TY - CONF
A1 - Lu, Xin
T1 - Introduction to group 8.6
N2 - A brief introduction of group 8.6 and the research work on the application of fiber sensing.
T2 - DIU Besuch
CY - Berlin, Germany
DA - 05.05.2023
KW - Structural health monitoring
KW - Distributed fiber sensing
KW - Distributed acoustic sensing
KW - Practical application
PY - 2023
AN - OPUS4-57430
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Davison, Nathan
A1 - Hemingway, Jack M.
A1 - Wills, Corinne
A1 - Stolar, Tomislav
A1 - Waddell, Paul G.
A1 - Dixon, Casey M.
A1 - Barron, Luke
A1 - Dawson, James A.
A1 - Lu, Erli
T1 - Mechanochemical Synthesis of a Sodium Anion Complex [Na+(2,2,2-cryptand)Na–] and Studies of Its Reactivity: Two-Electron and One-Electron Reductions
N2 - Group 1 metal molecular chemistry is dominated by a +1 oxidation state, while a 0 oxidation state is widespread in the metals. A more exotic, yet still available, oxidation state of group 1 metal is −1, i.e., alkalide. Reported as early as the 1970s, the alkalides appear in every modern inorganic chemistry textbook as an iconic chemical curiosity, yet their reactivity remains unexplored. This is due to their synthetic hurdles. In this work, we report the first facile synthesis of the archetypical alkalide complex, [Na+(2,2,2-cryptand)Na–], which allows us to unveil a versatile reactivity profile of this once exotic species.
KW - Mechanochemistry
PY - 2024
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-608632
DO - https://doi.org/10.1021/acs.inorgchem.4c02914
VL - 63
IS - 32
SP - 15247
EP - 15258
PB - American Chemical Society (ACS)
AN - OPUS4-60863
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Hellemans, S.
A1 - Rocha, M. M.
A1 - Wang, M.
A1 - Romero Arias, J.
A1 - Aanen, D. K.
A1 - Bagnères, A.-G.
A1 - Buček, A.
A1 - Carrijo, T. F.
A1 - Chouvenc, T.
A1 - Cuezzo, C.
A1 - Constantini, J. P.
A1 - Constantino, R.
A1 - Dedeine, F.
A1 - Deligne, J.
A1 - Eggleton, P.
A1 - Evans, T. A.
A1 - Hanus, R.
A1 - Harrison, Mark C.
A1 - Harry, M.
A1 - Josens, G.
A1 - Jouault, C.
A1 - Kalleshwaraswamy, C. M.
A1 - Kaymak, E.
A1 - Korb, J.
A1 - Lee, C.-Y.
A1 - Legendre, F.
A1 - Li, H.-F.
A1 - Lo, N.
A1 - Lu, T.
A1 - Matsuura, K.
A1 - Maekawa, K.
A1 - McMahon, Dino Peter
A1 - Mizumoto, N.
A1 - Oliveira, D. E.
A1 - Poulsen, M.
A1 - Sillam-Dussès, D.
A1 - Su, N.-Y.
A1 - Tokuda, G.
A1 - Vargo, E. L.
A1 - Ware, J. L.
A1 - Šobotník, J.
A1 - Scheffrahn, R. H.
A1 - Cancello, E.
A1 - Roisin, Y.
A1 - Engel, M. S.
A1 - Bourguignon, T.
T1 - Genomic data provide insights into the classification of extant termites
N2 - The higher classification of termites requires substantial revision as the Neoisoptera, the most diverse termite lineage, comprise many paraphyletic and polyphyletic higher taxa. Here, we produce an updated termite classification using genomic-scale analyses. We reconstruct phylogenies under diverse substitution models with ultraconserved elements analyzed as concatenated matrices or within the multi-species coalescence framework. Our classification is further supported by analyses controlling for rogue loci and taxa, and topological tests. We show that the Neoisoptera are composed of seven family-level monophyletic lineages, including the Heterotermitidae Froggatt, Psammotermitidae Holmgren, and Termitogetonidae Holmgren, raised from subfamilial rank. The species-rich Termitidae are composed of 18 subfamily-level monophyletic lineages, including the new subfamilies Crepititermitinae, Cylindrotermitinae, Forficulitermitinae, Neocapritermitinae, Protohamitermitinae, and Promirotermitinae; and the revived Amitermitinae Kemner, Microcerotermitinae Holmgren, and Mirocapritermitinae Kemner. Building an updated taxonomic classification on the foundation of unambiguously supported monophyletic lineages makes it highly resilient to potential destabilization caused by the future availability of novel phylogenetic markers and methods. The taxonomic stability is further guaranteed by the modularity of the new termite classification, designed to accommodate as-yet undescribed species with uncertain affinities to the herein delimited monophyletic lineages in the form of new families or subfamilies.
