Optimization of Multi-Period Rail Procurement Plan

2021 ◽  
pp. 036119812110586
Author(s):  
Hsin-Cheng Shih ◽  
Chih-Heng Yeh ◽  
Yung-Cheng Lai
Keyword(s):  
Sensitivity Analysis ◽  
Asset Management ◽  
Storage Capacity ◽  
Optimization Models ◽  
Scenario Generation ◽  
Generation Process ◽  
Railway Infrastructure ◽  
Procurement Cost ◽  
Metro System ◽  
Procurement Planning

Rail is one of the most expensive assets in railway infrastructure. Therefore, a well-prepared rail procurement plan could benefit the asset management. For the metro system in Taiwan, the rail procurement plan includes two major uncertainties, namely, currency rates and the global steel price. In this study, we propose deterministic and stochastic optimization models using a scenario-generation process to minimize the expected cost of the rail procurement plan. Results from the case studies demonstrate that the proposed models can successfully incorporate the uncertainties and obtain the optimal procurement plan. The sensitivity analysis on budget, storage capacity, and expiration period also provides the metro operator the best strategy to further lower the procurement cost. Adopting these models in rail procurement planning can improve the process and results of rail asset management.

scholarly journals A Multi-Fidelity Model for Simulations and Sensitivity Analysis of Piezoelectric Inkjet Printheads

Micromachines ◽  
2021 ◽  
Vol 12 (9) ◽  
pp. 1038
Author(s):  
Vinh-Tan Nguyen ◽  
Jason Yu Chuan Leong ◽  
Satoshi Watanabe ◽  
Toshimitsu Morooka ◽  
Takayuki Shimizu
Keyword(s):  
Sensitivity Analysis ◽  
Three Dimensional ◽  
Element Model ◽  
Geometrical Parameters ◽  
Generation Process ◽  
Mechanical Coupling ◽  
Design Variables ◽  
Computational Structural Mechanics ◽  
Lumped Element Model ◽  
Inkjet Printhead

The ink drop generation process in piezoelectric droplet-on-demand devices is a complex multiphysics process. A fully resolved simulation of such a system involves a coupled fluid–structure interaction approach employing both computational fluid dynamics (CFD) and computational structural mechanics (CSM) models; thus, it is computationally expensive for engineering design and analysis. In this work, a simplified lumped element model (LEM) is proposed for the simulation of piezoelectric inkjet printheads using the analogy of equivalent electrical circuits. The model’s parameters are computed from three-dimensional fluid and structural simulations, taking into account the detailed geometrical features of the inkjet printhead. Inherently, this multifidelity LEM approach is much faster in simulations of the whole inkjet printhead, while it ably captures fundamental electro-mechanical coupling effects. The approach is validated with experimental data for an existing commercial inkjet printhead with good agreement in droplet speed prediction and frequency responses. The sensitivity analysis of droplet generation conducted for the variation of ink channel geometrical parameters shows the importance of different design variables on the performance of inkjet printheads. It further illustrates the effectiveness of the proposed approach in practical engineering usage.

Railway Infrastructure Asset Management Modelling

2022 ◽  
pp. 209-240
Author(s):  
John Andrews
Keyword(s):  
Complex Systems ◽  
Petri Net ◽  
Asset Management ◽  
Performance Standards ◽  
Service Performance ◽  
Maintenance Strategies ◽  
Maintenance Activity ◽  
Future State ◽  
Railway Infrastructure

Railway infrastructure comprises a large collection of diverse and complex systems and structures. Many of them are aging assets and require a significant budget to deliver the maintenance to ensure the required safety and service performance standards. With such a large amount of money spent each year to maintain and renew the network assets, small percentage savings can amount to substantial sums of money. There is therefore a huge incentive to better understand the degradation that assets experience and how these can be effectively managed through the implementation of efficient maintenance strategies. Track and bridges are the most expensive assets to keep in the required condition, and this chapter provides a method to analyse their degradation and build Petri net models to predict the future state of the asset, the number of each maintenance activity which are expected to be undertaken, and their costs experienced by following a particular strategy. Utilising these models enables the quality of the asset management decisions made to be improved and optimised.

Automated Risk Scenario Generation Using System Functional and Structural Knowledge

2005 ◽  
Author(s):  
Hamed Nejad ◽  
Ali Mosleh
Keyword(s):  
Physical Structure ◽  
Primary Objective ◽  
Structural Knowledge ◽  
Scenario Generation ◽  
Generation Process ◽  
Functional Requirements ◽  
Risk Simulation ◽  
Risk Scenario ◽  
High Level ◽  
Difficult Situations

Simulation may be the most practical way to assess the risk of systems with complex behaviors such as those that include hardware, software and human elements. However, since under normal design conditions human-designed systems generally perform in familiar and expected ways, a typical simulation will frequently lead to known and anticipated results. As such, the simulation program wastes a lot of time on familiar results without generating new knowledge about the system’s vulnerabilities. In order to increase our knowledge of risk, it would be preferable to push the system toward its limits to test the system’s ability to handle more difficult situations. Such an approach can help system designers to better understand risky situations and close the vulnerability gaps in their design. The primary objective of this study is to develop a risk simulation Planner (SimpraPlan) which generates scenarios that can explore the system’s vulnerabilities and offer a superior assessment of the risks involved. The Planner uses high level engineering knowledge (including the functional requirements and physical structure of the system) to generate scenarios that can exploit the system’s vulnerabilities. In this paper, the scenario generation process is explained in detail and scenarios generated by the SimpraPlan are compared with those generated by classical approaches to risk assessment.

