Review of Global Simulation Studies of Effect of Ionospheric Outflow on Magnetosphere-Ionosphere System Dynamics

This paper presents an approach for modeling powder delivery system dynamics in low flow rate applications. Discrete particle modeling (DPM) is utilized to analyze the motion of individual powder particles. In DPM, an irregular bouncing model is employed to represent the powder dispersion in the powder delivery system induced by non-spherical particle-wall collisions. A three-dimensional friction collision model is utilized to simulate the interactions between particles and the powder delivery system walls. The modeling approach is experimentally verified and simulation studies are conducted to explore the effect of powder delivery system mechanical design parameters (i.e., tube length, diameter, and angle, number of tubes and meshes, and mesh orientation and size) on the powder flow dynamics. The simulation studies demonstrate that the powder delivery system dynamics can be modeled by a pure transport delay coupled with a first order system.

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Constrained Quasi-Spectral MPSP With Application to High-Precision Missile Guidance With Path Constraints

Journal of Dynamic Systems Measurement and Control ◽

10.1115/1.4048488 ◽

2020 ◽

Vol 143 (3) ◽

Author(s):

Sabyasachi Mondal ◽

Radhakant Padhi

Keyword(s):

System Dynamics ◽

High Precision ◽

High Speed ◽

Lateral Acceleration ◽

Practical Significance ◽

Simulation Studies ◽

Missile Guidance ◽

Computationally Efficient ◽

Control Variables ◽

Path Constraints

Abstract This paper extends the recently developed quasi-spectral model predictive static programming (QS-MPSP) to include state and control path-constraints and yet retain its computational efficiency. This is achieved by (i) formulating the entire problem in the control variables alone by (a) converting the system dynamics to an equivalent algebraic constraint and (b) converting the state constraints to equivalent control constraints, both of which is done by manipulating the system dynamics, (ii) representing the control variables in Quasi-spectral form, which makes the number of free-variables independent of time-grids and (iii) using a computationally efficient optimization algorithm to solve this low-dimensional problem. This generic computationally efficient technique is utilized next as an effective lead angle, and lateral acceleration constrained optimal missile guidance to intercept incoming high-speed ballistic targets with high precision successfully. Both of these constraints, as well as near-zero miss-distance, are of high practical significance for this challenging problem. Extensive three-dimensional simulation studies show the effectiveness of the newly proposed constrained QS-MPSP guidance algorithm. Six degrees-of-freedom simulation studies have also been carried out using autopilot in the loop to validate the results more realistically.

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Simulation of multi-echelon supply chain inventory transshipment models at different levels

SIMULATION ◽

10.1177/0037549717698034 ◽

2017 ◽

Vol 94 (7) ◽

pp. 563-575 ◽

Cited By ~ 1

Author(s):

Bo Yan ◽

Lifeng Liu

Keyword(s):

Supply Chain ◽

Customer Satisfaction ◽

System Dynamics ◽

Simulation Studies ◽

Customer Requirement ◽

Stock Level ◽

Satisfaction Rate ◽

The Stability ◽

Different Levels ◽

Dynamics Method

An inventory transshipment model comprising manufacturers, distributors, and retailers based on multi-echelon supply chains is established using the system dynamics method. Thereafter, the single-, double-, three-, and four-chain inventory transshipment models at different levels are comparatively analyzed through simulation. Studies indicated that from the single- to four-chain inventory transshipment models, the average stock level minimally changed and declined. Meanwhile, the stability of the supply chain inventory improved continuously. The average customer requirement satisfaction rate of the inventory transshipment system consistently increases as the number of chains added to the transshipment system increases. However, the growth range of the average customer satisfaction rate continuously decreases with the increasing transshipment costs.

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Non-smooth models and simulation studies of the suspension system dynamics basing on piecewise linear luz(…) and tar(…) projections

Applied Mathematical Modelling ◽

10.1016/j.apm.2021.01.039 ◽

2021 ◽

Vol 94 ◽

pp. 619-634

Author(s):

Dariusz Żardecki ◽

Andrzej Dębowski

Keyword(s):

System Dynamics ◽

Piecewise Linear ◽

Suspension System ◽

Simulation Studies

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Benefits from Computerized Adaptive Testing as Seen in Simulation Studies

European Journal of Psychological Assessment ◽

10.1027//1015-5759.15.2.91 ◽

1999 ◽

Vol 15 (2) ◽

pp. 91-98 ◽

Cited By ~ 10

Author(s):

Lutz F. Hornke

Keyword(s):

Measurement Error ◽

Computerized Adaptive Testing ◽

Test Procedure ◽

Adaptive Testing ◽

Parameter Estimates ◽

Simulation Studies ◽

Computerized Adaptive Test ◽

Item Banks ◽

Item Parameters ◽

General Reliability

Summary: Item parameters for several hundreds of items were estimated based on empirical data from several thousands of subjects. The logistic one-parameter (1PL) and two-parameter (2PL) model estimates were evaluated. However, model fit showed that only a subset of items complied sufficiently, so that the remaining ones were assembled in well-fitting item banks. In several simulation studies 5000 simulated responses were generated in accordance with a computerized adaptive test procedure along with person parameters. A general reliability of .80 or a standard error of measurement of .44 was used as a stopping rule to end CAT testing. We also recorded how often each item was used by all simulees. Person-parameter estimates based on CAT correlated higher than .90 with true values simulated. For all 1PL fitting item banks most simulees used more than 20 items but less than 30 items to reach the pre-set level of measurement error. However, testing based on item banks that complied to the 2PL revealed that, on average, only 10 items were sufficient to end testing at the same measurement error level. Both clearly demonstrate the precision and economy of computerized adaptive testing. Empirical evaluations from everyday uses will show whether these trends will hold up in practice. If so, CAT will become possible and reasonable with some 150 well-calibrated 2PL items.

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