KW - Termite
KW - Taxonomy
KW - Evolution
PY - 2024
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-608276
DO - https://doi.org/10.1038/s41467-024-51028-y
VL - 15
IS - 1
SP - 1
EP - 17
PB - Springer Science and Business Media LLC
AN - OPUS4-60827
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Lu, Xin
A1 - Krebber, Katerina
T1 - Configuration simplification and data reduction in a DAS system for monitoring large infrastructures
N2 - The distributed acoustic sensor based on an imbalanced Mach-Zehnder interferometer with a 3×3 coupler is simplified by using a balanced detector instead of three identical photodetectors. The obtained data is reduced by two third accordingly.
T2 - Optica Sensing Congress 2024
CY - Toulouse, France
DA - 15.07.2024
KW - Data reduction
KW - Distributed fiber optic sensing
KW - System simplification
PY - 2024
SP - 1
EP - 2
PB - Optica
CY - Washington D.C., USA
AN - OPUS4-60840
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Lu, Xin
T1 - Configuration simplification and data reduction in a DAS system for monitoring large infrastructures
N2 - The distributed acoustic sensor based on an imbalanced Mach-Zehnder interferometer with a 3×3 coupler is simplified by using a balanced detector instead of three identical photodetectors. The obtained data is reduced by two third accordingly.
T2 - Optica Sensing Congress 2024
CY - Toulouse, France
DA - 15.07.2024
KW - Distributed fiber sensing
KW - System simplification
KW - Data reduction
PY - 2024
AN - OPUS4-60841
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Hicke, Konstantin
A1 - Lu, Xin
A1 - Chruscicki, Sebastian
A1 - Krebber, Katerina
T1 - Measurement of Slowly Changing and Quasi-Static Strain Signals for Ground Motion Monitoring Applications using Distributed Acoustic Sensing
N2 - The suitability of wavelength-scanning COTDR for distributed dynamic strain sensing (DAS) along buried fiber cables for long-term geotechnical monitoring applications is demonstrated by experiments showing the method’s capability to demodulate slowly varying and quasi-static signals.
T2 - Optica Sensing Congress 2024
CY - Toulouse, France
DA - 15.07.2024
KW - Ground motion
KW - Ground movement monitoring
KW - Distributed fiber optic sensing
KW - Quasi-static signals
KW - Geomonitoring
PY - 2024
SP - 1
EP - 2
PB - Optica
CY - Washington D.C., USA
AN - OPUS4-60816
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Lu, Xin
A1 - Krebber, Katerina
T1 - Suppression of Rayleigh fading induced errors in φOTDR by different pulse widths for improving the reliability of civil infrastructure monitoring
N2 - Rayleigh fading is a widely observed phenomenon in the many fields, such as wireless communication and optical imaging. It is also the main factor limiting the performance of the phase-sensitive optical time domain reflectometry (φOTDR). The low SNR at the fading points results in a large measurement error, severely affecting the reliability of civil infrastructure monitoring. The proposed method involves changing the pulse width during measurements to suppress the impact of fading. Experimental result shows that the number of fading points is greatly reduced by ∼ 96 % and the measurement error is reduced by more than 5 times. Unlike existing methods, this approach requires no hardware modifications, making it applicable to almost all current phase-based φOTDR systems. The versatility and effectiveness of this method make it an excellent candidate for infrastructure monitoring and related fields.
KW - Distributed fiber sensing
KW - Optical fiber sensing
KW - Phase-sensitive optical time domain reflectometry
KW - Infrastructure monitoring
KW - Rayleigh fading
PY - 2025
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-614208
DO - https://doi.org/10.1016/j.optlastec.2024.111927
SN - 1879-2545
VL - 181
SP - 1
EP - 9
PB - Elsevier Ltd.
