A fuzzy bi-objective mathematical model for optimum portfolio selection by considering inflation rate effects

Selecting and scheduling of project portfolios from a given set of investment proposals is one of the most important problems for which managers take several aspects into consideration. Inflation rate as one of these aspects is inherently uncertain, and because of this, various inflation rates can cause risky environments. Since risk can be decision driver for a proper selection, the purpose of this paper is fixed to minimize the risk and maximize the projects rate of return as two conflict objectives by considering inflation rate effects. A bi-objective mathematical programming model with fuzzy parameters is developed and well-known NSGA-II is applied to solve the developed model. Pareto plot of two conflict objectives helps decision maker (DM) to choose the best solution based on DM’s acceptable risk level. Moreover, the proposed model makes the project portfolio selection process more effective with developing a novel mathematical programming by sharing limited available budgets and resources. Finally, numerical results indicate the effectiveness of the proposed model with consideration the inflation rate effects on selecting project portfolios.     

A novel method for prediction of the critical diameter of solid pure and composite high explosives to assess their explosion safety in an industrial setting

ABSTRACT

For the explosion safety assessment in an industrial setting, the knowledge of critical diameter of high explosives provides important information on the sensitivity and conditions whereby detonations are likely to occur. The critical diameter or failure diameter is the minimum diameter of a cylindrical charge of high explosive which sustains a high order steady-state detonation. Available predictive methods require complex models, which are based on complicated variables such as the shock adiabat, and the generalized kinetic characteristic of decomposition of a high-explosive charge under shock-wave compression. For the first time, this paper describes a novel simple method for assessment of the critical diameter of pure and composite CHNO high explosives. The new model is based on the contribution of the number of nitrogen and oxygen atoms as well as some conditions, which are based on shock sensitivity, impact sensitivity and the negative values for core critical diameter of the desired explosives under certain situations. Experimental data of 42 high explosives have been used to derive and test the new model. The predicted critical diameters for building the model (29 explosives) and the test set (13 explosives), under the unconfined condition of these explosives, have the values of root-mean-square deviation (RMSD) of 5.14 and 3.96 mm, respectively.     

Improved Approach to Predict the Power of Energetic Materials

Nowadays, the ballistic mortar is the preferred test for the explosive power measurements but there is no reliable method for its prediction. For an energetic compound, the formation of low molecular mass gaseous products and a high positive heat of formation per unit weight of the energetic compound are important parameters to have a high value of power. A novel method was developed to predict the power by the ballistic mortar test for pure and mixture of energetic materials. It can be used for some important classes of energetic compounds including nitroaromatics, acyclic and cyclic nitramines, nitrate esters, and nitroaliphatics. The presented method is based on the molecular structure of the desired compound and there is no need to use experimental data such as the condensed phase heat of formation. For 84 pure and 24 mixtures of energetic compounds, the calculated power relative to 2,4,6‐trinitrotoluene (= 100) show good agreement with respect to the measured values.     

Comparison of Microparticles and Nanoparticles Effects on the Bonding of Roll Bonded IF Steel

In the present work, the effect of silicon carbide (SiC) particle size on the characteristics of cold roll bonded interstitial free (IF) steel strips, such as bond strength and peeled surface were carried out and compared to those of IF steel strip without particles. The bond strength was evaluated by the peeling test and scanning electron microscopy. It was found that with increasing thickness reduction, the bond strength of IF steel strips improved. The results also indicated that the presence of SiC particles (both micro and nano) decreased the bond strength of IF steel strips. Also, with increasing the particle size, the bond strength improved. It was found that for sample with microparticles compared to sample with nanoparticles, beyond the 80 % thickness reduction, a sudden increase in the average peel strength was observed. Finally, the results indicated that in the presence of nanoparticles between strips there were two types of unbonded area and the bond strength of these two areas was quite similar to each other.     

Organic Agriculture and Undernourishment in Developing Countries: Main Potentials and Challenges

While much has been published on the advantages of organic agriculture, less has addressed its potentials and challenges to fight undernourishment in developing countries. This article aims at reviewing the main potentials and challenges of this approach when dealing with “undernourishment” as a multifaceted concept in developing countries. Accordingly, 2 main issues of the concept which are “food security” and “food safety” are discussed in the context of both developed and developing countries to understand their different food policies’ priorities. Next, the main potentials, challenges and tradeoffs of the organic approach are analyzed to understand whether the approach is capable to provide a secure or a safe food-production system which can meet the food policy priorities in developing countries. With respect to food security, the article concludes that conventional and biotechnological approaches still produce higher yields than organic agriculture. However, considering the many advantages of organic agriculture, it can in a long run, be more conducive than now to meet food security. Thus, conventional approaches to feed the hungers in developing countries. Accordingly, the article emphasizes on the importance of providing farmers in developing countries with the possibility of implementing different approaches. Therefore, policy makers should be aware of a realistic and gradual transition from the other approaches to the organic that should be projected only in “long run,” and after conducting a series of risk assessment studies on the bases of both “crop-case” and “region-case.”     

