Determination of thermal parameters of non-spherical particles in a packed bed from svstem response analysis in the time domain

1994 ◽  
Vol 72 (4) ◽  
pp. 602-606 ◽  
Author(s):  
H. D. Doan ◽  
R. B. Brown ◽  
V. J. Davidson ◽  
L. Otten
Keyword(s):  
Time Domain ◽  
Packed Bed ◽  
Thermal Parameters ◽  
Spherical Particles ◽  
Response Analysis ◽  
The Time Domain

scholarly journals Distribution of Characteristic Times: A High-Resolution Spectrum Approach for Visualizing Chemical Relaxation and Resolving Kinetic Parameters of Ionic-Electronic Conducting Ceramic Oxides

Coatings ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1240
Author(s):  
Fuyao Yan ◽  
Yiheng Wang ◽  
Ying Yang ◽  
Lei Zhu ◽  
Hui Hu ◽  
...  
Keyword(s):  
Kinetic Parameters ◽  
Time Domain ◽  
Bulk Diffusion ◽  
High Resolution Spectrum ◽  
Surface Exchange ◽  
Ceramic Oxides ◽  
Fitting Procedure ◽  
The Time Domain ◽  
Rate Limiting

Surface exchange coefficient (k) and bulk diffusion coefficient (D) are important properties to evaluate the performance of mixed ionic-electronic conducting (MIEC) ceramic oxides for use in energy conversion devices, such as solid oxide fuel cells. The values of k and D are usually estimated by a non-linear curve fitting procedure based on electrical conductivity relaxation (ECR) measurement. However, the rate-limiting mechanism (or the availability of k and D) and the experimental imperfections (such as flush delay for gaseous composition change, τf) are not reflected explicitly in the time–domain ECR data, and the accuracy of k and D demands a careful sensitivity analysis of the fitting error. Here, the distribution of characteristic times (DCT) converted from time–domain ECR data is proposed to overcome the above challenges. It is demonstrated that, from the DCT spectrum, the rate-limiting mechanism and the effect of τf are easily recognized, and the values of k, D and τf can be determined conjunctly. A strong robustness of determination of k and D is verified using noise-containing ECR data. The DCT spectrum opens up a way towards visible and credible determination of kinetic parameters of MIEC ceramic oxides.

Analysis of Brief Tension Loss in TLP Tethers

1988 ◽  
Vol 110 (1) ◽  
pp. 43-47 ◽  
Author(s):  
J. N. Brekke ◽  
T. N. Gardner
Keyword(s):  
Time Domain ◽  
Large Diameter ◽  
Nonlinear Effects ◽  
Response Analysis ◽  
Bending Stress ◽  
Large Wave ◽  
Wave Trough ◽  
Design Selection ◽  
The Time Domain ◽  
Selection Of

The avoidance of “slack” tethers is one of the factors which may establish the required tether pretension in a tension leg platform (TLP) design. Selection of an appropriate safety factor on loss of tension depends on how severe the consequences may be. It is sometimes argued that if tethers go slack, the result may be excessive platform pitch or roll motions, tether buckling, or “snap” or “snatch” loading of the tether. The results reported here show that a four-legged TLP would not be susceptible to larger angular motions until two adjacent legs lose tension simultaneously. Even then, this analysis shows that a brief period of tether tension loss (during the passage of a large wave trough) does not lead to excessive platform motion. Similarly, momentary tension loss does not cause large bending stress in the tether or significant tension amplification as the tether undergoes retensioning. This paper presents TLP platform and tether response analysis results for a representative deepwater Gulf of Mexico TLP with large-diameter, self-buoyant tethers. The time-domain, dynamic computer analysis included nonlinear effects and platform/tether coupling.

On the Evaluation of Dynamic Stresses in Pipelines Using Limited Vibration Measurements and FEA in the Time Domain

1999 ◽  
Vol 121 (1) ◽  
pp. 37-41 ◽  
Author(s):  
W. A. Moussa ◽  
A. N. AbdelHamid
Keyword(s):  
Time Domain ◽  
Minimum Distance ◽  
Exciting Force ◽  
Vibration Measurement ◽  
Dynamic Stresses ◽  
Vibration Measurements ◽  
Pipe Model ◽  
Related Risk ◽  
The Time Domain