AN - OPUS4-61420
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Lu, Xin
A1 - Hicke, Konstantin
A1 - Krebber, Katerina
T1 - Distributed fiber optic sensing for monitoring of underground facilities
N2 - Distributed fiber optic sensing (DFOS) technique is a promising and robust non-destructive testing tool that can seamlessly acquire environmental conditions over large scales. Therefore, it has found extensive applications in structural health monitoring. Its appeal for monitoring underground facilities lies in the intrinsic properties of the optical fiber, such as immunity to magnetic interference, small size, chemical inertia, etc. This paper provides a concise overview of DFOS applications in underground facility monitoring. Following a brief introduction to the working principle of the DFOS technique, various examples are provided to demonstrate how distributed fiber sensors contribute to monitoring underground facilities. The paper presents unpublished field test results with an emphasis in the energy sector, including monitoring gas storage facilities, geothermal reservoir exploration, and ground movement detection. Furthermore, the paper identifies several directions for enhancing the DFOS system.
T2 - SPIE Photonics Europe
CY - Strasbourg, France
DA - 07.04.2024
KW - Underground gas storage
KW - Distributed fiber sensing
KW - Geothermal borehole
KW - Ground movement
KW - Leakage detection
KW - Structure health monitoring
PY - 2024
AN - OPUS4-60146
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Lu, Xin
A1 - Hicke, Konstantin
A1 - Krebber, Katerina
T1 - Distributed fiber optic sensing for monitoring of underground facilities
N2 - Distributed fiber optic sensing (DFOS) technique is a promising and robust non-destructive testing tool that can seamlessly acquire environmental conditions over large scales. Therefore, it has found extensive applications in structural health monitoring. Its appeal for monitoring underground facilities lies in the intrinsic properties of the optical fiber, such as immunity to magnetic interference, small size, chemical inertia, etc. This paper provides a concise overview of DFOS applications in underground facility monitoring. Following a brief introduction to the workingbnprinciple of the DFOS technique, various examples are provided to demonstrate how distributed fiber sensors contribute to monitoring underground facilities. The paper presents unpublished field test results with an emphasis in the energy sector, including monitoring gas storage facilities, geothermal reservoir exploration, and ground movement detection. Furthermore, the paper identifies several directions for enhancing the DFOS system.
T2 - SPIE Photonics Europe
CY - Strasbourg, France
DA - 07.04.2024
KW - Structure health monitoring
KW - Geothermal borehole
KW - Distributed fiber optic sensing
KW - Ground movement
KW - Leakage detection
PY - 2024
DO - https://doi.org/10.1117/12.3023571
SN - 0277-786X
VL - 13001
SP - 1
EP - 10
PB - SPIE
AN - OPUS4-60384
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Huang,
A1 - Zheng,
A1 - Zhang,
A1 - Lu,
A1 - Wang,
A1 - Kunte, Hans-Jörg
A1 - Sand, W.
T1 - Long Term Temperature and Humidity Evolution Forecast in Near Field of Nuclear Waste Container
N2 - The paper aims to simulate the corrosion environment of nuclear waste containers at different geological disposal periods to obtain temperature and humidity information at the interface between the container and the surrounding environment. The simulated data and calculation results of long term temperature evolution at the surface of nuclear waste (HLW) containers from some typical nuclear countries about the safety disposition were reviewed. Combining different burial patterns, this paper speculated the long term temperature evolution rule for China. According to the study about saturation variation of buffer/backfill material at home and abroad, the humidity evolution of bentonite at the surface of HLW containers was specu- lated. The study showed that the temperature of the container surface increased rapidly at the beginning, and gradually decreased after the climax. For safety reasons, the maximum temperature was designed below 100°C. The saturation of bentonite was af- fected by the mutual influences of the heat released by nuclear waste decay and the infiltration of groundwater. It was dominated by the released heat in the early stage, and later was influenced greatly by the infiltration of groundwater. It is generally believed that the water content at the surface of the container will increase obviously in about 3 years, and will be saturated in about 10 years. The prediction of long-term temperature and humidity evolution will lay a foundation for study of corrosion evolution of nuclear waste containers in China.
