TY - CONF A1 - Adão, Filipe Jorge Santos Ferreira A1 - Rosemarie, Helmerich A1 - Gerrit, Voigt A1 - Laura, Moldenhauer A1 - Neumann, Patrick P. ED - Motavalli, M. ED - Ilki, A. T1 - Humidity monitoring in concrete using Bluetooth Low Energy sensors T2 - SMAR 2017 N2 - The vulnerability of low quality concrete to changing weather conditions is well known. The constant exposure to temperature changes, biological activity, and humidity ends up in damage to buildings and structures which contain this material. It is therefore necessary to take preventive measures to control the extent of the damage done by weathering and possible penetration of adverse chemicals into structures which need public safety. The Federal Institute for Materials Research and Testing (BAM), in cooperation with the small enterprise LinTech GmbH, is working on a project to monitor humidity changes in concrete by analyzing the changes in signal strength (RSSI) from Bluetooth Low Energy sensors. In this paper, we show results which demonstrate the influence of changing water content in concrete on the received RSSI. We observed that as water content in concrete decreases, the received RSSI improves. However, the damping effect is not linearly proportional to water content, rather exponentially proportional. This suggests that changes in the received signal strength are more easily observed when water content in concrete is higher. Finally, we reconstructed a RSSI distribution map using computed tomography. T2 - SMAR 2017 CY - Zurich, Switzerland DA - 13.09.2017 KW - Bluetooth Low Energy Computed Tomography KW - RSSI KW - Concrete KW - Water KW - Monitoring KW - Computed Tomography PY - 2017 UR - http://www.smar-conferences.org/smar/SMAR_2017_Proceedings/papers/153.pdf VL - 2017 SP - 1 EP - 8 CY - Zurich, Switzerland AN - OPUS4-43597 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Adão, Filipe Jorge Santos Ferreira A1 - Helmerich, Rosemarie A1 - Voigt, Gerrit A1 - Moldenhauer, Laura A1 - Neumann, Patrick P. T1 - Humidity monitoring in concrete using Bluetooth Low Energy sensors N2 - The vulnerability of low quality concrete to changing weather conditions is well known. The constant exposure to temperature changes, biological activity, and humidity ends up in damage to buildings and structures which contain this material. It is therefore necessary to take preventive measures to control the extent of the damage done by weathering and possible penetration of adverse chemicals into structures which need public safety. The Federal Institute for Materials Research and Testing (BAM), in cooperation with the small enterprise LinTech GmbH, is working on a project to monitor humidity changes in concrete by analyzing the changes in signal strength (RSSI) from Bluetooth Low Energy sensors. In this paper, we show results which demonstrate the influence of changing water content in concrete on the received RSSI. We observed that as water content in concrete decreases, the received RSSI improves. However, the damping effect is not linearly proportional to water content, rather exponentially proportional. This suggests that changes in the received signal strength are more easily observed when water content in concrete is higher. Finally, we reconstructed a RSSI distribution map using computed tomography T2 - SMAR 2017 CY - Zurich, Switzerland DA - 13.09.2017 KW - RSSI KW - Concrete KW - Water KW - Monitoring KW - Computed Tomography PY - 2017 AN - OPUS4-43599 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kraft, Marco A1 - Würth, Christian A1 - Kaiser, Martin A1 - Muhr, V. A1 - Hirsch, T. A1 - Resch-Genger, Ute T1 - Particle size dependent optical properties of hexagonal β-NaYF4: 2 % Er3+, 20 % Yb3+ upconversion nanoparticles in cyclohexane and water N2 - Hexagonal NaYF4 doped with 20 % Yb3+ and 2 % Er3+ is an efficient upconversion (UC) phosphor for the conversion of 976 nm excitation light to emission at 845 nm, 800 nm, 655 nm, 540 nm and 410 nm light. The emission behavior of nanoparticles made from this material is strongly influenced by particle size, surface chemistry, and microenvironment. Furthermore their UC emission originates from multiphotonic absorption processes, rendering the resulting luminescence spectra and intensities excitation power density (P) dependent. Therefore the rational design of efficient nm-sized UC particles e.g., for applications in the material and life sciences requires reliable spectroscopic tools for the characterization of the optical properties of these materials like the excitation power density (P)-dependent UC quantum yield (QYUC) in dispersion, which presents a measure for the efficiency of the conversion of absorbed into emitted photons. Up to date the P-dependent absolute measurement of QYUC in aqueous media with an excitation wavelength of 976 nm presents a considerable challenge due to the low absorption coefficients of the UC materials and the absorption of water at this wavelength. T2 - International Conference on Advanced Materials and Nanotechnology CY - Queenstown, New Zealand DA - 12.02.2017 KW - Upconversion KW - Quantum yield KW - Lifetime KW - Water KW - Cyclohexane PY - 2017 AN - OPUS4-40093 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -