Stochastic Optimization by Simulation: Numerical Experiments with M/M/1 Queue in Steady-State

1993 ◽  
Author(s):  
Peter W. Glynn ◽  
Nataly Giroux ◽  
Pierre L'Ecuyer
Keyword(s):  
Steady State ◽  
Stochastic Optimization ◽  
Numerical Experiments

Stochastic Optimization by Simulation: Numerical Experiments with the M/M/1 Queue in Steady-State

1994 ◽  
Vol 40 (10) ◽  
pp. 1245-1261 ◽  
Author(s):  
Pierre L'Ecuyer ◽  
Nataly Giroux ◽  
Peter W. Glynn
Keyword(s):  
Steady State ◽  
Stochastic Optimization ◽  
Numerical Experiments

Numerical Experiments of Coolant Mixing in a Lower Plenum of PWR Under Asymmetric Thermal- Hydraulics Conditions

2006 ◽  
Author(s):  
Masanori Ohtani ◽  
Akito Kozuru ◽  
Yasuyuki Kashimoto ◽  
Mitsuto Montani ◽  
Koutaro Takeda ◽  
...  
Keyword(s):  
Steady State ◽  
Temperature Distribution ◽  
Turbulent Mixing ◽  
Numerical Experiments ◽  
Time Dependent ◽  
Inlet Temperature ◽  
Velocity Fluctuations ◽  
The Core ◽  
State Calculation ◽  
Lower Temperature

Asymmetric thermal-hydraulic conditions among primary loops during a postulated steam line break (SLB) induce a non-uniform temperature distribution at a core inlet. When coolant of lower temperature intrudes into a part of core, it leads to a reactivity insertion and a local power increase. Therefore, an appropriate model for the core inlet temperature distribution is required for a realistic SLB analysis. In this study, numerical experiments were conducted to examine the core inlet temperature distribution under the asymmetric thermal-hydraulic coolant conditions among primary loops. 3D steady-state calculations were carried out for Japanese standard Pressurized Water Reactor (PWR) such as 2, 3, 4 loop types and an advanced PWR. Since the flow in a reactor vessel involves time-dependent velocity fluctuations due to a high Reynolds number condition and a complicated geometry of flow path, the turbulent mixing might be enhanced. Hence, the turbulent thermal diffusivity for the steady-state calculation was examined based on experimental results and another transient calculation. As a result, it was confirmed that (1) the turbulent mixing in a downcomer and a lower plenum were enhanced due to time-dependent velocity fluctuations and therefore the turbulent thermal diffusivity for steady-state calculation was specified to be greater, (2) the core inlet temperature distribution predicted by a steady-state calculation reasonably agreed with a experimental data, (3) the patterns of core inlet temperature distribution were comprehended to be dependent on the plant type, i.e. the number of primary loop and (4) under a low flow rate condition, the coolant of lower temperature appeared on the opposite side of the affected loop due to the effect of a natural convection.

Quenching Vibration on a Harmonically Excited Symmetric Laminated Composite Plate

2021 ◽  
pp. 1-35
Author(s):  
Jiawang Chen ◽  
Philip Cha ◽  
Yichang Shen ◽  
Xiang Zhou
Keyword(s):  
Steady State ◽  
Efficient Method ◽  
Composite Plate ◽  
Numerical Experiments ◽  
Laminated Composite ◽  
Governing Equations ◽  
Laminated Composite Plate ◽  
Constraint Equations ◽  
Damped Oscillators ◽  
Damped Oscillator

Abstract In this paper a simple and efficient method is developed to quench the steady state vibration of a harmonically excited, damped and symmetric laminated composite rectangular plate. This is achieved by enforcing points of zero displacement, or nodes, at some specified locations on the laminated composite plate using properly tuned damped oscillators. Using the assumed-modes method, the governing equations of the laminated composite plate carrying the damped oscillators are first formulated. A set of constraint equations is established by enforcing nodes at user-specified locations on the plate. Two attachment scenarios are considered: when the attachment and node locations coincide, and when they are distinct. Numerical experiments show that for both cases, the damped oscillator parameters can be readily determined and the desired node locations can be successfully imposed. More importantly, enforcing nodes can suppress vibration in the vicinity of the node locations, thereby keeping that region of the laminated composite plate nearly stationary.

The expulsion of magnetic flux by eddies

1966 ◽  
Vol 293 (1434) ◽  
pp. 310-328 ◽  
Keyword(s):  
Magnetic Field ◽  
Steady State ◽  
Magnetic Flux ◽  
Characteristic Time ◽  
Numerical Experiments ◽  
Uniform Magnetic Field ◽  
Conducting Fluid ◽  
Central Field ◽  
The Sun ◽  
Lines Of Force

A convective eddy imposed on an initially uniform magnetic field in a highly conducting fluid distorts the lines of force and amplifies the field. Flux is concentrated outside the eddy; within it, the field grows and its scale of variation decreases until resistive effects become important. Closed lines of force are then formed by reconnexion. The central field decays and a steady state is reached. Within a period, small compared with the characteristic time for resistive decay, magnetic flux is almost entirely expelled from regions of rapid motion and concentrated at the edges of convection cells. This process is demonstrated from numerical experiments. The results are applied to the sun, where the concentrated fields are strong enough to inhibit convection locally.

scholarly journals Queue Size Distribution on a New ND Policy Geo/G/1 Queue and Its Computation Designs

2021 ◽  
Vol 2021 ◽  
pp. 1-16
Author(s):  
Rongxiu Wang
Keyword(s):  
Steady State ◽  
Numerical Experiments ◽  
Probability Generating Function ◽  
Power Saving ◽  
Wireless Sensor ◽  
Size Distributions ◽  
Queue Size ◽  
Improve Model ◽  
Departure Time ◽  
Theoretical Results

This paper examines a new ND policy in the discrete-time Geo/G/1 queue. Under this ND policy, the idle server restarts its service when the N and D policies are simultaneously satisfied. By two classifications of the customers, the probability-generating function and the probabilistic analysis, the steady-state queue size distributions at a departure time and an arbitrary time t + are studied. Finally, the theoretical results are applied to the power-saving problem of a wireless sensor network. To improve model universality and numerical slowness, some computation designs are carried out. Under the N, D, and two ND policies, the numerical experiments are presented to obtain the optimal policy thresholds and the corresponding minimum power consumptions are compared.

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