KW - Corrosion evolution
KW - Nuclear waste
KW - Disposal repository
KW - Temperature and humidity
PY - 2018
SN - 1672-9242
VL - 15
IS - 10
SP - 109
EP - 113
PB - Zhongguo Bingqi Gongye di-wujiu Yanjiusuo
CY - Chongqing
AN - OPUS4-46953
LA - zho
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Huang, Y.-L.
A1 - Zheng,
A1 - Zhang,
A1 - Lu,
A1 - Wang,
A1 - Kunte, Hans-Jörg
A1 - Sand, W.
T1 - Forecast on Long Term Chemical Environment Evolution on Surface of Nuclear Waste Container
N2 - Surface environment changes of nuclear waste container, mainly including oxygen contents, buffer pore water components and pH under the conditions of “borehole” type and “In-floor” type with bentonite buffer/backfill and concrete buffer were summarized. This summarization provides a basic corrosion environment reference for the corrosion evolution re- search of high-level radioactive waste disposal repository in our country.
KW - Corrosion evolution
KW - Nuclear waste
KW - Disposal repository
KW - Corrosion environment
PY - 2018
DO - https://doi.org/10.7643/ issn.1672-9242.2018.10.017
SN - 1672-9242
VL - 15
IS - 10
SP - 103
EP - 108
PB - Zhongguo Bingqi Gongye di-wujiu Yanjiusuo
CY - Chongqing
AN - OPUS4-46952
LA - zho
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Christensen, J. B.
A1 - Jørgensen, A. A.
A1 - Vandborg, M. H.
A1 - Thomas, P. J.
A1 - Lu, Xin
A1 - Failleau, G.
A1 - Eisermann, R.
A1 - Grüner-Nielsen, L.
A1 - Balslev-Harder, D.
A1 - Lassen, M.
A1 - Krenek, S.
T1 - Fiber-artefact methodology and calibration framework for Brillouin-based fiber sensing
N2 - We propose, and demonstrate, the use of a fiber-optical measurement artefact as a metrological tool for traceable distance calibration of distributed optical fiber sensors. The constructed fiber artefact consists of a lead-in fiber coupled to a fiber loop using a 3-dB coupler and is used to calibrate both a home-build Brillouin-OTDR setup and a custom version of a commercial Brillouin-OTDR interrogator build for distributed temperature sensing. For both interrogators, we demonstrate distance calibrations with 1-meter uncertainty (k=1) in the offset length and 0.1 % (1 m/km) uncertainty (k = 1) in the distance scale factor. In addition, it is shown that the fiber artefact can be used to assess undesired distance-dependent measurement biases.
KW - Distributed temperature sensing
KW - Metrology
KW - Distributed optical fiber sensing
KW - Brillouin optical time-domain reflectrometry
PY - 2024
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-618853
DO - https://doi.org/10.1364/OE.544659
SN - 1094-4087
VL - 32
IS - 26
SP - 45483
EP - 45493
PB - Optica Publishing Group
AN - OPUS4-61885
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Lu, Xin
T1 - Progress review
N2 - We report on the progress on calibration and characterization of distributed temperature sensing systems as a part of the European INFOTherm project. The most research results were achieved in the framework of the Work Package 2.
T2 - Midterm meeting of INFOTherm project
CY - Copenhagen, Denmark
DA - 25.03.2025
KW - Humidity sensor
KW - Optical fibre sensors
KW - Distributed temperature sensing
PY - 2025
AN - OPUS4-63007
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Lu, Xin
A1 - Hicke, Konstantin
A1 - Breithaupt, Mathias
A1 - Strangfeld, Christoph
T1 - Distributed Humidity Sensing in Concrete Based on Polymer Optical Fiber
N2 - We present a preliminary investigation on distributed humidity monitoring during the drying process of concrete based on an embedded polymer optical fiber (POF). The water dissipated into the POF changes several properties of the fiber such as refractive index, scattering coefficient and attenuation factor, which eventually alters the Rayleigh backscattered light. The optical time Domain reflectometer (OTDR) technique is performed to acquire the backscattered signal at the wavelengths 650 nm and 500 nm, respectively. Experimental results show that the received signal increases at 650 nm while the fiber attenuation factor clearly increases at 500 nm, as the concrete dries out. In the hygroscopic range, the information retrieved from the signal change at 650 nm agrees well with the measurement result of the electrical humidity sensors also embedded in the concrete sample.
