Bounds in Tree-Based Approaches to Generate Project Portfolios in the Presence of Interactions

2021 ◽  
Vol 13 (4) ◽  
pp. 50-70
Author(s):  
Rudolf vetschera ◽  
Jonatas Araùjo de Almeida
Keyword(s):  
Decision Analysis ◽  
Computational Study ◽  
Decision Models ◽  
Search Process ◽  
Combinatorial Explosion ◽  
Approximation Quality ◽  
Portfolio Decision ◽  
Project Portfolios ◽  
Important Branch

Portfolio decision models have become an important branch of decision analysis. Portfolio problems are inherently complex, because of the combinatorial explosion in the number of portfolios that can be constructed even from a small number of items. To efficiently construct a set of portfolios that provide good performance in multiple criteria, methods that guide the search process are needed. Such methods require the calculation of bounds to estimate the performance of portfolios that can be obtained from a given partial portfolio. The calculation of such bounds is particularly difficult if interactions between items in the portfolio are possible. In the paper, the authors introduce a method to represent such interactions and develop various bounds that can be used in the presence of interactions. These methods are then tested in a computational study, where they show that the bounds they propose frequently provide a good approximation of actual outcomes, and also analyze specific properties of the problem that influence the approximation quality of the proposed bounds.

A Comprehensive Computational Study on OCH+-Rg (Rg = He, Ne, Ar, Kr, Xe) Complexes

2003 ◽  
Vol 68 (3) ◽  
pp. 489-508 ◽  
Author(s):  
Yinghong Sheng ◽  
Jerzy Leszczynski
Keyword(s):  
Computational Study ◽  
Relativistic Effects ◽  
Dft Method ◽  
Basis Set ◽  
Rare Gas ◽  
Geometrical Parameters ◽  
Minor Effect ◽  
Dissociation Energies ◽  
Equilibrium Geometries

The equilibrium geometries, harmonic vibrational frenquencies, and the dissociation energies of the OCH+-Rg (Rg = He, Ne, Ar, Kr, and Xe) complexes were calculated at the DFT, MP2, MP4, CCSD, and CCSD(T) levels of theory. In the lighter OCH+-Rg (Rg = He, Ne, Ar) rare gas complexes, the DFT and MP4 methods tend to produce longer Rg-H+ distance than the CCSD(T) level value, and the CCSD-calculated Rg-H+ bond lengths are slightly shorter. DFT method is not reliable to study weak interaction in the OCH+-He and OCH+-Ne complexes. A qualitative result can be obtained for OCH+-Ar complex by using the DFT method; however, a higher-level method using a larger basis set is required for the quantitative predictions. For heavier atom (Kr, Xe)-containing complexes, only the CCSD method predicted longer Rg-H+ distance than that obtained at the CCSD(T) level. The DFT method can be applied to obtain the semiquantitative results. The relativistic effects are expected to have minor effect on the geometrical parameters, the H+-C stretching mode, and the dissociation energy. However, the dissociation energies are sensitive to the quality of the basis set. The nature of interaction between the OCH+ ion and Rg atoms was also analyzed in terms of the interaction energy components.

scholarly journals The Prisoners’ Dilemma in collaborative carriers’ request selection

2021 ◽  
Vol 29 (1) ◽  
pp. 73-87 ◽  
Author(s):  
Margaretha Gansterer ◽  
Richard F. Hartl
Keyword(s):  
Computational Study ◽  
Logistics Industry ◽  
Individual Outcomes ◽  
Selection Strategies ◽  
Prisoners Dilemma ◽  
Trading Mechanisms ◽  
And Behavior ◽  
The Impact ◽  
Idle Capacity

AbstractLogistics providers have to utilize available capacities efficiently in order to cope with increasing competition and desired quality of service. One possibility to reduce idle capacity is to build coalitions with other players on the market. While the willingness to enter such coalitions does exist in the logistics industry, the success of collaborations strongly depends on mutual trust and behavior of participants. Hence, a proper mechanism design, where carriers do not have incentives to deviate from jointly established rules, is needed. We propose to use a combinatorial auction system, for which several properties are already well researched but little is known about the auction’s first phase, where carriers have to decide on the set of requests offered to the auction. Profitable selection strategies, aiming at maximization of total collaboration gains, do exist. However, the impact on individual outcomes, if one or more players deviate from jointly agreed selection rules is yet to be researched. We analyze whether participants in an auction-based transport collaboration face a Prisoners’ Dilemma. While it is possible to construct such a setting, our computational study reveals that carriers do not profit from declining the cooperative strategy. This is an important and insightful finding, since it further strengthens the practical applicability of auction-based trading mechanisms in collaborative transportation.

