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Compressing project schedule using activity accelerating and overlapping requires that an intensive time-cost trade-off analysis be carried out, to determine costs and benefits for each day of compression. However, the cost elements and implications of compression techniques differ significantly, since activity accelerating imposes extra direct cost whereas activity overlapping adds a risk of changes and rework. Such a trade-off becomes even more complicated in capital projects comprised of a large number of schedule activities and relationships. The variety of combinations of accelerating and overlapping of different activities in these complex networks can offer numerous possibilities for compression with various costs and potential risks. The lack of a reliable analytical tool for performing a precise cost-benefit analysis causes this critical task to be performed in a subjective manner during the planning stage of projects. The purpose of this paper is to present an advanced method using a multi-objective evolutionary optimization tool seeking the optimum degree of accelerating and overlapping during the schedule compression process. This optimization technique would be beneficial in maximizing project benefits while meeting the intended target dates. Key words: schedule compression, crashing, overlapping, substitution, accelerating, optimization, genetic algorithms. Raccourcir un echeancier de projet par l'acceleration et le chevauchement des activites demande une analyse circonstanciee comparative temps-couts approfondie afin de determiner les couts et les avantages pour chaque jour de compression. Toutefois, les elements de couts et les implications des techniques de compression different beaucoup, puisque l'acceleration des activites exige des couts directs supplementaires alors que le chevauchement des activites ajoute un risque de changements et de reprise du travail. Un tel compromis devient encore plus complique dans les projets d'immobilisations comportant un grand nombre d'activites programmees et de relations. La variete de combinaisons d'acceleration et de chevauchement des differentes activites dans ces reseaux complexes permet d'offrir plusieurs possibilites de compression presentant divers couts et risques potentiels. Le manque d'outils analytiques fiables pour realiser une analyse couts-avantages precise fait que cette tache doit etre realisee subjectivement durant l'etape de planification des projets. Le but de cet article est de presenter une methode evoluee utilisant un outil d'optimisation evolutionnaire a objectifs multiples recherchant le niveau optimal d'acceleration et de chevauchement durant le processus de compression de l'echeancier. Cette technique d'optimisation pourrait permettre de maximiser les avantages d'un projet tout en rencontrant les dates ciblees indiquees. [Traduit par la Redaction] Mots-cles: compression de l'echeancier, compression des delais, chevauchement, substitution, acceleration, optimisation, algorithmes genetiques., Introduction Schedule compression is the technique by which project managers shorten project duration. Generally, schedule compression is performed using two main techniques. The first may be termed 'accelerating'. Accelerating is [...]

Schedule compression is an attempt to reduce project durations for early delivery, or to catch up on occurred delays. This is usually performed using 'crashing', 'overlapping' and 'substitution' of activities. 'Crashing' is shortening task duration by adding more resource hours. 'Substitution' is changing the method or tool by which the activity is performed. 'Overlapping' is performing sequential activities in parallel. Few studies can be found in the literature that compare costs and benefits of each technique and recommend the optimum combination of these techniques in project schedules. In fact, the implications of each technique are inherently different since crashing and substitution impose extra cost whereas overlapping adds the risk of changes and rework. Therefore, it is a challenge to develop a reliable analytical tool for performing time-cost trade- offs using the three methods. There are also few studies in the literature to propose a practical method for performing schedule compression by combining these techniques. The purpose of this paper is to discuss these schedule compression techniques in detail, and present and validate a heuristic method to perform the combination of crashing, overlapping and substitution in a project schedule, to reach the maximum benefit while meeting the project target dates. Key words: schedule compression, acceleration, overlapping, crashing., Resume: La compression de l'echeancier est une tentative de reduire la duree des projets pour permettre une livraison precoce ou pour rattraper les delais encourus. Cela est normalement realise en [...]