KW - Distributed fiber optic sensing
KW - Distributed humidity sensing
KW - Polymer optical fibers
KW - Concrete drying
KW - Material moisture
KW - Embedded humidity sensors
PY - 2021
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-537644
DO - https://doi.org/10.3390/polym13213755
SN - 2073-4360
VL - 13
IS - 21
SP - 3755
PB - MDPI
CY - Basel, Switzerland
AN - OPUS4-53764
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Hu, W.
A1 - Said, Samir
A1 - Rohrmann, R.
A1 - Teng, J.
A1 - Li, Z.
A1 - Lu, W.
A1 - Cunha, A.
T1 - Operational modal analysis and continuous dynamic monitoring of structures
N2 - This paper addresses operational modal analysis (OMA) and continuous dynamic monitoring (CDM) of two bridges. One of them is installed with Tuned Mass Dampers (TMDs) while another one is a normal bridge. Two ambient vibration tests were performed on these two bridges respectively. It is observed that not only installation of TMDs but also environmental factors influence the variations of structural frequencies, which may mask the subtle change induced by small structural changes. As a result, continuous dynamic monitoring systems were implemented on these two bridges, in order to evaluate efficiency of the TMD system, remove the environmental effects and build reliable damage indices that are only sensitive to structural changes. The results of CDM of these two bridges during several years are presented. Software systems developed for OMA and CDM are also introduced.
T2 - 14th International Symposium on Structural Engineering (ISSE-14)
CY - Beijing, Peoples Republic of China
DA - 12.10.2016
KW - Structure
KW - Operational modal analysis
KW - Continuous dynamic monitoring
PY - 2016
SN - 978-7-03-050125-7
VL - 2016
SP - 366
EP - 372
PB - Science Press Beijing
AN - OPUS4-38876
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Qiu, Q.
A1 - Noll, Matthias
A1 - Abraham, W.-R.
A1 - Lu, Y.
A1 - Conrad, R.
T1 - Applying stable isotope probing of phospholipid fatty acids and rRNA in a Chinese rice field to study activity and composition of the methanotrophic bacterial communities in situ
N2 - Methanotrophs in the rhizosphere play an important role in global climate change since they attenuate methane emission from rice field ecosystems into the atmosphere. Most of the CH4 is emitted via transport through the plant gas vascular system. We used this transport for stable isotope probing (SIP) of the methanotrophs in the rhizosphere under field conditions and pulse-labelled rice plants in a Chinese rice field with CH4 (99% 13C) for 7 days. The rate of 13CH4 loss rate during 13C application was comparable to the CH4 oxidation rate measured by the difluoromethane inhibition technique. The methanotrophic communities on the roots and in the rhizospheric soil were analyzed by terminal-restriction fragment length polymorphism (T-RFLP), cloning and sequencing of the particulate methane monooxygenase (pmoA) gene. Populations of type I methanotrophs were larger than those of type II. Both methane oxidation rates and composition of methanotrophic communities suggested that there was little difference between urea-fertilized and unfertilized fields. SIP of phospholipid fatty acids (PLFA-SIP) and rRNA (RNA-SIP) were used to analyze the metabolically active methanotrophic community in rhizospheric soil. PLFA of type I compared with type II methanotrophs was labelled more strongly with 13C, reaching a maximum of 6.8 atom-% . T-RFLP analysis and cloning/sequencing of 16S rRNA genes showed that methanotrophs, especially of type I, were slightly enriched in the 'heavy' fractions. Our results indicate that CH4 oxidation in the rice rhizosphere under in situ conditions is mainly due to type I methanotrophs.
KW - Methane-oxidizing bacteria
KW - Rice field
KW - Rhizosphere
KW - Stable isotope probing
KW - Phospholipid fatty acid
KW - Particulate methane monooxygenase
PY - 2008
DO - https://doi.org/10.1038/ismej.2008.34
SN - 1751-7362
SN - 1751-7370
IS - 2
SP - 602
EP - 614
PB - Nature Publishing Group
CY - Basingstoke
AN - OPUS4-17660
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Lu, P.
