A linear programming model to optimize the decision-making to managing cogeneration system

A mathematical linear programming (LP) model was developed to optimize the decision-making for managing a cogeneration facility as a potential clean-development mechanism project in a hospital in Palestine. The model was developed to optimize the cost of energy and the cost of installation of a small cogeneration plant under constraints on electricity-and-heat supply and demand balances. In the model, the sources of electricity are either from cogeneration or public utilities and it was calculated the least cost to supply electricity and heat to the hospital. The hospital is using heat for their operation and that made the application for the cogeneration to be attractive and feasible. In this study, we will develop the LP model and will show the results and the time schedule for the cogeneration. This developed LP model can be used and run to any cogeneration application with little modification.     

Vibration Characteristics of K?mürhan Highway Bridge Constructed with Balanced Cantilever Method

K?mürhan Highway Bridge is a reinforced concrete box girder bridge located on the 51st km of Elaz??–Malatya Highway over the F?rat River. Because of the fact that the K?mürhan Bridge is the only bridge in this part of F?rat, it has major logistical importance. So, this paper aims to determine dynamic characteristics such as natural frequencies, mode shapes, and damping ratios of the bridge using experimental measurements and finite-element analyses to evaluate current behavior. The experimental measurements are carried out by ambient vibration tests under traffic loads. Due to the expansion joint in the middle of the bridge, special measurement points are selected and experimental test setups are constituted. Vibration data are gathered from the both box girder and bridge deck. Measurement time, frequency span, and effective mode number are determined by considering similar studies and literature. The peak picking method in the frequency domain is used for the output-only modal identification. An analytical modal analysis is performed on the developed two- and three-dimensional finite-element model of the bridge using SAP2000 software to provide the analytical frequencies and mode shapes. At the end of the study, dynamic characteristics of the Elaz?? and Malatya parts of the bridge obtained from the experimental measurements are compared with each other and transverse effects on the bridge are determined. Also, experimental and analytical dynamic characteristics are compared. Good agreement is found between dynamic characteristics in the all measurement test setups performed on the box girder and bridge deck and analytical modal analyses.     

Estimation of uncertainty with the modulus of elasticity measured by means of tensile test for BSCCO tapes

The international round robin test (RRT) was conducted in order to establish the international standard for the tensile test method for BSCCO-2223 tape shaped wires. The measurands of mechanical properties were statistically analyzed to estimate their standard uncertainties and their correlation among laboratories. Consequently the large variance was observed with the modulus of elasticity determined from the initial loading curve. The reason has been examined by estimating type B uncertainties causing at every step of the experimental procedure. With respect to the modulus of elasticity, the grand intra-lab average of relative standard uncertainty (RSU) obtained from the RRT coincided roughly with that derived by means of type B evaluation. Thus it is emphasized that the type B evaluation is very effective tool for expecting the uncertainties of the observations like the modulus of elasticity. On the other hand, the grand over-all RSU was larger than the grand intra-lab one. The combined standard uncertainties were calculated by changing the strain rate, but kept other parameters constant. In order to suppress the influence from the strain rate to the variance, it has been recommended that the strain rate shall be regulated less than 2 × 10⁻⁴ 1/s in the tensile test method.     

Die elektrolytische Dissoziation flüssiger Schlacken und ihre Bedeutung für metallurgische Reaktionen

Ableitung eines mathematischen Transportmodells des Schwefels für die zeitlich quantitative Angabe der Schwefelverteilung zwischen Metall und Schlacke. Stand der heutigen Erkenntnisse für den Entschwefelungsmechanismus zwischen Bad und Schlacke. Angabe von allgemeinen Transportgleichungen des Schwefels ohne und mit Berücksichtigung der Diffusion des Schwefels im Metall und in der Schlacke. Erörterung des Schwefeltransportes zwischen kohlenstoffgesättigten Eisenschmelzen und flüssigen kalkhaltigen Schlacken. Bedeutung des Einflusses von Silizium auf die Schwefelaktivität und für die Grenzflächenreaktionen. Kritische Betrachtung zur Definition der Gleichgewichtskennzahl K_Si,S.     