Recently, a two-stage dynamic dense medium separator, called Tri-Flo, has become more applicable for treating difficult-to-wash coals. In this study, a 70-mm diameter transparent Tri-Flo separator was manufactured using prototyping and the effects of geometrical and operating parameters were investigated. Central composite design (CCD) was used in the experimental phase. The effects of internal tubes diameter, the installation slope, and the internal flow rate on the Tri-Flo performance were analyzed. CFD simulation was also used for better understanding of the flow pattern and interpretation of the experimental results. The results indicated that the air core diameter in both stages of the separator increases with all three variables. It was also found that medium recovery to float product in rougher and cleaner stages increases with unit inclination and internal tubes diameter, while it decreases with medium flow rate. The decrease in the air core size with increasing the feed tube diameter was an outstanding finding in both experiments and simulations. On average, a 16% decrease in the air core diameter was obtained when the feed tube diameter was increased from 23 mm to 26 mm. The results of the CFD simulation showed that there is a meaningful compatibility between the experimental observations and mathematical simulations. [ABSTRACT FROM AUTHOR]

The production yield and clean coal quality in dense-medium coal washing equipment such as three-product cylindrical separators are mainly controlled via the back-pressure adjustment at the sink port. However, the role of the back pressure in the fluid flow in such separators has been previously assessed only to a very limited extent. This study was undertaken to investigate the effect of back pressure on the flow pattern in a 70-mm three-product cylindrical separator. Accordingly, a time-dependent, three-dimensional numerical study was conducted based on computational fluid dynamics (CFD) in a two-phase system. The turbulence was simulated by the Reynolds stress model (RSM) whereas the volume of fluid (VOF) method was used to model the water–air interface. The simulation results were validated using the experimental data. The sensitivities of the flow fields and some other hydrodynamic characteristics to the increase of back pressure were different in the first and second stages of separator. Increase in the tangential velocity, the suppression of the air core and the improvement of medium recovery were some of the consequences of increasing the back pressure. [ABSTRACT FROM AUTHOR]

Background: Health tourism uses a set of services that promote the health and spirit of individuals through medical care. Entrepreneurship is a process of exploring and using value creation opportunities in the economic, cultural, social, and health sectors. The present study was done to investigate the development of Iran’s health tourism system based on Stevenson’s entrepreneurial management model and determine entrepreneurial opportunities during the COVID-19 outbreak. Methods: This descriptive quantitative research was conducted by the field study (survey) method, using a standardized and localized questionnaire from Stevenson’s entrepreneurial management model to examine the views of health tourism specialists as the statistical population of the study. Using the snowball sampling method, 357 health tourism specialists, university professors, and health system managers participated in this study from 2018 to 2020. The collected data were recorded in PLS Smart software and their analysis was performed using descriptive and inferential statistics. Results: The findings indicated that all six components of Stevenson’s entrepreneurial management had a significant effect on the health tourism industry’s development. Strategic orientation and commitment to opportunities (path coefficient: 0.83) had the maximum effect, while the reward philosophy (path coefficient: 0.41) had the minimum effect on developing the health tourism industry. Conclusion: The average status of Stevenson’s entrepreneurial management dimensions in the health tourism industry was evaluated. Some of these factors (strategic orientation and commitment to opportunities) were obviously more favorable than others. Proper entrepreneurial strategies and the use of situations can provide good opportunities in health tourism. [ABSTRACT FROM AUTHOR]

A linear fractional transportation problem in uncertain environment is studied in this paper where the uncertain parameters of the problem are of belief degree—based uncertainty. For the first time, this type of uncertainty is considered for the linear fractional transportation problem. Belief degree—based uncertainty is useful for the cases that no historical information of an uncertain event is available. Zigzag type uncertainty distribution is used to show the belief degree—based uncertainty of the parameters of the problem. As solution methodology, the uncertain linear fractional transportation problem is converted to a crisp form using three approaches of expected value model, expected value and chance-constrained model, and chance-constrained model, separately. An extensive computational study on a real illustrative example shows the efficiency of the proposed formulation and the conversion approaches. The sensitivity analysis over the example illustrates the high dependency of the objective function value to the changes of the confidence level values of the chance constraints in the expected value and chance-constrained programming approach and the chance-constrained programming approach. [ABSTRACT FROM AUTHOR]