scholarly journals A Novel Dissipativity-Based Control for Inexact Nonlinearity Cancellation Problems

2015 ◽  
Vol 2015 ◽  
pp. 1-13 ◽  
Author(s):  
Giacomo Innocenti ◽  
Paolo Paoletti
Keyword(s):  
Control Strategy ◽  
Feedback Loop ◽  
Controller Design ◽  
Natural Control ◽  
Standard Methods ◽  
Approximation Quality ◽  
Linear Controller ◽  
Benchmark System ◽  
Global Linearization

When dealing with linear systems feedback interconnected with memoryless nonlinearities, a natural control strategy is making the overall dynamics linear at first and then designing a linear controller for the remaining linear dynamics. By canceling the original nonlinearity via a first feedback loop, global linearization can be achieved. However, when the controller is not capable of exactly canceling the nonlinearity, such control strategy may provide unsatisfactory performance or even induce instability. Here, the interplay between accuracy of nonlinearity approximation, quality of state estimation, and robustness of linear controller is investigated and explicit conditions for stability are derived. An alternative controller design based on such conditions is proposed and its effectiveness is compared with standard methods on a benchmark system.

Parametric computational study of particle trajectory deviation probabilistic nature influencing the unevenness of their localization in the model tract

2021 ◽  
Author(s):  
A.V. Voronetskiy ◽  
K.Yu. Arefiev ◽  
M.A. Abramov
Keyword(s):  
Computational Study ◽  
Circular Cross Section ◽  
Cylindrical Part ◽  
Two Phase ◽  
Dispersed Particles ◽  
Alloy Particles ◽  
Model Channel ◽  
Probabilistic Nature ◽  
Number Of Particles

The purpose of this research was to investigate the spatial structure of a two-phase flow in a supersonic model channel of circular cross-section with a diameter of the cylindrical part of ~10 mm. For modeling, we used the Euler-Lagrange approach in combination with a probabilistic estimate of the dispersed particles deviation from their base trajectory. Chromium-nickel alloy particles with a diameter of 15 to 40 μm move in the channel in a special way, which was considered in the paper. Furthermore, we analyzed how the nature of the distribution function of the particle’s root-mean-square deviation from its base trajectory influences the quality of mixing of the dispersed phase with the flow and the number of particles interacting with the walls of the flow path.

Grid Quality Measures for PEBI Grids

2021 ◽  
Author(s):  
Ilya Mishev ◽  
Ruslan Rin
Keyword(s):  
Flow Behavior ◽  
Quality Measures ◽  
Approximation Properties ◽  
Approximation Quality ◽  
Flux Approximation ◽  
The Matrix ◽  
Eventual Loss ◽  
Dynamic Measures ◽  
The Impact

Abstract Combining the Perpendicular Bisector (PEBI) grids with the Two Point Flux Approximation (TPFA) scheme demonstrates a potential to accurately model on unstructured grids, conforming to the geological and engineering features of real grids. However, with the increased complexity and resolution of the grids, the PEBI conditions will inevitably be violated in some cells and the approximation properties will be compromised. The objective is to develop accurate and practical grid quality measures that quantify such errors. We critically evaluated the existing grid quality measures and found them lacking predictive power in several areas. The available k-orthogonality measures predict error for flow along the strata, although TPFA provides an accurate approximation. The false-positive results are not only misleading but can overwhelm further analysis. We developed the so-called "truncation error" grid measure which is probably the most accurate measure for flow through a plane face and accurately measures the error along the strata. We also quantified the error due to the face curvature. Curved faces are bound to exist in any real grid. The impact of the quality of the 2-D Delaunay triangulation on TPFA approximation properties is usually not taken into account. We investigate the impact of the size of the smallest angles that can cause considerable increase of the condition number of the matrix and an eventual loss of accuracy, demonstrated with simple examples. Based on the analysis, we provide recommendations. We also show how the size of the largest angles impacts the approximation quality of TPFA. Furthermore, we discuss the impact of the change of the permeability on the TPFA approximation. Finally, we present simple tools that reservoir engineers can use to incorporate the above-mentioned grid quality measures into a workflow. The grid quality measures discussed up to now are static. We also sketch the further extension to dynamic measures, that is, how the static measures can be used to detect change in the flow behavior, potentially leading to increased error. We investigate a comprehensive set of methods, several of them new, to measure the static grid quality of TPFA on PEBI grids and possible extension to dynamic measures. All measures can be easily implemented in production reservoir simulators and examined using the suggested tools in a workflow.