A1 - Lannutti, J.J.
A1 - Klobes, Peter
A1 - Meyer, Klaus
T1 - X-ray Computed Tomography and Mercury Porosimetry for Evaluation of Density Evolution and Porosity Distribution
N2 - X-ray computed tomography (CT) and mercury porosimetry were combined to connect density gradients and the distribution of open porosity in a sintered compact. CT clearly showed that open porosity follows the initial distribution of low-density zones. Mercury porosimetry detected three distinct levels of porosity. Microstructural examination correlated the porosity level with the coordination of (i) two to three or (ii) multiple grains around pores. This combination of techniques provides a novel tool for the study of pore and density-gradient evolution during sintering.
PY - 2000
DO - https://doi.org/10.1111/j.1151-2916.2000.tb01227.x
SN - 0002-7820
SN - 1551-2916
VL - 83
IS - 3
SP - 518
EP - 522
PB - Blackwell Publishing
CY - Malden
AN - OPUS4-11955
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Bothe, Martin
A1 - Mya, K.Y.
A1 - Lin, E.M.J.
A1 - Yeo, C. C.
A1 - Lu, X.
A1 - He, C.
A1 - Pretsch, Thorsten
T1 - Triple-shape properties of star-shaped POSS-polycaprolactone polyurethane networks
N2 - Here, we present an investigation of the triple-shape properties of star-shaped polyhedral oligomeric silsesquioxane-poly(ε-caprolactone) polyurethanes (SPOSS-PUs), which have three-dimensional network structures. In a typical 'triple-shape functionalization process', mostly consisting of two tensile deformations at different temperatures, chain immobilization of the polymer network component poly(ε-caprolactone) (PCL) was successfully realized first through crystallization and then through vitrification. Subsequently, large parts of the respective strains were released under stress-free recovery conditions. The two-fold fixed ('programmed') specimens responded to heating with two independent length contractions (switching steps); the first shape change was associated with PCL devitrification and the second one with the melting of hitherto crystalline PCL. It was revealed that the triple-shape properties of SPOSS-PU networks considerably depend on PCL network chain length. When applying exactly the same 'triple-shape creation procedure', larger strain releases were detected in the first transition for polymers with a higher PCL network chain length, whereas the second transition was more accentuated for SPOSS-PU networks with a shorter PCL chain length. In the course of thermo-mechanical cycling, the formation of a neck during the second tensile deformation was repeatedly detected for SPOSS-PUs with higher PCL network chain length; in the subsequent recovery process the specimens even exhibited the highest total strain recoverability. Finally, gradual strain release could be achieved at temperatures below the PCL melting transition through the selection of up to four temperature holding steps, at which every time stable shapes were formed.
KW - Shape memory polymer
KW - Active polymer
KW - Triple-shape polymer
KW - Hybrid star-shaped polymer
KW - POSS-polycaprolactone polyurethanes
KW - Thermo-mechanical properties
PY - 2012
DO - https://doi.org/10.1039/c1sm06474f
SN - 1744-683X
VL - 8
IS - 4
SP - 965
EP - 972
PB - RSC Publ.
CY - Cambridge
AN - OPUS4-25260
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Lu, Xin
T1 - Humidity response analysis of optical fibers with hygroscopic coatings based on Lamé’s equations
N2 - Optical fibers with hygroscopic coatings are widely used for humidity sensing, where the coating expands upon absorbing water, inducing strain in the fiber. This strain is then used to determine humidity. However, previous studies have oversimplified the strain generation process. A comprehensive three-dimensional model of the mechanical interaction between the coating and the fiber is built based on Lamé’s equations. An analytical expression for the induced strain is derived. The proposed model predicts larger humidity-induced strain compared to the reported ones, given the same Young’s modulus or coefficient of humidity expansion for the coating. Interestingly, the effect of coating thickness on strain response are quite similar for both methods. Experimental validation using fibers with a polyimide coating shows strong agreement with the theoretical predictions.
