Time Moment Models

2019 ◽  
pp. 43-62
Author(s):  
Allamaraju Subrahmanyam ◽  
Ganti Prasada Rao
Keyword(s):  
Time Moment ◽  
Moment Models

Parameter Determination for Chloride and Tritium Transport in Undisturbed Lysimeters during Steady Flow

1992 ◽  
Vol 23 (2) ◽  
pp. 89-104 ◽  
Author(s):  
Ole H. Jacobsen ◽  
Feike J. Leij ◽  
Martinus Th. van Genuchten
Keyword(s):  
Experimental Data ◽  
Unsaturated Flow ◽  
Transport Model ◽  
Time Moment ◽  
Breakthrough Curves ◽  
Coarse Sand ◽  
Retardation Factor ◽  
Parameter Determination ◽  
Model Parameters ◽  
Water Fraction

Breakthrough curves of Cl and 3H2O were obtained during steady unsaturated flow in five lysimeters containing an undisturbed coarse sand (Orthic Haplohumod). The experimental data were analyzed in terms of the classical two-parameter convection-dispersion equation and a four-parameter two-region type physical nonequilibrium solute transport model. Model parameters were obtained by both curve fitting and time moment analysis. The four-parameter model provided a much better fit to the data for three soil columns, but performed only slightly better for the two remaining columns. The retardation factor for Cl was about 10 % less than for 3H2O, indicating some anion exclusion. For the four-parameter model the average immobile water fraction was 0.14 and the Peclet numbers of the mobile region varied between 50 and 200. Time moments analysis proved to be a useful tool for quantifying the break through curve (BTC) although the moments were found to be sensitive to experimental scattering in the measured data at larger times. Also, fitted parameters described the experimental data better than moment generated parameter values.

scholarly journals Modeling Operation of Liquid Metal Fuses When Breaking Overcurrents

2020 ◽  
Vol 178 ◽  
pp. 01060
Author(s):  
A V Kuznetsov ◽  
D S Aleksandrov ◽  
Y P Yurenkov
Keyword(s):  
Liquid Metal ◽  
Short Circuit ◽  
Time Moment ◽  
Circuit Breaker ◽  
Reference Points ◽  
Joint Operation ◽  
Pilot Studies ◽  
In Series ◽  
Current Limiter ◽  
Temperature Melting

This paper shows that successful switching of extremely high short-circuit currents I> 50 kA can be achieved by joint operation of a liquid-metal self-resetting current limiter and a circuit breaker connected in series. The type NFU-225 device from Mitsubishi was taken as an example. The time-current characteristic of joint operation of a liquid-metal self-resetting current-limiting device and a circuit breaker was compiled. However, further in the article physical processes occurring in a liquid-metal self-resetting current limiter with a complete transformation of fusible unit are considered. The result of work is modelling of operation of liquid-metal fuses when overcurrents are switched off based on the pilot studies obtained by the Japanese scientists. It is proposed to simulate the break process not at every time moment, but at specific time moments (reference points). At other time moments, current and voltage should be considered as approximately linearly changing characteristics. The work of current limiter can be represented by three stages: the pre-arc, the main arc and the final arc. If the current density is less than 1000 A/mm2, then the pre-arc operation stage of the current limiter includes the following sections for heating the fusible unit: primary heating to the melting temperature; melting and its transition to liquid state; secondary heating to evaporation temperature; evaporation of fusible unit.

scholarly journals Supervised linear classification of Gaussian spatio-temporal data

2021 ◽  
Vol 62 ◽  
pp. 9-15
Author(s):  
Marta Karaliutė ◽  
Kęstutis Dučinskas
Keyword(s):  
Time Moment ◽  
Gaussian Random Field ◽  
Covariance Structure ◽  
Simulated Data ◽  
Spatial Location ◽  
Error Rates ◽  
Prior Probabilities ◽  
Structure Factors ◽  
Spatio Temporal

In this article we focus on the problem of supervised classifying of the spatio-temporal Gaussian random field observation into one of two classes, specified by different mean parameters. The main distinctive feature of the proposed approach is allowing the class label to depend on spatial location as well as on time moment. It is assumed that the spatio-temporal covariance structure factors into a purely spatial component and a purely temporal component following AR(p) model. In numerical illustrations with simulated data, the influence of the values of spatial and temporal covariance parameters to the derived error rates for several prior probabilities models are studied.

scholarly journals On the construction of resolving control in the problem of getting close at a fixed time moment

2021 ◽  
Vol 58 ◽  
pp. 73-93
Author(s):  
V.N. Ushakov ◽  
A.V. Ushakov ◽  
O.A. Kuvshinov
Keyword(s):  
Euclidean Space ◽  
Compact Space ◽  
Time Moment ◽  
Fixed Time ◽  
Dimensional Euclidean Space ◽  
Controlled System ◽  
Finite Dimensional ◽  
Solvability Set

