Modelling and optimization of district heating and industrial energy system—an approach to a locally deregulated heat market

Regions with densely concentration of industries and district heating systems (DHS) could be interesting study object from the light of an integrated heat market on local basis. System analysis with a widened system boundary could be used as an approach to evaluate the benefit of an integrated heat supply system. In this study, an energy system model consisting of totally seven different participants is designed and the optimization results of the system analysis are presented. With applied data and assumptions, the study shows that a significant amount of the heat demand within two sub‐systems can be covered by heat supply from the heat market (the entire heat comes from two industries). Shadow prices, which can be used for heat pricing, indicate the advantage of an integrated system. The system cost reduction through integration and the availability of several actors with diverse energy supply system, makes the region under study an interesting area to prove a locally deregulated heat market. Copyright © 2004 John Wiley & Sons, Ltd.     

Accuracy of a class of concurrent algorithms for transient finite element analysis

The accuracy of a new class of concurrent, procedures for transient finite element analysis is examined. A phase error analysis is carried out which shows that wave retardation leading to unacceptable loss of accuracy may occur if a Courant condition based on the dimensions of the subdomains is violated. Numerical tests suggest that this Courant condition is conservative for typical structural applications and may lead to a marked increase in accuracy as the number of subdomains is increased. Theoretical speed-up ratios are derived which suggest that the algorithms under consideration can be expected to exhibit a performance superior to that of globally implicit methods when implemented on parallel machines.     

A semi-theoretical and experimental approach for the determination of the stress intensity factors

The stress intensity factors for plexiglass plates containing edge cracks and subjected to either pure bending or tension are determined herein. The method of investigation was based on a semi-theoretical and experimental approach, where the stress intensity factors are expressed in terms of the measured diameter of the caustic, the crack length, and the width of the specimen. First, two basic crack arrangements (single and double edge cracks) were studied and then the method was utilized for the investigation of more complicated crack arrangements which are difficult or maybe impossible to be investigated otherwise. In particular, the stress intensity factor for plates having a sharp V-notch of various angles θ, and semi-infinite plates containing equal parallel edge cracks subjected to pure bending and tension respectively, were investigated in order to verify the validity of this method.     

Soy protein supplementation does not cause lymphocytopenia in postmenopausal women

Background  

The health benefits of soy isoflavones have been widely investigated; however, there are some concerns as to whether soy isoflavones, similar to ipriflavone, a synthetic isoflavone, cause lymphocytopenia in postmenopausal women. Hence, the purpose of this study was to investigate the extent to which 12-month supplementation of 25 g soy protein containing 60 mg isoflavones alters lymphocyte counts or other hematological parameters in postmenopausal women who were not on hormone replacement therapy.     

Microstructure evolution and simulation of copolymerization reaction using a percolation kinetic gelation model

A new kinetic gelation model that incorporates the kinetics of non-linear free radical copolymerization is presented. Copolymerization of bi- and tetrafunctional monomer mixtures is simulated to characterize kinetic effects on polymerization statistics and microstructures. An algorithm for random next step selection in a self-avoiding random walk and efficient mechanisms of component's mobility are introduced to improve the universality of the predictions by removing commonly occurring simulation deficiencies due to early trapping of radicals. The model has the capability to predict the onset of the sol-gel transition, and the effect of chemical composition on the transition point. It is shown that a better understanding of microstructure evolution during polymerization and chemical gelation is attained. Lastly, one important benefit of the simulation method is the ability to simulate very highly packed random chains or microgels within a polymer network.     

The effect of ZIF-90 particle in Pebax/Psf composite membrane on the transport properties of CO2, CH4 and N2 gases by Molecular Dynamics Simulation method

Nowadays, mixed matrix membranes (MMMs) have considered by many researchers to overcome the problems of polymeric membranes. In addition, molecular dynamics (MD) and Monte Carlo (MC) simulation Methods are suitable tools for studying transport properties and morphology in MMMs. For this purpose, in this study using material studio 2017 (MS) software, the transport properties of CO₂, CH₄ and N₂ in Pebax, Psf neat Pebax/Psf composite and Pebax/Psf composite filled with ZIF-90 particles have been investigated. By adding Psf to Pebax matrix, the selectivity of CO₂/CH₄ and CO₂/N₂ gases has significantly increased. In addition, adding ZIF-90 particles to the Pebax/Psf composite increased the permeability of CO₂, CH₄ and N₂ compared to neat and composite membranes. The morphological properties of the membranes, such as the fractional free volume (FFV), radial distribution function (RDF), glass transition temperature (T_G), X-ray diffraction (XRD) and equilibrium density have calculated and acceptable results have obtained.     