Development and research of a genetic method for the analysis and determination of the location of power grid objects

2020 ◽  
Vol 25 (1) ◽  
pp. 20-42
Author(s):  
Fedorchenko I. ◽  
◽  
Oliinyk A. ◽  
Korniienko S. ◽  
Kharchenko A. ◽  
...  
Keyword(s):  
Power Supply ◽  
Narrow Range ◽  
Search Space ◽  
Distribution Networks ◽  
Power Supplies ◽  
Search Process ◽  
Stable Convergence ◽  
Genetic Method

The problem of combinatorial optimization is considered in relation to the choice of the location of the location of power supplies when solving the problem of the development of urban distribution networks of power supply. Two methods have been developed for placing power supplies and assigning consumers to them to solve this problem. The first developed method consists in placing power supplies of the same standard sizes, and the second - of different standard sizes. The fundamental difference between the created methods and the existing ones is that the proposed methods take into account all the material of the problem and have specialized methods for coding possible solutions, modified operators of crossing and selection. The proposed methods effectively solve the problem of low inheritance, topological unfeasibility of the found solutions, as a result of which the execution time is significantly reduced and the accuracy of calculations is increased. In the developed methods, the lack of taking into account the restrictions on the placement of new power supplies is realized, which made it possible to solve the problem of applying the methods for a narrow range of problems. A comparative analysis of the results obtained by placing power supplies of the same standard sizes and known methods was carried out, and it was found that the developed method works faster than the known methods. It is shown that the proposed approach ensures stable convergence of the search process by an acceptable number of steps without artificial limitation of the search space and the use of additional expert information on the feasibility of possible solutions. The results obtained allow us to propose effective methods to improve the quality of decisions made on the choice of the location of power supply facilities in the design of urban electrical.

Application of Multiple Criteria Decision Analysis and Optimisation Methods in Evaluation of Quality of Learning Objects

2013 ◽  
pp. 136-150
Author(s):  
Eugenijus Kurilovas ◽  
Irina Vinogradova ◽  
Silvija Serikoviene
Keyword(s):  
Decision Analysis ◽  
Quality Criteria ◽  
Learning Objects ◽  
Scientific Models ◽  
Expert Evaluation ◽  
Quality Of Learning ◽  
Technological Quality ◽  
Optimisation Methods ◽  
Quality Optimisation

This paper analyses and presents the new scientific models and methods for the expert evaluation of quality of learning objects (LOs) paying special attention to LOs reusability level. Currently all existing approaches in the area are quite subjective and depend only on the experience of the decision-makers. The authors analyse several scientific methods and principles to minimise the subjectivity level in the expert evaluation of LOs quality. They are: (a) the principles of multi-criteria decision analysis for identification of quality criteria, (b) technological quality criteria classification principle, (c) fuzzy group decision making theory to obtain evaluation measures, (d) normalisation of the weights of criteria, and (e) scalarisation method for LOs quality optimisation. The authors demonstrate that the complex application of these approaches could significantly improve the quality of the expert evaluation of LOs and noticeably reduce the level of the expert evaluation subjectivity. The paper also presents the example of practical application of these approaches for evaluation of LOs for Mathematics subject.

Bridging Modernity by Improving Informal Sector for Substantially Industrialized Construction in Developing Countries

2018 ◽  
pp. 1706-1735
Keyword(s):  
Developing Countries ◽  
Human Resources ◽  
Construction Industry ◽  
Informal Sector ◽  
Cost Management ◽  
Labor Cost ◽  
Decision Models ◽  
Improve Performance ◽  
Construction Productivity

We have argued in Chapters 1-3 that the construction industry in developing countries is dominated by the strong presence of SMEs and “jobbers”. The informal sector workers constitute the essential provider of human resources construction industry. So far, the weaknesses of the construction industry in developing countries have been identified. As a result, various decision models were proposed for largely improving labor cost management and scheduling (time) with the aim of improving productivity. In a single volume like this, it is unrealistic to cover all aspects to improve performance. This chapter will now provide ideas on how quality of projects can also be improved so as to maintain a balance between cost, time and quality. Furthermore, the management of onsite workshops that can lead to construction productivity will be examined.

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