The Open Operational Research Journal

Published by Bentham Science Publishers
Online ISSN: 1874-2432
Publications
Article
This study considers a class of two-machine flow-shop scheduling problems with job delivery coordination. Both vehicle capacity and transportation times are also investigated. The objective is to minimize the mean arrival time of jobs. Two integer programming models are developed to optimally solve this problem. These two integer programming models are Models 1 and 2. Model 1 adopts the concept of assignment problem to formulate the proposed problems, while Model 2 bases on the dichotomous constraints models. Model 2 is theoretically better than Model 1 in size complexity analysis.
 
Article
This paper focuses on an optimal disposal mechanism by extending the work of Tripathy et al. (11) to consider the system cost as fuzzy under flexibility and reliability criteria. It has been observed that by using a non-random optimization technique the derived disposal plan may result in no substantial difference in the system cost between the crisp and fuzzy model. Various numerical analyses demonstrate the effectiveness of proposed method. The results of the best order size obtained by the robust study are in general, very satisfactory. Finally through numerical examples sensitivity analysis show the influence of key model parameters. Based on consistency study, fuzzy strategy is better off than that of fixed cost strategy. Through sensitivity and robust analysis the results indicate that the performance of the proposed approach is superior to that of its crisp model. AMS (2000) Subject classification No: 90B05.
 
Article
We present the mean value cross decomposition algorithm and its simple enhancement for the two-stage stochastic linear programming problem with complete recourse. The mean value cross decomposition algorithm employs the Benders (primal) subproblems as in the so-called "L-shaped" method but eliminates the Benders master problem for generating the next trial first-stage solution, relying instead upon Lagrangian (dual) subproblems. The Lagrangian multipliers used in defining the dual subproblems are in turn obtained from the primal subproblems. The primal subproblem separates into subproblems, one for each scenario, each containing only the second-stage variables. The dual subproblem also separates into subproblems, one for each scenario which contains both first- and second-stage variables, and additionally a subproblem containing only the first-stage variables. We then show that the substantial computational savings may be obtained by solving at most iterations only the dual subproblem with the first-stage variables and bypassing the termination test. Computational results are highly encouraging.
 
Article
Protracted voters' waiting time is widely accepted to be a major impediment to voters' turnout at elections. This paper presents a queueing simulation-optimization based methodology for reducing voter waiting time at the polls. In many places, insufficient ballot materials and poll presiding officials, in combination with lengthy voting time and high voters' traffic, have caused long lines and disenfranchised voters who left without voting. Although the underlying simulation model employs a blend of queueing theory, discrete-event simulation, and optimization, the procedure offers a simplistic methodology, to be used by the typically nontechnical election official, without getting him involved in the intricacies and complexities involved in the modeling process. This paper focuses on methods to mitigate voters' waiting time at the polls and reduce the number of disenfranchised voters. Our simulation results can be used in planning a cost- effective election process that will produce expeditious elections. AMS MSC (2010): 60K25; 68M20; 90B22; 90B15; 37M05; 93C65; 91B12.
 
Article
Sheet-metal parts typically follow a unidirectional flow in the sheet-metal shop. In the first cutting stage, a large sheet is cut to different unfolded parts with a laser cutting machine. To avoid waste material different parts are combined on a sheet. Next, the 2D parts are transformed to 3D products with air bending. In this bending stage, time-consuming set-ups between production layouts are reduced as much as possible. Separate optimisation of cutting and air bending causes the optimisation benefits to counteract one another. Integrated models have been proposed for both single-and multiple-machine classes, but calculation times are too high and avoidable changeovers still occur. In this paper, by applying variable neighbourhood search with a number of different starting solutions, local optima of good quality are determined for minimising the makespan and the total flow time for both the single-machine and the multi-machine classes. Because the two performance measures are important for a good production plan, bicriteria optimisation by means of a simultaneous and a hierarchical approach, is also considered. Compared to the mathematical programming models for the combined cutting and bending operations, both quality and required computation time are improved for several real-life instances.
 
