Measurement of Temperature Distribution Based on Optical Fiber-Sensing Technology and Tunable Diode Laser Absorption Spe...Published: 25 July 2018 by IntechOpen in Temperature Sensing
A method for localizing a fire source based on a distributed temperature sensor system is proposed. Two sections of optical fibers were placed orthogonally to each other as the sensing elements. A tray of alcohol was lit to act as a fire outbreak in a cabinet with an uneven ceiling to simulate a real scene of fire. Experiments were carried out to demonstrate the feasibility of the method. Rather large fluctuations and systematic errors with respect to predicting the exact room coordinates of the fire source caused by the uneven ceiling were observed. Two mathematical methods (smoothing recorded temperature curves and finding temperature peak positions) to improve the prediction accuracy are presented, and the experimental results indicate that the fluctuation ranges and systematic errors are significantly reduced. The proposed scheme is simple and appears reliable enough to locate a fire source in large spaces.
Improving the Resolution of 3D-Printed Molds for Microfluidics by Iterative Casting-Shrinkage CyclesPublished: 07 February 2017 by American Chemical Society (ACS) in Analytical Chemistry
Breaking through technical barriers and cost reduction are critical issues for the development of microfluidic devices, and both rely greatly on the innovation of fabrication techniques and use of new materials. The application of 3D printing definitely accelerated the prototyping of microfluidic chips by its versatility and functionality. However, the resolution of existing 3D printing techniques is still far below that of lithography, which makes it difficult to work on the scale of single cells and near impossible for single molecule work. In this paper, we present a facile way to increase the resolution of 3D printed microstructures to minimally 4 μm by casting-shrinkage cycles of a polyurethane (PU) polymer. A water-PU liquid mixture poured on a 3D printed template quickly solidifies replicating the structures, which then isometrically shrink to half its size after solvent evaporation, downscaling the replicated structures. By repeating the casting-shrinkage cycles, we could downscale the (sub)millimeter structures of 3D printed structures on demand, until the working limit posed by the polymer properties, which we demonstrate by fabricating a micromixer. Moreover, we can even fabricate microfluidic chips from millimeter-scale manually assembled templates, fully independent of any micromachining facilities, significantly reducing the technical barriers and costs, thus opening up the microfluidics field to low-resource areas.
Optical fiber Bragg grating (FBG) displacement sensors play an important role in various areas due to the high sensitivity to displacement. However, it becomes a serious problem of FBG cross-sensitivity of temperature and displacement in applications with FBG displacement sensing. This paper presents a method of temperature insensitive measurement of displacement via using an appropriate layout of the sensor. A displacement sensor is constructed with two FBGs mounted on the opposite surface of a cantilever beam. The wavelengths of the FBGs shift with a horizontal direction displacement acting on the cantilever beam. Displacement measurement can be achieved by demodulating the wavelengths difference of the two FBGs. In this case, the difference of the two FBGs’ wavelengths can be taken in order to compensate for the temperature effects. Four cantilever beams with different shapes are designed and the FBG strain distribution is quite different from each other. The deformation and strain distribution of cantilever beams are simulated by using finite element analysis, which is used to optimize the layout of the FBG displacement sensor. Experimental results show that an obvious increase in the sensitivity of this change on the displacement is obtained while temperature dependence greatly reduced. A change in the wavelength can be found with the increase of displacement from 0 to 10mm for a cantilever beam. The physical size of the FBG displacement sensor head can be adjusted to meet the need of different applications, such as structure health monitoring, smart material sensing, aerospace, etc. © (2016) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Fire Source Localization Based on Distributed Temperature Sensing by a Dual-Line Optical Fiber SystemPublished: 06 June 2016 by MDPI in Sensors
We propose a method for localizing a fire source using an optical fiber distributed temperature sensor system. A section of two parallel optical fibers employed as the sensing element is installed near the ceiling of a closed room in which the fire source is located. By measuring the temperature of hot air flows, the problem of three-dimensional fire source localization is transformed to two dimensions. The method of the source location is verified with experiments using burning alcohol as fire source, and it is demonstrated that the method represents a robust and reliable technique for localizing a fire source also for long sensing ranges.