Reliable design of a closed loop supply chain network under uncertainty: An interval fuzzy possibilistic chance-constrained model

This article seeks to offer a systematic approach to establishing a reliable network of facilities in closed loop supply chains (CLSCs) under uncertainties. Facilities that are located in this article concurrently satisfy both traditional objective functions and reliability considerations in CLSC network designs. To attack this problem, a novel mathematical model is developed that integrates the network design decisions in both forward and reverse supply chain networks. The model also utilizes an effective reliability approach to find a robust network design. In order to make the results of this article more realistic, a CLSC for a case study in the iron and steel industry has been explored. The considered CLSC is multi-echelon, multi-facility, multi-product and multi-supplier. Furthermore, multiple facilities exist in the reverse logistics network leading to high complexities. Since the collection centres play an important role in this network, the reliability concept of these facilities is taken into consideration. To solve the proposed model, a novel interactive hybrid solution methodology is developed by combining a number of efficient solution approaches from the recent literature. The proposed solution methodology is a bi-objective interval fuzzy possibilistic chance-constraint mixed integer linear programming (BOIFPCCMILP). Finally, computational experiments are provided to demonstrate the applicability and suitability of the proposed model in a supply chain environment and to help decision makers facilitate their analyses.     

Investigation of turbulent premixed methane/air and hydrogen-enriched methane/air flames in a laboratory-scale gas turbine model combustor

Methane and hydrogen-enriched (25 vol% and 50 vol% H₂-enriched CH₄) methane/air premixed flames were investigated in a gas turbine model combustor under atmospheric conditions. The flame operability ranges were mapped at different Reynold numbers (Re), showing the dependence on Re and H₂ concentrations. The effects of equivalence ratio (Φ), Re, and H₂ enrichment on flame structure were examined employing OH-PLIF measurement. For CH₄/air cases, the flame was stabilized with an M shape; while for H₂-enriched cases, the flame transitions to a П shape above a specific Φ. This transition was observed to influence significantly the flashback limits. The flame shape transition is most likely a result of H₂ enrichment, occurring due to the increase in flame speed, higher resistance of the flame to the strain rate, and change in the inner recirculation zone. Flow fields of CH₄/air flames were compared between low and high Re cases employing high-speed PIV. The flashback events, led by two mechanisms (combustion-induced vortex breakdown, CIVB, and boundary-layer flashback, BLF), were observed and recorded using high-speed OH chemiluminescence imaging. It was found that the CIVB flashback occurred only for CH₄ flames with M shape, whereas the BLF occurs for all H₂-enriched flames with П shape.     

Acrylonitrile/vinyl acetate copolymer nanofibers with different vinylacetate content

In this study, free radical copolymerization of acrylonitrile (AN)–vinyl acetate (VAc) was performed for five different feed ratio of VAc (wt %) by using ammonium persulfate (APS) in the aqueous medium. The effect of VAc content on the spectrophotometric and thermal properties of AN–VAc copolymers was investigated by Fourier Transform Infrared–Attenuated Total Reflectance spectrophotometer (FTIR–ATR), differential scanning calorimeter (DSC), and thermal gravimetric analyzer (TGA). Thermal stability of homopolymer of AN is improved after being copolymerized. The electrospun P(AN‐co‐VAc) nanofibers were fabricated and the effect of VAc content on the morphologic properties of nanofibers was studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The viscosity of the solution had a significant effect on P(AN‐co‐VAc) electrospinning and the nanofiber morphology. The average diameters of P(AN‐co‐VAc) nanofibers decreased 3.4 times with increasing feed ratio of VAc wt %. The P(AN‐co‐VAc) electrospun nanofiber mats, with the feed ratio of 30 wt % VAc, can be used as a nanofiber membrane in filtration and as a carbon nanofiber precursor for energy storage applications due to high surface to volume ratio, high thermal stability, homogeneous, and thinner nanofiber distribution. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Analysis of maintenance of redundant genetic structures in the yeast Saccharomyces cerevisiae: disomy and spontaneous mitochondrial rho(-)-mutability

With the postmeiotic progeny of triploids used as initial material, n + 1 disomics at chromosomes II, III, VII, VIII, and X were isolated. Disomy at the chromosomes listed (as well as for chromosomes IV and XIV, as demonstrated previously) is associated with decreased spontaneous rho- mitochondrial mutability. This suggests that a disturbance of the chromosome balance itself as such can lead to considerable changes in the spontaneous variability of the mitochondrial genome. From crosses between n + 1 disomics at chromosome IV and for each of the remaining above-mentioned six chromosomes, double n + 2 disomics were isolated, carrying nonchromologous pairs of extra chromosomes. Analysis of mitotic stability of the chromosome IV and spontaneous rho- mutability in double disomics shows that the effect of disomy on spontaneous rho- mutability most probably cannot be explained by direct competition between different genetic structures maintained in Saccharomyces cerevisiae cells. Disturbance of the chromosome balance in disomy is accompanied by essential qualitative changes in processes mediating the maintenance of genetic structures in yeast cells.