f j /f k Depends on the Magnitudes of y j1 and y k1 with y j1 =y k1 
g j /g k Independent of the Magnitudes of y j1 and y k1 with y j1 =y k1 
Fundamental Properties of Additive and Multiplicative Rules 
Article
Additive and multiplicative aggregations of ratio scale preferences are frequently used in multi-criteria decision making models. In this paper, we compare the advantages and limitations of these two aggregation rules by exploring only their fundamental properties after ratio scaled local priorities and criteria weights have been successfully generated from the decision maker. The comparisons of these properties are therefore independent of ancillary procedures such as interac-tive elicitations from decision makers, pairwise comparisons and calculations of local priorities and criteria weights. We compare six fundamental properties of the two aggregation rules. The criteria weights used in the multiplicative aggrega-tion have complicated meanings which are not well understood and often mixed up in the ambiguous notion of "criteria importance". As the scaling factors of the local preference values do not appear explicitly in the computations of the rela-tive ratios of the overall preferences in the multiplicative aggregation model, the relative ratios remain unchanged when the scaling factors are changed or an alternative is added or deleted. Furthermore, the relative ratios in the multiplicative aggregation do not depend on similar local preference values which cancel each other out mathematically. It is quite evi-dent that the additive aggregation model is superior and easier for decision makers to use and understand. We recommend the additive aggregation rule over the multiplicative aggregation rule.
 
Comparison of the Problem-Specific Heuristics for the 143 Test Instances
Article
In this paper we consider approximation of the Capacitated Arc Routing Problem, which is the problem of servicing a set of edges in a graph using a fleet of capacity constrained vehicles. We present a 7 3 2 W approximation algorithm for the problem and prove that this algorithm outperforms the only existing approximation algorithm for the problem. Furthermore , we give computational results showing that the new algorithm performs very well in practice.
 
Article
Low population density and large distance from civilization centers generate high costs of isolation. Immigra- tion reduces these costs for veteran residents but reduces social and cultural cohesion, increases the demand for scarce re- sources and affects the rate of urban unemployment. An expected net benefit maximization model for determining the op- timal population size and the equilibrium urban-rural composition of an island similar to Australia is constructed. The model is simulated for various agricultural water prices. The simulation results illustrate the central role of the effect of immigration on urban unemployment rate in the determination of the island's optimal population size.
 
Article
We propose several new models for separate and spatially distributed auction based markets where partici- pants' reactions are described by general price mappings and show that they admit equivalent variational inequality for- mulations. This approach is utilized for the derivation of existence and uniqueness results and for construction of efficient solution methods.
 
Estimation of r x 0 ( ) using the posterior distribution.  
Article
In this article, we propose a theoretical framework to estimate performance measures in simulation experiments , incorporating both sample data from a random component and priors on input parameters of the simulation model. Our approach takes into account both the inherent uncertainty of the model as well as parameter uncertainty. We discuss the estimation of a conditional expectation under a Bayesian framework and point and variability estimators are proposed when direct sampling from the posterior distribution is not allowed. The application and properties of the proposed methodology are illustrated through an inventory model and simulation experiments using a Markovian model.
 
Log of the Spanish stock market prices.
Article
It is well known that the Spanish stock market index (IBEX 35) exhibits unit roots. However, the implications of possible structural breaks in this series have not been deeply investigated. In this paper, we show that, when including a break at the beginning of 1998, the order of integration of the series becomes slightly smaller, strengthening the evidence of mean-reverting behaviour. When the break date is supposed to be unknown, it is found to be January 1998, with both subsamples still being characterised by a high degree of persistence.
 
Article
The bullwhip effect refers to the phenomenon of demand distortion in a supply chain. By eliminating or con-trolling this effect, it is possible to increase product profitability. The main focus of this work is to apply a control tech-nique, based on the divergence of system, to reduce the bullwhip effect in a single-product one echelon supply chain, in which an Order-Up-To (OUT) order policy is applied. First the relationships between bullwhip, stability of the supply chain and the total costs are analyzed. Second the divergence-based control strategy is applied to stabilize the supply chain dynamics with a considerable reduction of the total costs (> 30%) and, in relevant cases, of the bullwhip effect.
 