The problem of getting close of a controlled system with a compact space in a finite-dimensional Euclidean space at a fixed time is studied. A method of constructing a solution to the problem is proposed which is based on the ideology of the maximum shift of the motion of the controlled system by the solvability set of the getting close problem.

scholarly journals Laboratory experimental investigation of heat transport in fractured media

2016 ◽  
Author(s):  
Claudia Cherubini ◽  
Nicola Pastore ◽  
Concetta I. Giasi ◽  
Nicoletta Maria Allegretti
Keyword(s):  
Heat Transport ◽  
Power Plants ◽  
Time Moment ◽  
Experimental Studies ◽  
Renewable Resource ◽  
Fractured Media ◽  
Single Fracture ◽  
Tracer Transport ◽  
Transport Dynamics ◽  
Experimental Apparatus

Abstract. Low enthalpy geothermal energy is a renewable resource that is still underexploited nowadays, in relation to its potential for development in the society worldwide. Most of its applicabilities have already been investigated, such as: heating and cooling of private and public buildings, roads defrost, cooling of industrial processes, food drying systems, desalination. One of the major limitations related to the choice of installing low enthalpy geothermal power plants regards the initial investment costs. In order to increase the optimal efficiency of installations which use groundwater as geothermal resource, flow and heat transport dynamics in aquifers need to be well characterized. Especially in fractured rock aquifers these processes represent critical elements that are not well known. Therefore there is a tendency to oversize geothermal plants. In literature there are very few studies on heat transport especially in fractured media. This study is aimed to deepen the understanding of this topic through heat transport experiments in fractured network and their interpretation. The heat transfer tests have been carried out on the experimental apparatus previously employed to perform flow and tracer transport experiments, which has been modified in order to analyze heat transport dynamics in a network of fractures. In order to model the obtained thermal breakthrough curves, the Explicit Network Model (ENM) has been used, which is based on an adaptation of a Tang's solution for the transport of the solutes in a semi-infinite single fracture embedded in a porous matrix. Parameter estimation, time moment analysis, tailing character and other dimensionless parameters have permitted to better understand the dynamics of heat transport and the efficiency of heat exchange between the fractures and matrix. The results have been compared with the previous experimental studies on solute transport.

scholarly journals “Ian Schneider”

2016 ◽  
Vol 5 (4) ◽  
pp. 4-5 ◽  
Author(s):  
Jonathan Wyatt
Keyword(s):  
Time Moment

A poetic emergence of the particular—a particular place, day, time, moment, event—and its (extra)ordinary affect.

Fast real-time moment-ratio analysis of multibreath nitrogen washout in children

1985 ◽  
Vol 59 (4) ◽  
pp. 1137-1144 ◽  
Author(s):  
R. Kraemer ◽  
B. Meister
Keyword(s):  
Real Time ◽  
Time Moment ◽  
Digital Processing ◽  
Ratio Analysis ◽  
Delay Compensation ◽  
Ventilation Inhomogeneity ◽  
Moment Ratio ◽  
Residual Capacity ◽  
The Moment ◽  
Washout Curves

To apply real-time moment-ratio analysis to multibreath N2-washout curves (MBNW) from children, a new processor-controlled device was constructed. Flow and fractional N2 concentration (FN2) were each sampled by 200 Hz. An electromagnetic triple-valve system, with an instrumental dead space of 36 ml and a valve resistance of 0.3 cmH2O . l-1 . s, was connected in series with a pneumotachograph and an N2 analyzer (Ohio 720) placed next to the mouthpiece. A FORTRAN/MACRO program on a PDP 11/23 computer enabled measurement of inspiratory and expiratory flow and FN2 sampling by a 12-bit analog-to-digital converter. The fast real-time digital processing of the N2 and flow signals incorporated filtering, delay compensation, and corrections for the effects of changes in gas composition and temperature. MBNW dynamics of the lungs were studied in 17 healthy and 28 asthmatic children and in 16 patients with cystic fibrosis, evaluating the moment ratios of the washout curves as indices of the ventilation characteristics. Intrasubject variability of the moment ratios (m1/m0, m2/m0) and determination of functional residual capacity (FRC) varied between 6.3 and 14.7% (depending on which parameter is considered) and was comparatively lower than other indices previously investigated in adults. In addition, the sensitivity of the moment ratios for discriminating different stages of ventilation inhomogeneity was superior to other indices. m2/m0 is closely related to the simultaneously measured airway resistance, and the ratio between cumulative expired volume and FRC is correlated with the ratio between residual volume and total lung capacity.

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