Sensitivity Analysis of Hydroelectric Power Generation from Cascading Reservoirs

2012 ◽  
Vol 622-623 ◽  
pp. 1152-1156
Author(s):  
Tilahun Derib Asfaw ◽  
Khamaruzaman Wan Yusof ◽  
Ahmad Mustafa Hashim
Keyword(s):  
Power Generation ◽  
Sensitivity Analysis ◽  
Water Balance ◽  
Storage Capacity ◽  
Reverse Order ◽  
Hydroelectric Power ◽  
Reservoir Storage ◽  
Cascading Reservoirs ◽  
Relationship Of ◽  
Hydroelectric Power Generation

The cascading reservoirs in Perak, Malaysia, were used to test the sensitivity analysis of hydroelectric power generation during refill and deplete period of the reservoirs. The cascading scheme comprises four reservoirs namely Temenggor, Bersia, Kenering and Chenderoh. The test was conducted after the analysis of water balance and stage-storage relationship of each reservoir in the cascading scheme. The result showed that power generation from the smaller reservoir, Bersia, is more sensitive to the change of headrace level, while the larger storage capacity and rated head reservoir is the most sensitive to the change of release. Therefore, to maximize the power generation from the cascading reservoir, the refill operations should be ranked according to the increasing order of the reservoir storage capacity and a reverse order should be followed during deplete period.

scholarly journals Sensitivity of hydrological connectivity in a semiarid basin with a high-density reservoir network

2019 ◽  
Vol 14 (4) ◽  
pp. 1
Author(s):  
Cristian Epifanio Toledo ◽  
Nayra Rodrigues Alcantara
Keyword(s):  
Sensitivity Analysis ◽  
Storage Capacity ◽  
Transmission Loss ◽  
High Density ◽  
The Other ◽  
Hydrological Connectivity ◽  
Runoff Coefficient ◽  
Potential Evaporation ◽  
Hydrographic Basin ◽  
Network Change

Water reservoirs, in general, have been considered to be the major cause of reduction of downstream hydrological connectivity in channels. Therefore, this study analyzed the sensitivity of hydrological connectivity in the Orós Reservoir hydrographic basin by using the ResNet model, designed to simulate the processes involved in fluvial hydrological connectivity in environments with a high density of reservoirs. The analysis of hydrological connectivity was performed with the model ResNetM, which simulated hydrological processes and considered hydrological connectivity between the reservoirs, according to the criteria established in this research. To identify the main elements that affect hydrological connectivity, sensitivity analysis (SI) was performed of some input parameters of the model. The sensitivity analysis indicated that the modification of the topology of the reservoir network was the variable that presented the highest sensitivity to hydrological connectivity, with a sensitivity value of 1.07, followed by the runoff coefficient, which obtained a sensitivity of 0.8. The modification of the rainfall and of the reservoir storage capacity, showed an intermediate sensitivity, with values of 0.46 and 0.45, respectively. On the other hand, the parameters of potential evaporation and transmission loss showed the lowest sensitivity, obtaining values of 0.19 and 0.01, respectively. In conclusion, the runoff coefficient and the reservoir network (change in the reservoir number of the network) were the parameters evaluated with the highest sensitivity of hydrological connectivity. Thus, the alteration of the landscape by man provides significant changes in river navigation between the reservoirs in the basin.

scholarly journals Risk Scenario Generation Based on Importance Measure Analysis

2018 ◽  
Vol 10 (9) ◽  
pp. 3207 ◽  
Author(s):  
Xing Pan ◽  
Lunhu Hu ◽  
Ziling Xin ◽  
Shenghan Zhou ◽  
Yanmei Lin ◽  
...  
Keyword(s):  
Scenario Generation ◽  
Importance Measure ◽  
System Failure ◽  
Generation Process ◽  
Risk Scenarios ◽  
Comparison Results ◽  
Engineering Activity ◽  
Risk Event ◽  
Measure Analysis ◽  
Risk Scenario

A risk scenario is a combination of risk events that may result in system failure. Risk scenario analysis is an important part of system risk assessment and avoidance. In engineering activity-based systems, important risk scenarios are related to important events. Critical activities, meanwhile, mean risk events that may result in system failure. This article proposes these definitions of risk event and risk scenario based on the characteristics of risk in engineering activity-based systems. Under the proposed definitions, a risk scenario framework generated based on importance measure analysis is given, in which critical activities analysis, risk event identification, and risk scenario generation are the three main parts. Important risk events are identified according to activities’ uncertain importance measure and important risk scenarios are generated on the basis of a system’s critical activities analysis. In the risk scenario generation process based on importance analysis, the importance degrees of network activities are ranked to identify the subject of risk events, so that risk scenarios can be combined and generated by risk events and the importance of scenarios is analyzed. Critical activities are analyzed by Taguchi tolerance design, mathematical analysis, and Monte Carlo simulation methods. Then the degrees of uncertain importance measure of activities are solved by the three methods and these results are compared. The comparison results in the example show that the proposed method of uncertain importance measure is very effective for distinguishing the importance level of activities in systems. The calculation and simulation results also verify that the risk events composed of critical activities can generate risk scenarios.

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