A practical technique is investigated for the determination of dynamic stresses in pipelines through the use of finite element method (FEM) and field measurement vibrations at selected points. Numerical simulation of a randomly loaded pipeline structure is used to establish the validity of the technique in the time domain. The analysis is carried out for a fixed-hinged pipe model. The results show that lack of coincidence between the vibration measurement points (VMPs) and the exciting force, or the use of only translational vibration measurements (TVMs) produce an approximate stress picture. The extent of the “error” in these cases is found to depend on the density of the VMPs and the proximity between these points and the exciting force location. A safety-related risk assessment is applied to find the minimum distance between measuring points that is needed to meet design codes reliability specifications.

scholarly journals Determination of Mount Merapi Volcanic Earthquake Hypocentre By Using Seismic Wave Polarization Analysis

2020 ◽  
Vol 1 (1) ◽  
pp. 21
Author(s):  
Syahrial Ayub ◽  
Muhammad Zuhdi ◽  
Muhammad Taufik ◽  
Gunawan Gunawan
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Volcanic Earthquake ◽  
Wave Polarization ◽  
Polarization Analysis ◽  
Space Domain ◽  
Volcanic Earthquakes ◽  
Hypocenter Determination ◽  
The Time Domain

Volcanic earthquakes of mount Merapi have been investigated periodically. The investigation aims to determine the hypocenter and epicenter of mount Merapi's volcanic earthquake using wave polarization analysis. The analysis was carried out in three domains, which are the time domain, the frequency domain, and the space domain. The analysis in the time domain was conducted by the arrival time of the volcanic earthquake, and the analysis in the frequency domain was done by observing the spectrum to get information on source frequency and bandwidth passed from polarization analysis, while the analysis in the space domain was conducted especially on hypocenter determination of the volcanic earthquakes. The analysis leads to the frequency of source 6 Hz and a bandwidth of 0.1 Hz. Thus, the hypocenter of volcanic earthquakes by polarization analysis was distributed to depth from 670 m to 3250 m from Merapi's top

Dynamic Response Analysis of a Triangular Tension Leg Platform

2015 ◽  
Author(s):  
Qiang Guo ◽  
Gang Ma ◽  
Liping Sun ◽  
Hongwei Wang ◽  
Na Cui
Keyword(s):  
Time Domain ◽  
Three Dimensional ◽  
Response Analysis ◽  
Mooring System ◽  
Preliminary Design ◽  
Tension Leg Platform ◽  
Operation Conditions ◽  
Motion Responses ◽  
Tendon Tension ◽  
The Time Domain

The tension leg platform is widely used in the world. In this paper, a newly developed tension leg platform is evaluated under the environment loads of the South China Sea. The focus is on the coupling response of the platform hull and tendons. The three dimensional potential theory is used to analyze the new developed tension leg platform and its mooring system in the time domain. The new developed TLP is in a triangular-shape with three group tension legs. Every group consists of five tendons; the mooring system has been optimized after preliminary design. Coupling analysis in time domain has been conducted to evaluate its motion and tendon tension under different environmental loads. The results demonstrate the great improvement in the motion responses of this new developed TLP. The coupled motion responses of this platform with tendon lines system in extreme environmental conditions have also been evaluated in order to evaluate the safety in operation conditions.

NUMERICAL FREQUENCY RESPONSE ANALYSIS OF SWITCHING CONVERTERS BEHAVIORAL MODELS

2019 ◽  
Author(s):  
Aleksey Shkolin
Keyword(s):  
Time Domain ◽  
Nonlinear Dynamic ◽  
Frequency Characteristics ◽  
Response Analysis ◽  
Switching Converters ◽  
Behavioral Models ◽  
Pulse Converter ◽  
Signal Mode ◽  
The Time Domain ◽  
Simulated Object

This work is devoted to a method for numerically determining the frequency characteristics when modeling nonlinear dynamic objects, in particular during behavioral modeling of pulse converter circuits. The analysis of existing methods for modeling the frequency characteristics of pulse converters is carried out. A technique is given for reducing the amount of calculations when calculating the frequency characteristics of models of nonlinear dynamic pulse systems in the field of their stability based on a calculation in the time domain. This allows one to take into account the essential features of the studied nonlinear objects, in contrast to the linearized models applicable only to the small signal mode. The method is based on the use of correlation analysis when finding the steady-state stationary motion of the simulated object in the time domain while varying the frequency of the harmonic input signal. The results of modeling using the proposed approach are presented.

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