فهرست مطالب

  • Volume:3 Issue:1, 2007
  • تاریخ انتشار: 1386/06/20
  • تعداد عناوین: 7
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  • Abdullah Keyvani Page 3
    In spite of the fact that cementitious and concrete materials are mainly used on a large scale and inhuge quantities for roads, dams, bridges and building constructions, the mechanical behavior of thesematerials depends to a great extend on structural elements and phenomena which are effective on amicro and nanoscale. Although this is well known by researchers, material producers and engineersfor many years, the aspect of nanoscience and nanotechnology has hardly found any special attention,so far. New efforts and possibilities of material engineering on nanoscale in other fields may well leadto a new leap forward to improve mechanical and physical properties as well as durability of thisimportant group of composite construction materials. This paper intends to stimulate the applicationand development of nanoscientific and nanotechnological concepts of nanofiber materials and theirapplications in concrete. Due to the wide range of possibilities, however, it does not claim to presenta complete overview of the whole field. This would clearly go beyond the scope of this paper. It rathergives a short outline on the related cementitious and concrete material problems and research topicswhere nanoscience and nanotechnology could produce a major contribution to improve the nanofibrousmaterials where research needs to be done. Capability to accurately predict failure in joints offerssignificant potential for developing higher performance structural designs that are safer at the same timesince these nanotubes can be used to accurately assess the behavior of joints, members and structures.Nanofibrous cement based materials can monitor regions of partial damages, localized changes instrains, stresses and temperatures of any joints and members.
  • A. Amrollahia., A .Hamidi, A.M.Rashidi Page 13
    In this investigation the silicate nano structure of MCM-41 has been used for the production of nanofluid.The particles have negligible heat conductivity and therefore by their dispersion in a base fluid likewater, it is possible to study the increase of heat conductivity due to the Brownian motion effects. In thiswork a suitable apparatus for the measurement of heat conductivity has been built and calibrated andthen using the apparatus and preparing suitable nanofluids, the conductivity and the volumetric heatcapacities have been measured. Experimental results show that the preparation time of the nanofluidusing the ultrasonic method has pronounced effect on the increase of the conductivity. A twenty fourhours preparation time for the nanofluid containing 2.5% (vol) of the particles results in a 7% increasein the conductivity of the base fluid while showing no significant increase in the volumetric heat capacity.Investigating the effect of increasing the temperature and volumetric percentage of the particles it canbe deduced that Brownian nano particles movement is one of the main factors in increasing the thermalnanofluids conductivity.Keywords: Nanofluid, Nano particles, Effective thermal conductivity, Specific heat capacity.
  • Hamid Ramezani, Mohammad, Reza Saberi, G. Ali Mansoori Page 21
  • N.Jeyakumaran, B.Natarajan, S.Ramamurthy, V.Vasu Page 45
  • Sh. Jamali, E. Saievar, Iranizad, S. Farjami Shayesteh Page 53
  • N.Bhullar, M.G.H.Zaidi, S.Alam R. Singh Page 63