A two dimensional investigation on plates with oblique equal and unequal parallel edge cracks subjected to tension

This paper reports on an attempt to investigate the stress intensity factors of equal and unequal oblique parallel edge cracks subjected to tension. The effects of the variation of the length of the cracks, angle of inclination, and crack spacings on the stress intensity factors (opening and sliding modes) were studied. Experimental observations show that, for crack spacings equal or larger than the length of the equal oblique parallel edge cracks, the size of the caustics for the cracks in the loaded specimen approach that of a single oblique edge crack with the same angle of inclination.In the case of unequal oblique parallel edge cracks, a crack closure phenomenon and its occurrance with respect to the length of the cracks and crack spacings were investigated. It was observed that the transverse diameter of the caustic for the shorter cracks became small and negligible when the position of the shorter cracks with respect to the longer cracks became smaller than half of the crack spacings.

---

Résumé Le mémoire est relatif à une tentative d'étude des facteurs d'intensité de contrainte relatifs à des fissures de bord parallèles et obliques de longuers égales et inégales soumises à tension. On étudie les effets de la variation de longueurs des fissures, de l'angle de leur inclinaison, et de la distance entre les fissures sur les facteurs d'intensité de contrainte dans les modes d'ouverture et de glissement. Les observations expérimentales montrent que lorsque les fissures sont espacées d'une grandeur égale ou supérieure à la longueur des fissures de bord obliques parallèles et égales, la dimension des caustiques relatives aux fissures dans une éprouvette sous charge est proche de celle relative à une fissure de bord simple oblique possédant le même angle d'inclinaison.Dans le cas de fissures de bords parallèles obliques inégales, un phénomène de fermeture de fissure a été étudié, ainsi que son apparition en fonction de la longueur des fissures et de l'espacement entre celles-ci. Il a été observé que le diamètre transversal de la caustique relative aux fissures plus courtes devient faible et négligeable lorsque la position des fissures courtes par rapport aux fissures les plus longues devient plus petite que la moitié de l'espacement entre les fissures.

     

Thermosensitive nanoparticles prepared from poly(N‐isopropylacrylamide‐acrylamide‐vinilpyrrolidone) and its blend with poly(lactide‐co‐glycolide) for efficient drug delivery system

Temperature‐responsive polymers have become increasingly attractive as carrier for the injectable drug delivery systems. In the present work, we have studied the preparation of poly(N‐isopropylacrylamide‐acrylamide‐vinilpyrrolidone) (NIPAAm‐AAm‐VP terpolymer) nanoparticulated terpolymer and its blend with poly(lactide‐co‐glycolide, PLGA; molar ratio of lactide/glycolid 1/3). Thermosensitive terpolymer, poly(NIPAAm‐AAm‐VP) was prepared by free‐radical polymerization in aqueous solution. The nanoparticles of poly(NIPAAm‐AAm‐VP) and its blend with PLGA containing naltrexone were prepared using the evaporation and w/o emulsion‐solvent evaporation methods, respectively. Nanoparticles prepared from terpolymer‐PLGA blend at low polymer concentration (5%) shows larger particle size (>300 nm) and higher drug content%. Various types of nanoparticles showed a burst release of less than 10% after 24 h . The results suggest that by regulating different variables, desired release profiles of naltrexone can be achieved using a blend of PLGA‐poly(NIPAAm‐AAm‐VP) nanoparticulate system. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Novel numerical solutions of nonlinear heat transfer problems using the linear barycentric rational interpolation

In this investigation, a numerical technique to obtain the approximate solutions of four well‐known nonlinear differential equations in the area of heat transfer is presented. This method is based on the operational matrix of derivative of linear barycentric rational interpolation. The main advantages of this approach are that it uses the Floater‐Hormann weights, which are very efficient in practice, and reduces the governing differential equation to a system of algebraic equations. The results are compared with the obtained numerical results of the fourth‐order Runge‐Kutta method along with the shooting method and some of the previously existing methods. The acquired results reveal that the derivative operational matrix method with barycentric rational basis functions is very efficient and can be implemented easily and fast.     

Determining the occurrence time of different stages of asphaltene aggregation using molecular dynamics simulations

This work presents a framework for future studies to better understand the appropriate time to include chemical inhibitors at different stages of asphaltene aggregation in the oil. For this purpose, molecular dynamics (MD) simulations were performed to study the aggregation of asphaltene molecules in heptane, in terms of strength, dynamics, and the occurrence time of each stage of aggregation from single molecules to a large flocculate. Results indicate that the nucleation of nanoaggregates begins prior to 10?ns, clusters start forming at 98?ns, and flocculation happens after 120?ns. It was also observed that the final flocculate had a globular shape.