T2 - 29th International Conference on Optical Fiber Sensors
CY - Porto, Portugal
DA - 26.05.2025
KW - Distributed fiber sensing
KW - Humidity sensors
KW - Lamé’s equations
KW - Reflectometry
KW - Optical fiber sensors
KW - Rayleigh scattering
KW - Structural health monitoring
PY - 2025
AN - OPUS4-63261
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Lu, Xin
T1 - Polarization diversity detection based wavelength scanning coherent optical time domain reflectometry
N2 - Although wavelength scanning coherent optical time-domain reflectometry (WS-COTDR) system is immune to fading effect, it suffers from occasional and localized large errors caused by the false peak in the correlation spectrum due to the large signal generated in the random interference of the backscattered light. Polarization diversity detection is applied to a standard WS-COTDR system to suppress large measurement errors. In this way, the orthogonally polarized components of backscattered light can be obtained and processed separately. Due to the birefringence of the sensing fiber, the components experience different interference processes, so the average of their correlation spectrum can suppress the false peaks and finally reduce the occurrence of larger errors. The effectiveness of the proposed method is validated in laboratory for monitoring of sinusoidal vibrations and in field for tracking the bus movement via a dark fiber.
T2 - 29th International Conference on Optical Fiber Sensors
CY - Porto, Portugal
DA - 26.05.2025
KW - Coherent optical time domain reflectometry
KW - Traffic monitoring
KW - Polarization diversity detection
KW - Distributed fiber sensing
PY - 2025
AN - OPUS4-63260
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Lu, Xin
A1 - Schukar, Marcus
A1 - Großwig, S.
A1 - Weber, U.
A1 - Krebber, Katerina
T1 - Monitoring acoustic events in boreholes using wavelengthscanning coherent optical time domain reflectometry in multimode fiber
N2 - A distributed acoustic sensor (DAS) based on wavelength-scanning coherent optical time domain reflectometer (WS-COTDR) is tested in an underground gas storage based on a multimode fiber for the first time to the best of our knowledge. The WS-COTDR acquires the reflection spectrum by scanning the wavelength of the laser and uses the spectra to calibrate strain. It overcomes the fading problem which is common for all DAS systems, and possesses the advantage of simple configuration and low-cost. The working principle of the system is well explained and the measurement results are presented. Various artificial and natural acoustic events have been successfully detected by the WS-COTDR. Such a sensor demonstrates several advantages over the traditional DAS systems, so it is supposed to be widely used in the oil and gas industry.
T2 - EAGE GeoTech 2021 Second EAGE Workshop on Distributed Fibre Optic Sensing
CY - Online meeting
DA - 01.03.2021
KW - Leakage detection
KW - Distributed acoustic sensing
KW - Distributed fiber optic sensing
PY - 2021
DO - https://doi.org/10.3997/2214-4609.202131010
SP - Paper 10, 1
PB - European Association of Geoscientists & Engineers
CY - Houten, Niederlande
AN - OPUS4-52248
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Lu, Xin
A1 - Schukar, Marcus
A1 - Großwig, S.
A1 - Weber, U.
A1 - Krebber, Katerina
T1 - Monitoring acoustic events in boreholes using wavelengthscanning coherent optical time domain reflectometry in multimode fiber
N2 - A distributed acoustic sensor (DAS) based on wavelength-scanning coherent optical time domain reflectometer (WS-COTDR) is tested in an underground gas storage based on a multimode fiber for the first time to the best of our knowledge. The WS-COTDR acquires the reflection spectrum by scanning the wavelength of the laser and uses the spectra to calibrate strain. It overcomes the fading problem which is common for all DAS systems, and possesses the advantage of simple configuration and low-cost. The working principle of the system is well explained and the measurement results are presented. Various artificial and natural acoustic events have been successfully detected by the WS-COTDR. Such a sensor demonstrates several advantages over the traditional DAS systems, so it is supposed to be widely used in the oil and gas industry.
T2 - EAGE GeoTech 2021
CY - Online meeting
DA - 01.03.2021
KW - Borehole monitoring
KW - Distributed fiber sensing
KW - Acoustic sensing
PY - 2021
DO - https://doi.org/10.3997/2214-4609.202131010
SP - 1
EP - 5
AN - OPUS4-52152
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -