Study on sterol fraction of commercial brands of milk,yoghurt and butter sold in Iranian market and chemometric data analysis

A gas chromatographic procedure for analysis of sterols was developed to detect possible addition of vegetable oils to milk, yoghurt and butter samples. The method involved fat extraction, saponification, hexane extraction, silylation of sterols and then analysis by gas chromatography. The sterol content of 102 samples of milk, yoghurt and butter was determined. Phytosterol content higher than 5% of total sterol was observed in four samples of milk and yoghurt. Principal component analysis showed that there was a direct relationship between the level of phytosterols and fat percentage in yoghurt samples. The described method is accurate and reliable enough to be employed regularly in food quality laboratories.     

Multi-site integrated production-distribution planning with trans-shipment: a fuzzy goal programming approach

In multi-site (parallel) manufacturing systems, each selling region (SR) is usually allocated to a specific manufacturing site (MS) in order to minimise the transportation costs, simplify the planning process, etc. However, such manufacturing systems usually encounter great drawbacks in terms of over-achievement or under-achievement of the forecasted demand due to isolation of the MSs. To cope with this drawback, this paper proposes a novel framework for preparing an optimal aggregate production plan by interconnecting the MSs through lateral trans-shipment. In the presence of fluctuating and dynamic demands, we apply some classic strategies including the inventory holding, back-ordering, and additional capacity options (i.e. overtime and changing workforce level) as well as lateral trans-shipment of products among MSs as the feasible strategies undertaken. Maximising the total profit and minimising the manufacturing lead time are considered as two managerial goals. Due to ambiguousness of some critical parameters as well as vagueness of objectives’ target values, a fuzzy goal programming (FGP) approach with imprecise goal hierarchy is developed for modelling the aggregate production-distribution planning (APDP) problem with trans-shipment. The proposed FGP model is then converted to an equivalent crisp one by combining the two recently developed fuzzy programming approaches. An illustrative example inspired by a real case study is provided to show the usefulness and applicability of the proposed model.     

A possibilistic approach for designing hybrid cellular manufacturing systems

In this paper, a hybrid cellular manufacturing (HCM) system is presented in which the main sources of uncertainty, e.g. the demands of parts and unit costs are treated as fuzzy numbers in the form of possibilistic distributions. The basic concept of HCM is that high variation in demand might disturb cell efficiency, so forming cells with only those parts that have stable demand, will profit. Thus, to design stable and robust manufacturing cells, a two-phase method is proposed in which a fuzzy adaptive ranking method is first applied to identify those parts with low and non-repetitive demands (i.e. the special parts) which will then be assigned to a functional cell. Afterwards, an interactive possibilistic programming model is applied to cell formation of remaining regular parts while considering both part sequences and multiple routes. To show the capability and usefulness of the proposed method, an illustrative example is also provided. Finally, concluding remarks are reported.     

Multi-site production planning integrating procurement and distribution plans in multi-echelon supply chains: an interactive fuzzy goal programming approach

Motivated by a real case of an automobile company, this study proposes a multi-objective, multi-site production planning model integrating procurement and distribution plans in a multi-echelon supply chain network with multiple suppliers, multiple manufacturing plants and multiple distribution centres. The model incorporates four important conflicting objectives simultaneously: minimisation of the total cost of logistics, maximisation of the total value of purchasing, minimisation of defective items and minimisation of late deliveries subject to some realistic constraints. Due to the imprecise/fuzzy nature of the objectives’ aspiration levels and some critical data, an interactive fuzzy goal programming formulation is first developed. Then, a novel fuzzy approach is proposed to convert the FGP model into an auxiliary crisp formulation to find an efficient compromise solution. The proposed model and solution method are validated through some numerical tests. Computational results indicate the practicality and tractability of the proposed model and also the superiority of the proposed auxiliary crisp formulation in contrast to the current alternative fuzzy approaches.     