Role of salt in Iranian ultrafiltered Feta cheese: Some textural and physicochemical changes during ripening

The effect of NaCl (0–4%) on the ripening of Iranian ultrafiltered (UF)‐Feta cheese was assessed over 120 days of ripening at 4 °C. Whey percentage, whey salt, whey pH, cheese pH and textural properties of hardness and cohesiveness were monitored, and experimental modelling performed using response surface methodology. Texture, pH and whey percentage were significantly affected by NaCl and ripening. The maximum whey of 22% was recorded at the end of ripening period. Texture of this cheese becomes harder during ripening confirming cheese pH and whey percentage being the major determining factors. Cheese samples were more elastic than viscous with cohesiveness values of 0.6–0.9.     

Relationship between dye sorption and morphology in polypropylene/poly (butylene terephthalate) microfibrillar blend nanocomposite fibers

In this research work, the relation between microstructural enhancement and dyeing behavior of immiscible blend nanocomposite fibers was investigated using scanning electron microscopy, transmission electron microscopy, X-ray diffraction patterns, and rheometric mechanical spectrometer along with quantitative analysis of dye sorption. A novel microfibrillar morphology blend fiber, in which poly (butylene terephthalate) nanocomposite fibrils uniformly distributed in the cross section of polypropylene matrix, was successfully developed using melt compounding process. Preferred location of nanoclay had improving effect on poly (butylene terephthalate) fibril formation such that there was an organoclay concentration above that fiber with fine microfibrillar morphology could hardly be produced. It was demonstrated that nanoclay melt intercalation and partitioning controlled the activation energy of dyeing. The maximum sorption rate was achieved by utilizing compatibilizer to transfer part of nanoclay platelets into the polypropylene matrix.     

Novel functionalized bis(imino)pyridine cobalt(II) catalysts for ethylene polymerization

This report describes synthesis and ethylene polymerization in the various conditions by two novel 2,6-bis(imino)pyridine (BIMP) catalysts B and C based on cobalt activated by methylaluminoxane (MAO) in a slurry semi-batch reactor. The catalyst activities as well as polymer properties were affected dramatically by electronic effects of the attached substitutions on the para-position of the pyridine ring. Theoretical study exhibited more positive charge on the central metal of the catalyst B resulted in higher activity at the expense of lower thermal stability and lifetime. The polymer obtained using the catalysts exhibited high molecular weight and almost narrow molecular weight distribution (MWD) ranging from 2.35 to 4.10 at the employed polymerization conditions. The highest and lowest molecular weight of the obtained polymers were produced by the catalyst A and C respectively. Hydrogen could slightly increase the catalyst activities with the exception of the catalyst B. The catalyst C bearing electron-donor OMe substitution at the para-position of the pyridine ring, produced PE with narrower PDI relative to the polymer resulted by catalysts A and B.     

The impact of project capabilities on project performance: Case of open source software projects

Open Source Software (OSS) projects are contingent on volunteer developers and voluntary contributions from users, accordingly, traditional performance measures used for software projects, like being on time and budget, and satisfying specifications, may not be relevant for such projects. Although researchers have studied some predictors of OSS project performance, there is a lack of empirical work that studies the impact of project capabilities on the performance of OSS projects. Therefore, this paper studies project capabilities as potential predictors of OSS project performance. The data, gathered from 607 OSS projects over time (in two snap-shots), were consistent with Dynamic Capability Theory (DCT). In other words, the results showed that in order to achieve higher project performance, OSS projects need to have strong capabilities in terms of proactive and efficient defect-removal as well as proactive and efficient functionality-enhancement. The implications of these results for the OSS research community are discussed, followed by recommendations for OSS practitioners.     

A methodology for selecting portfolios of projects with interactions and under uncertainty

Effective project evaluation and selection strategies can directly impact organizational productivity and profitability. Numerous analytical techniques ranging from simple weighted scoring to complex mathematical programming approaches have been proposed to solve these problems. However, traditional project selection methods too often fail to consider both the uncertainties in projects and the interaction among projects. Some prior studies have considered the interaction among projects in deterministic environments. Others have dealt with stochastic environments but have not considered project interdependencies. This study aspires to fill this gap in the project portfolio selection literature. Information system/information technology (IS/IT) projects are used in this study because they are frequently subject to uncertainties due to estimation difficulties and bounded by interactions due to technological interdependencies. We use Data Envelopment Analysis (DEA) to select the best portfolio of IS/IT projects while taking both project uncertainties (modeled as fuzzy variables) and project interactions into consideration simultaneously. We also present a numerical example to demonstrate the applicability of the proposed framework and exhibit the efficacy of the procedures.