Article
This paper considers a general 0-1 random fuzzy programming problem including some previous 0-1 stochastic and fuzzy programming problems. The proposal problem is not a well-defined problem due to including random fuzzy variables. Therefore, by introducing chance constraint and fuzzy goal for objective function and considering the maximi-zation for the degrees of possibility that the objective function value satisfies the fuzzy goal, main problem is transformed into a deterministic equivalent problem. Furthermore, by using the assumption that each random variable is distributed ac-cording to a normal distribution, the problem is equivalently transformed into a basic 0-1 programming problem, and the efficient strict solution method to find an optimal solution is constructed.
 
below shows first few iterations of the Excel implementation of the above problem. 
Article
In recent years the introduction and development of Interior-Point Methods has had a profound impact on optimization theory as well as practice, influencing the field of Operations Research and related areas. Development of these methods has quickly led to the design of new and efficient optimization codes particularly for Linear Programming. Consequently, there has been an increasing need to introduce theory and methods of this new area in optimization into the appropriate undergraduate and first year graduate courses such as introductory Operations Research and/or Linear Programming courses, Industrial Engineering courses and Math Modeling courses. The objective of this paper is to discuss the ways of simplifying the introduction of Interior-Point Methods for students who have various backgrounds or who are not necessarily mathematics majors.
 
Article
The research studies the internationalization process model developed by Johanson and Vahlne and derives integer programming investment decision model that consider the risk attitudes of investment firms. Johanson and Vahlne's model provides a starting point for building a model that suits the investment approach and decision making process. The revised integer programming models helps firms manage the risks of their investments and derive accurate investment strategies based on investment objectives and constraints. This research also performs the sensitivity analysis of the revised international investment decision model.
 
Trends in use of short-acting and long-acting methods among routine contraceptive acceptors by year, Southern Nations, Nationalities, and Peoples' Region, Ethiopia, fiscal year (FY) 2010-17 (N=864,303).
Trends in use of short-acting and long-acting methods among post-abortion contraceptive acceptors by year, Southern Nations, Nationalities, and Peoples' Region, Ethiopia, fiscal year (FY) 2010-17 (N=54,773).
Trends in the method mix among routine contraceptive acceptors by year, Southern Nations, Nationalities, and Peoples' Region, Ethiopia, fiscal year (FY) 2010-17, (N=864,303). *Values for tubal ligation were 0% in 2010, 2011 and 2012; 0.1% in 2013, 2014 and 2015; 0.07% in 2016 ; and 0.05 in 2017. IUDs, intrauterine devices; OCPs, oral contraceptive pills.
Trends in the Method Mix Among Post-abortion Contraception Acceptors by Year, Southern Nations, Nationalities, and Peoples' Region, Ethiopia, fiscal year (FY) 2010-17, (N=54,773). *Values for tubal ligation were 0% in 2010, 2011 and 2012; 0.03% in 2013; 0.2 in 2014 ; 0.05 in 2015; and 0% % in 2016 and 2017. IUDs, intrauterine devices; OCPs, oral contraceptive pills.
Article
In Ethiopia, a low contraceptive prevalence and high unmet Background: need coupled with skewed method mix clearly signify the need for comprehensive family planning delivery strategies. Ipas implemented problem-focused intervention to improve service delivery standards and provide accessible, high-quality family planning services. This analysis seeks to compare the contraceptive method mix in routine and post-abortion contraception services and to suggest how multifaceted service delivery approaches can help address the unmet family planning need. The intervention was implemented in 127 public health facilities Methods: providing both routine and post-abortion contraception services, from 2010 to 2017. The intervention focused on service delivery and program management gaps identified during the baseline assessment. Service data regularly collected from intervention facilities and entered into a Microsoft Excel database to conduct descriptive analysis, review trends, and monitor progress. Trend analysis of method choice patterns revealed that the share Results: of method mix for long-acting reversible contraceptives(LARCs) rose from 3% in 2010 to 40% in 2017 in routine family planning service, whereas in the post-abortion contraception service, the share for LARCs climbed from 2% in 2010 to 62% in 2017(P<0.001). Trend analysis of LARC uptake in post-abortion contraception revealed that implant use rose from 2% in 2010 to 54% in 2017, while intrauterine device (IUD) use increased from 0.1% in 2010 to 9% in 2017. In routine program, proportion of implant acceptors increased from 3% in 2010 to 35% in 2017, while IUD acceptance increased far more slowly, from only 0.07% to 5% over the same period. Comprehensive contraceptive service delivery strategies, Conclusions: such as integration of family planning with other maternal health services can help the service to reach clients with a variety of needs, a key factor for a higher uptake of LARCs by abortion clients as compared to routine family planning program.
 