Ultimate Bending Strength Evaluation of U-Notched Ductile Steel Samples Under Large-Scale Yielding Conditions

The load-bearing capacity of several U-notched specimens, reported in literature, made of very ductile steel and loaded under symmetric three-point bending were theoretically estimated by using the Equivalent Material Concept (EMC), proposed originally by the author, combined with two well-known brittle fracture models namely the mean stress (MS) and the point stress (PS) criteria. The results revealed that the MS-EMC model with an accuracy of more than 90% was more efficient than the PS-EMC model with about 72% accuracy. By using the MS-EMC model, one can predict well the onset of mode I cracking in U-notched ductile components under large-scale yielding conditions without requiring conducting elastic-plastic analyzes or using ductile fracture criteria.     

Effects of lanthanum strontium cobalt ferrite (LSCF) cathode properties on hollow fibre micro-tubular SOFC performances

Single layer La_0.6Sr_0.4Co_0.2Fe_0.8O₃ hollow fibre (HF) precursors (<1 mm ID) produced by phase inversion (PI) were sintered at 1,200, 1,350 and 1,400 °C. The increase in sintering temperature resulted in microstructural changes in the LSCF fibres, reflected in their electrical conductivities. LSCF-based cathodes with different designs were brushed onto co-extruded nickel–gadolinium-doped ceria (CGO) anode/CGO electrolyte dual-layer HFs (<1 mm ID) fabricated by PI. The effect of cathode layers on the overall performance of the fuel cells (FCs) was assessed using nearly identical anode and electrolyte compositions, thicknesses, and microstructures. Cathode microstructure design caused cells to perform differently producing peak power densities of 0.35–0.7 W cm⁻² at 600 °C. Impedance spectroscopy analysis at 600 °C on the FCs produced 0.12–0.24 Ω cm² confirming the cathode’s structural effect on the overall area-specific resistance of the FCs. The best performing FC with a brush-deposited cathode was compared to a similar FC where cathode was deposited by dip coating; at 600 °C the first produced 0.6 W cm⁻² while the second cell 0.7 W cm⁻². Co-extruding anodes and electrolytes by using PI and combining dip coating for cathode deposition could lead to the fabrication of FCs with enhanced microstructures and improved performances.     

The Evaluation of Variable-Injection Rate Waterflooding,Immiscible CO2 Flooding,and Water-alternating-CO2 Injection for Heavy Oil Recovery

Abstract

Despite the existence of studies for separate evaluation of waterflooding, immiscible CO₂ flooding, and CO₂ water-alternating gas (WAG) for heavy oil recovery, there is a lack of an experimental, comparative evaluation of these three methods. The authors conducted tests for comparative evaluation of variable-injection rate waterflood (VIWF), immiscible CO₂ flood, and CO₂ WAG. The results illustrate the (a) effectiveness of VIWF, immiscible CO₂ flood, and CO₂ WAG; (b) effect of permeability and oil viscosity on VIWF, immiscible CO₂ flood, and CO₂ WAG; (c) effect of injection rate on VIWF; and (d) effect of slug ratio on CO₂ WAG.     

A stacked neural network approach for yield prediction of propylene polymerization

Prediction of reaction yield as the most important characteristic process of a slurry polymerization industrial process of propylene has been carried out. Stacked neural network as an effective method for modeling of inherently complex and nonlinear systems–especially a system with a limited number of experimental data points–was chosen for yield prediction. Also, effect of operational parameters on propylene polymerization yield was modeled by the use of this method. The catalyst system was Mg(OEt)₂/DIBP/TiCl₄/PTES/AlEt₃, where Mg(OEt)₂, DIBP (diisobutyl phthalate), TiCl₄, PTES (phenyl triethoxy silane), and triethyl aluminum (AlEt₃) (TEAl) were employed as support, internal electron donor (ID), catalyst precursor, external electron donor (ED), and co‐catalyst, respectively. The experimental results confirmed the validity of the proposed model. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010