition, we analyze data from 3 time points prior to and after the birth of the child to examine potential changes in the features of IDS and, particularly also, of adult-directed speech (ADS). Here, the gender identity of a speaker is considered as an additional factor. Method IDS and ADS data from 34 participants (15 mothers, 19 fathers) is gathered by means of a reading and a picture description task. For IDS, 2 recordings were made when the baby was approximately 6 and 9 months old, respectively. For ADS, an additional recording was made before the baby was born. Phonetic analyses comprise mean fundamental frequency (f0), variation in f0, the 1st 2 formants measured in /i: ɛ a u:/, and the vowel space size. Moreover, social and behavioral data were gathered regarding parental involvement and gender identity. Results German IDS is characterized by an increase in mean f0, a larger variation in f0, vowel- and formant-specific differences, and a larger acoustic vowel space. No effect of gender or parental involvement was found. Also, the phonetic features of IDS were found in both spontaneous and read speech. Regarding ADS, changes in vowel space size in some of the fathers and in mean f0 in mothers were found. Conclusion Phonetic features of German IDS are robust with respect to the factors gender, parental involvement, speech material (read vs. spontaneous speech), and time. Some phonetic features of ADS changed within the child's first year depending on gender and parental involvement/gender identity. Thus, further research on IDS needs to address also potential changes in ADS.

Clearance and In Vivo Release by Heparin of Human Platelet Factor 4 (PF4) in the Rabbit

1984 ◽  
Vol 52 (02) ◽  
pp. 157-159 ◽  
Author(s):  
M Prosdocimi ◽  
N Scattolo ◽  
A Zatta ◽  
F Fabris ◽  
F Stevanato ◽  
...  
Keyword(s):  
Half Life ◽  
Human Platelet ◽  
Slow Component ◽  
Platelet Factor 4 ◽  
Platelet Factor ◽  
In Vivo Release ◽  
Partial Release ◽  
Different Doses ◽  
New Zealand Rabbits

Summary13 male New Zealand rabbits were injected with two different doses (25 μg/Kg and 100 μg/Kg) of human platelet factor 4 antigen (PF4). The disappearance of the protein was extremely fast with an half-life for the fast component of 1.07 ± 0.16 and 1.76 ± 0.11 min respectively. The half-life for the slow component, detectable only with the highest dosage, was 18.8 min.The administration of 2500 I.U. of heparin 30 min after PF4 administration induced a partial release of the injected protein and its clearance from plasma was slow, with half-life of 23.3 ± 5.9 min and 30.9 ± 2.19 min respectively.

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