Explaining the concept of System Dynamics within System Thinking 13 .
SD Electricity Planning-Low Carbon Development Model (adapted from Momodu et al. 4 Op cost: operational cost, Tx cost: Tax cost, MW* capacity, GWh**: power demand, GDP: gross domestic product. *MW = Megawatts, **GWh = gigawatt hours.
Causal-Loop Diagram of the NEPS adopted for WAPP System 24 .
Article
Background : It is imperative to develop an efficient strategic approach to managing the push-pull factor in economic development, particularly as relates to climate change and energy interactions in the West African Region. This article demonstrates the use of System Dynamics Modelling (SDM) for that purpose; to manage the development of energy growth with reduced impact in regards to climate change. The complexities of energy planning in relation to climate change necessitates the need for the tool to examine low carbon economy mixed with traditional approaches of planning. Methods : Vensim DSS version 6.2 was used to develop the model. WAPP member country level data elicited from WAPP and ECOWAS Regional Electricity Regulatory Authority (ERERA) serves as the set of basic data used to develop and run the main model. These were complemented with other data elicited from various journal articles and internet sources. These include population and its average growth rate, GDP, per capita income, average per capita electricity demand, electricity generated, average electricity tariff, generation technology type, amongst others. Results : SDM demonstrates the capability to understand the theoretical frame for trade-offs between economic development and climate change, by handling the nonlinear relationship between generation adequacy and greenhouse gas (GHG) emission reduction for better targeted strategic regional intervention on climate change. Conclusion : The primary goal of this paper was to demonstrate the use of SDM to aid in resource planning in an inexpensive way to examine low carbon pathway. With the SDM, the goal of low carbon pathway in the energy system was achieved without the cost of controlled trials.
 
Article
Pedestrian’s studies are applied benefit and deployed in many areas; including public trip planning, and human factors analysis for building evacuation, or other situations where masses of people gather such as sporting events, etc. In this paper we describe a simulation system for virtual pedestrians. We mix the concept of fuzzy ant given by Ant Colony paradigm and associated cellular automaton model. We have adopted a fuzzy model for its particular ability to better represent uncertainty and imprecision about space perception. In our model we use it to represent virtual pedestrian’s fuzzy pedestrian’s desirability or visibility. A software solution was developed for this purpose. The Simulation results confirm predictions given by the first-order traffic flow theory. The proposed fuzzification is a preliminary step to consider other factors. The given system in its deployment phase will be integrated for pedestrians’ accidents analysis in urban transportation networks. The strength of our model takes advantage in using explicit Ant Colony model and on projecting fuzzy theory to apprehend pedestrians’ perceptions.
 
Article
The particular structure of the assignment problem made of it a very popular subject of study and an important research tool in operations research and management science. In addition to the importance that the assignment problem represents in its own, it can appear as a relaxation of more complex combinatorial optimization problems. That is why the assignment problem has received great attention from the operations research community. The assignment problem may appear as an optimization problem with multiple objectives. In this paper, we address the problem of efficiency of feasible solutions of a multicriteria assignment problem. It is done in two steps. In the first step, we determine whether or not a given feasible solution of a multicriteria assignment problem is efficient. In a second step, if the feasible solution is not efficient, we provide an efficient solution that dominates it. The proposed method consists of transforming the original problem into an assignment problem with side constraints for which solution techniques already exist.
 
Article
Academic and scientific research often involve the construction of formal and numerical models to solve scientific and engineering problems. Many organizations are evaluating and migrating toward new trends in information systems and IT infrastructure. Now the challenges are less technological and become more cultural as related to governance issues. The paper deals with improving an enterprise's organization by establishing agile and adaptable enterprise system architecture. That not only facilitates new development but also allows for optimizing existing information technology infrastructure to redesign a new enterprise organization structure. For this purpose, we use a canonical approach to implement structural analysis and simplicial complex framework to assess an enterprise's organization. Several methods have been used in this domain like social networks analysis and lattice theory. However Q-analysis method has not been yet exploited in this aim scope. It catches our interest with its topology to capture organizational structure and its strong point that it shows communication inside the same structure. Besides, Q-analysis allows us to diagnose the actual organizational structure of an enterprise and to compare it with the real one. We use different measure indicators like eccentricity, complexity and traffic pattern of a system. A Q-analysis method based on structural analysis and simplicial complexes proves how to ensure synchronization between formal organizational structure and the emergent one, due to perceived changes in business processes. The proposed solution architecture improves organizational structure of an enterprise in order to be more efficient and more aligned with the current processes organization.
 
