@article{ChenSchwingKarlovšeketal.,
  author    = {Chen, Zhen and Schwing, Moritz and Karlovšek, Jurij and Wagner, Norman and Scheuermann, Alexander},
  title     = {Broadband Dielectric Measurement Methods for Soft Geomaterials: Coaxial Transmission Line Cell and Open-Ended Coaxial Probe},
  series = {International Journal of Engineering and Technology},
  volume    = {2014},
  journal   = {International Journal of Engineering and Technology},
  number    = {volume 6, number 5},
  doi       = {10.7763/IJET.2014.V6.728},
  url       = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20210408-43984},
  pages     = {373 -- 380},
  abstract  = {Broadband dielectric measurement methods based on vector network analyzer coupled with coaxial transmission line cell (CC) and open-ended coaxial probe (OC) are simply reviewed, by which the dielectric behaviors in the frequency range of 1 MHz to 3 GHz of two practical geomaterials are investigated. Kaolin after modified compaction with different water contents is measured by using CC. The results are consistent with previous study on standardized compacted kaolin and suggest that the dielectric properties at frequencies below 100 MHz are not only a function of water content but also functions of other soil state parameters including dry density. The hydration process of a commercial grout is monitored in real time by using OC. It is found that the time dependent dielectric properties can accurately reveal the different stages of the hydration process. These measurement results demonstrate the practicability of the introduced methods in determining dielectric properties of soft geomaterials.},
  subject      = {Impedanzspektroskopie},
  language  = {en}
}
@article{BumbergerMaiSchmidtetal.,
  author    = {Bumberger, Jan and Mai, Juliane and Schmidt, Felix and L{\"u}nenschloß, Peter and Wagner, Norman and T{\"o}pfer, Hannes},
  title     = {Spatial Retrieval of Broadband Dielectric Spectra},
  series = {Sensors},
  journal   = {Sensors},
  doi       = {10.3390/s18092780},
  url       = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20180906-37831},
  pages     = {1 -- 22},
  abstract  = {A broadband soil dielectric spectra retrieval approach ( 1 MHz- 2 GHz) has been implemented for a layered half space. The inversion kernel consists of a two-port transmission line forward model in the frequency domain and a constitutive material equation based on a power law soil mixture rule (Complex Refractive Index Model - CRIM). The spatially-distributed retrieval of broadband dielectric spectra was achieved with a global optimization approach based on a Shuffled Complex Evolution (SCE) algorithm using the full set of the scattering parameters. For each layer, the broadband dielectric spectra were retrieved with the corresponding parameters thickness, porosity, water saturation and electrical conductivity of the aqueous pore solution. For the validation of the approach, a coaxial transmission line cell measured with a network analyzer was used. The possibilities and limitations of the inverse parameter estimation were numerically analyzed in four scenarios. Expected and retrieved layer thicknesses, soil properties and broadband dielectric spectra in each scenario were in reasonable agreement. Hence, the model is suitable for an estimation of in-homogeneous material parameter distributions. Moreover, the proposed frequency domain approach allows an automatic adaptation of layer number and thickness or regular grids in time and/or space.},
  subject      = {Theoretische Elektrotechnik},
  language  = {en}
}