Study on spatial resolution improvement of distributed temperature sensor system by linear fitting algorithmPublished: 08 October 2015 by SPIE-Intl Soc Optical Eng in AOPC 2015: Optical Fiber Sensors and Applications
Spatial resolution determines the minimum space unit that a distributed temperature sensor system can distinguish along the fiber thus it is an important parameter to evaluate the performance of the distributed temperature sensor system. A typical distributed temperature sensor system with a spatial resolution of 5m is built and an algorithm of linear fitting correction is proposed to realize temperature measurement of fiber length shorter than 5m accurately. With the method of linear fitting correction, the spatial resolution of the distributed temperature sensor system has been improved from 5m to 1m. The measured temperature of the DTS system is well calibrated by using linear fitting correction algorithm with a fiber length of 4m, 3m, 2m and 1m respectively. The maximum error of the corrective temperature is 2℃ for long term measurement.
Temperature calibration of optical fiber attenuation differences induced measurement error of Raman distributed temperat...Published: 28 September 2015 by SPIE-Intl Soc Optical Eng in 24th International Conference on Optical Fibre Sensors
The effect of optical fiber attenuation differences (AD) induced temperature error of Raman distributed temperature sensor (RDTS) is analyzed using the temperature demodulation algorithm. First of all, a novel method to address the effects caused by the AD between Stokes and anti-Stokes light is proposed. Furthermore, the temperature measurement error caused by additional AD of fiber temperature is also reduced by using a formula obtained by experimental data. The experimental results demonstrate that the RDTS system can measure different temperature zones more accurately.
The process of molecules translocation through nanopore is important to understand many interesting phenomena. Molecular dynamics simulations have been carried out to study the translocation of alkane through graphene nanopore. The results detail relative distance, average translation time, etc. The translocation process can be divided into three stages: finding-entering-moving through the nanopore. Alkane must climb an energy barrier in every stage. The dependence of translocation on chain length is also discussed. Shorter alkanes are easy to transport through the nanopore and the average translocation time is short when alkane translocates through nanopore one by one. Our simulations show a visualized translocation process, which can favor our understanding of this important process.
Molecular dynamics simulation on the effect of the distance between SWCNTs for short polymers diffusion among single wal...Published: 01 December 2014 by Elsevier BV in Computational Materials Science
Molecular dynamics simulation of isothermal crystallisation of polymer chains around single polymer lamellaPublished: 27 September 2013 by Informa UK Limited in Molecular Simulation
The isothermal crystallisation of polyethylene (PE) chains around single PE lamella in vacuum is investigated by molecular dynamic simulation. The crystallisation process is analysed in terms of the orientational order parameters, principal moments of inertia for the simulated systems. The effects of charge interactions between the polymer chains and lamella are discussed. It is found that the crystallisation process for uncharged systems can be divided into three stages: (1) adsorption, (2) orientation and (3) arrangement. The single polymer lamella changes a little during the three stages. PE chains are arranged parallel to the chain direction of the stems in the crystalline state. When considering the effect of charge interactions between the polymer chains and lamella, a different crystallisation process appears. The single polymer lamella is affected by the charged polymer chains.
Predicting glass transition temperature of polyethylene/graphene nanocomposites by molecular dynamic simulationPublished: 24 May 2013 by Springer Nature in Chemical Research in Chinese Universities
The glass transition temperature of polyethylene/graphene nanocomposites was investigated by molecular dynamic simulation. The specific volumes of three systems(polyethylene, polyethylene with a small graphene sheet and two small graphene sheets) were examined as a function of temperature. We found that the glass transition temperature decreases with increasing graphene. Then the van der Waals energy changes obviously with increasing graphene and the torsion energy also plays an important role in the glass transition of polymer. The radial distribution functions of the inter-molecular carbon atoms suggest the interaction between PE and graphene weakens with increasing graphene. These indicate that graphene can prompt the motion of chain segments of polymer and decrease the glass transition temperature (T g) of polymer.