Cumulative amount of rain fall (mm) into study area during trial periods.
The mean temperature (Temp (Co)) and cumulative precipitation (mm) in to study area during trial years.
The dry matter yield, plant height, tillers per plant and leaf to stem ratio of desho grass varieties under rain fed condition at Jinka Agricul- tural Research Center in South Omo.
The dry matter yield, plant height, tillers per plant and LTSR of desho grass varieties affected by Cropping years at on-station of Jinka Agricultural Research Center in 2017 and 2018 main cropping years.
The year by variety interaction effect on dry matter yield, plant height, tillers per plant and LTSR of desho grass varieties at Jinka Agricul- tural Research Center during 2017 and 2018 main cropping years.
Article
Desho grass is indigenous grass to Ethiopia and belonging to the family of Poaceae and has high biomass production potential. Therefore, this study was initiated to evaluate dry matter yield and chemical composition of four desho (Pennisetum pedicellatum)grass varieties in 2017 and 2018 cropping years at on- station of Jinka Agricultural Research Center under rain fed condition in randomized complete block design with three replications per tested variety. The data on dry matter yield, plant height, tillers per plant, leaf to stem ratio and chemical composition were analyzed using the General Linear Model procedures of SAS. The Areka-DZF#590 gave highest (P>0.001) dry matter yield (27.99t/ha) and whereas the, Kindo kisha-DZF#589 variety gave the lower dry matter yield (14.15t/ha). Likewise, higher (P>0.05) Crude protein (140.12g/Kg, DM) recorded for Areka-DZF#590 and whereas, significantly lowest (P<0.05) Crude protein (90.57g/Kg, DM) obtained for Kindo kasha-DZF#589 variety. Based on this finding, we concluded that farmers who live in comparable agro- ecologies to areas where this stu
 
Article
The Present Study Has Been Conducted To Investigate The Role Of Thymoquinone In Elucidation Of Hepatic Tissue To Overproduce Heat Shock Protein 70 Gene Under Chronic Heat Stress In Mature Male Rats. Ninety Mature Sprague Dewily Male Rats Were Randomly Assigned To Three Equal Groups,Treated For 3 Weeks As Follow: NonStressed Male Rats (Group C) Have Been Kept At Normal Room Temperature (20 ±1Cº) And Daily Supplemented With Distilled Water, Heat-Stressed Male Rats (Groups HS And HSTQ)Have Been Kept At High Room Temperature (35±1Cº) For 6 Hours A Day, And Daily Administered With Distilled Water And TQ Suspension (50 Mg/Kg Bw, Po), Respectively. At The End Of Each Week, 10 Males From Each Group Were Anaesthetized With Thiopental (100 Mg/ Kg, I.P.), Sacrificed And Livers Were Removed. Samples From Hepatic Tissues Have Been Quickly Dipped In DEPC Solution, And Frozen At -80 ºc For Determination Of Hsp70 Gene Expression Levels By SemiQuantitative RT-PCR Analyses.The Results Of Hsp70 Gene Mrna Registered Increased Expression Levels Of Heat Stressed Males (HS And HSTQ Groups) Compared With Control Males At The 2 Abstract nd Week Of Experiment, Which Continued In HSTQ Group At rd The 3 Week Of Experiment, But HS Group Showed Significant Decline To Subnormal Levels That Recorded By Control.In Conclusion It Can Be Proposed That TQ Supplementation Can Be Used As A Potent Therapeutic Agent To Combat Heat Stress.
 
Top-cited authors
Eng Ung Choo
  • Simon Fraser University
William Wedley
  • Simon Fraser University
Sanne Wøhlk
  • Aarhus University
Azedine Boulmakoul
  • Université Hassan II de Casablanca
G. Lesaja
  • Georgia Southern University