Yayınlar

Links and identifiers

Tags and categories

BibTeX

@conference{sayginer2017b,
  title = {Fabrication of functionally graded ceramic- polymer dielectrics via freeze casting for RF applications},
  author = {Osman Sayginer and Gullu Kiziltas},
  year = {2017},
  journal = {Materials and Packaging},
  issn = {0272-9172},
  url = {http://2017apsursi.org/Papers/ViewPapers.asp?PaperNum=2593}
}

Links and identifiers

Tags and categories

BibTeX

@conference{sayginer2017a,
  title = {Integrated topology optimization of volumetric antenna substrates and conductor surfaces for broadband microstrip patch antennas},
  author = {Osman Sayginer and Gullu Kiziltas},
  year = {2017},
  journal = {Metamaterial Based Designs},
  url = {http://2017apsursi.org/Papers/ViewPapers.asp?PaperNum=1925}
}

Abstract

In parallel to current important developments in electronics and communication technologies, needs on wireless systems have become more popular yet stringent. In order to meet that demand, development of novel technologies and materials has become crucial. Patch antennas are widely used in the radio frequency (RF) industry. This is due to their simple shape, easy and low cost manufacturing capability and their suitability for conformal applications. However, most of current patch antenna designs rely on efforts puts towards their geometrical parameters with limited available dielectric materials in the market. This thesis mainly focuses on the topology optimization of polymer- ceramic composite substrates. These substrates allow for spatial dielectric permittivity variation via their functionally graded multilayer configuration with the objective to achieve minimization of reflected power at desired frequency values. Towards this goal in the proposed optimization study, Comsol Multiphysics 5.2 software was integrated with Matlab 2014b software and genetic algorithm was used as the optimization solver. In addition to the design study, in the second part of the thesis, a cooling system which allows for the adjustment of temperature values between 0℃ and -100℃ was designed to control the substrate properties of functionally graded materials (FGM) of ceramicpolymer antenna substrates, similar to those designed in the first part of the thesis. These substrates were produced via a novel manufacturing method based on freeze casting process. A new test platform was developed in order to investigate the effect of cooling rate and temperature on microporosity and permittivity of these substrate materials.

Links and identifiers

Tags and categories

BibTeX

@mastersthesis{sayginer2016,
  title = {Topology optimization and cooling system design for functionally graded patch antenna substrates},
  author = {Osman Sayginer},
  year = {2016},
  url = {http://research.sabanciuniv.edu/34797/}
}

Tags and categories

BibTeX

@conference{sayginer2013,
  title = {Resonance frequency analysis of MEMS based on piezoelectric microcantilever beam for vibration energy harvesting applications},
  author = {Osman Sayginer and Ugur Akyol},
  year = {2014}
}

Abstract

Titanium-based and cobalt-chrome alloys have been widely used in orthopaedic applications as these materials can significantly enhance the quality of human life as implant materials. The longevity of these materials is highly influenced by their mechanical properties. In some devices cobalt chrome components articulate with titanium alloy counter faces (e.g. in the taper connections of stems and femoral heads in modern modular designs) and damage has been reported of the harder cobalt chrome by the softer titanium alloy component. This study attempts to understand why this might occur by investigating bulk and surface mechanical properties (such as hardness and Young's modulus) of a number of hip implants and test samples using a Hysitron Triboindenter. AFM images were also obtained to determine the contact area and hence, pile-up correction factors.

The results were compared for samples before being used in the body, to account for surface mechanical response due to implant manufacture, and after, to account for the materials response to long-term cyclic loads. To assess the effects of oxidation, the alloys were treated electrochemically with Sodium-Chloride (NaCl) solution at body temperature. It was found that titanium oxidised preferentially compared with cobalt-chrome alloys. Furthermore, the oxidised titanium showed significantly higher hardness values therefore damaging the un-oxidised cobalt-chrome material. The implications for device design and manufacture are discussed.

Links and identifiers

Tags and categories

BibTeX

@article{moharrami2013does,
  title = {Why does titanium alloy wear cobalt chrome alloy despite lower bulk hardness: A nanoindentation study?},
  author = {N Moharrami and DJ Langton and O Sayginer and SJ Bull},
  year = {2013},
  journal = {Thin Solid Films},
  doi = {10.1016/j.tsf.2013.06.020},
  issn = {0040-6090}
}