Showing papers by "University of Tabriz published in 1988"

Synthesis and characterization of styrene-based polymer supports

Abstract: A number of reactive styrene derivatives 3a – h was synthesized and copolymerized in suspension with styrene and divinylbenzene to produce beaded styrene-based resins 5a – h, carrying bromo, methoxy, chloromethyl, hydroxymethyl, hydroxyethyl, or α-hydroxy-4-methoxybenzyl groups. The swelling behaviour of selected samples of these resins was studied in tetrahydrofuran, toluene, dichloromethane, dioxane, ethyl acetate, dimethylformamide, and methanol. Swellability data are given for resin samples having different percentages of crosslinking and for those produced in the presence of chlorobenzene as a monomer diluent (or polymerization solvent). The significance of the swellability data are briefly discussed in terms of the nature of solvent, the degree of crosslinking and the effect of the monomer diluent on the matrix structure. Details of a series of model reactions of the resin-bound functional groups are also given, and the results are discussed on the basis of resin swellability and polymer-substrate compatibility.

Application Of Multi-attribute Fuzzy Decision Analysis In Engineering

Abstract: Multi-attribute fuzzy decision analysis is utilized to develop a new interactive cumputer program by assuming that the decision-maker has fuzzy idea about the weightings of the respective criterias and rating of alternatives. In order to demonstrate the capability of this package, an electric power companys' expansion program for the supplying of electric power to the load center is used as an example. The decision-maker can select his/her verbal ratings of the alternatives and verbal weighting of the criterias as an input to the computer. Then, the ranking of alternatives along with the degree of preferability of best alternative relative to the others is read out.

The temperature dependences of permittivity and a.c. conductivity in Ca−Al−Si oxynitride glasses

Abstract: The temperature dependence of the permittivity and conductivity of a Ca-Al-Si oxynitride glass has been measured between 200 and 500° C at frequencies covering the range 0.5 to 10 kHz. A d.c. component of the conductivity has been extracted which has an activation energy of 1.6 ± 0.2 eV for the associated charge carriers, and the remaining dielectric conductivity is shown to vary with frequency in a manner consistent with the presence of loss peaks, the loss-peak frequency having a thermal activation of 0.9 ± 0.1 eV. Below and above the resonant loss frequencies, the dielectric loss shows power-law behaviour. Comparisons are presented with other results on oxynitride and normal oxide glass and with silicon nitride.

Reliability and Availability Analysis of Fusion Power Plants

Abstract: Major efforts are underway to develop fusion energy for use in electric power production in the furture. While fusion reactor concepts are being developed, appropriate attention must be given to problems relvant to the utility requirements which are likely to be encountered in the commercialization phase. In this paper the expected fusion plant availability is assessed in detail due to the importance of power plant availability in the commercialization of the use of any energy source. The reliability and availability of fusion plants are analyzed by using the PREP, KITT–1, and KITT–2 codes (1). Analysis of computer output yields the availability of 82–82.9 percent for a fusion power plant under investigation during one year operation by assuming that there would be two schedule outages for first wall replacement. Also, Exploration of those components which are prone to failure and which may increase the change for forced failures is made.

Flow and Pressure Distributions in Short Heat Exchanger Cores with Abrupt Entrance and Exit

Abstract: The typical installation of a heat exchange device usually involves a flow contraction at the core entrance and a flow expansion at the core exit. Repeated flow Contraction and expansion are experienced in the flow passages of some compact heat exchangers. The latter refers to the flow passages in the plate-fin type with louvered fins or stripped fins and in the tubular type with dimpled-circular or flat tubes. Similar flow situations are encountered in flat-edged orifices. The majority of these constrictions are characterized by small length-to-hydraulic diameter ratio so that the flow after being disrupted has a little time in developing into an appropriate pattern before it is disrupted again. This work deals with a flow system consisting of a parallel channel with a flow constriction of small . The flows at both ends of the channel are laminar, fully developed. The full Navies-Stokes equations for the steady two-dimensional flow are solved numerically using the finite-difference technique. Some preliminary results are obtained for the distributions of velocity components, streamline and pressure. The result for a flow of small Reynolds number show qualitative agreement with the flow pattern of a similar flow system obtained by visualization method.