Polymers beyond standard optical fibres – fabrication of microstructured polymer optical fibres

This paper reports the overall fabrication process of microstructured polymer optical fibres (mPOFs). mPOF fabrication involves a two‐step process: on the one hand, the design and creation of a preform containing a large‐scale version of the desired fibre and, on the other, the precise heating and drawing of the preform to the final fibre. The preforms are produced either by an improved drilling technique or by capillary stacking. For a correct and accurate drawing of the fibre, a controlled and precise heating unit has to be designed, an issue that will be explained in detail in this work. The quality and optical performance of the final mPOF depends strongly on key factors such as the preform annealing, the accuracy of the technique selected for the creation of the preform structure, the heating stage, as well as on the drawing parameters. All of them are analysed in detail and some drawn mPOFs of interest are reported as well. © 2018 Society of Chemical Industry     

Automatic on-line monitoring of atmospheric volatile organic compounds: gas chromatography-mass spectrometry and gas chromatography-flame ionization detection as complementary systems

Traditionally air quality networks have been carrying out the continuous, on-line measurement of volatile organic compounds (VOC) in ambient air with GC-FID. In this paper some identification and coelution problems observed while using this technique in long-term measurement campaigns are described. In order to solve these problems a GC-MS was set up and operated simultaneously with a GC-FID for C₂-C₁₁ VOCs measurement.There are few on-line, unattended, long term measurements of atmospheric VOCs performed with GC-MS. In this work such a system has been optimized for that purpose, achieving good repeatability, linearity, and detection limits of the order of the GC-FID ones, even smaller in some cases. VOC quantification has been made by using response factors, which is not frequent in on-line GC-MS. That way, the identification and coelution problems detected in the GC-FID, which may led to reporting erroneous data, could be corrected.The combination of GC-FID and GC-MS as complementary techniques for the measurement of speciated VOCs in ambient air at sub-ppbv levels is proposed. Some results of the measurements are presented, including concentration values for some compounds not found until now on public ambient air VOC databases, which were identified and quantified combining both techniques. Results may also help to correct previously published VOC data with wrongly identified compounds by reprocessing raw chromatographic data.     

Cover Image,Volume 67, Issue 9

The cover image, by Eneko Arrospide et al., is based on the Review Polymers beyond standard optical fibres ‐ fabrication of microstructured polymer optical fibres, DOI: 10.1002/pi.5602 .

     

Cubical Mass-Spring Model design based on a tensile deformation test and nonlinear material model

Mass-Spring Models (MSMs) are used to simulate the mechanical behavior of deformable bodies such as soft tissues in medical applications. Although they are fast to compute, they lack accuracy and their design remains still a great challenge. The major difficulties in building realistic MSMs lie on the spring stiffness estimation and the topology identification. In this work, the mechanical behavior of MSMs under tensile loads is analyzed before studying the spring stiffness estimation. In particular, the performed qualitative and quantitative analysis of the behavior of cubical MSMs shows that they have a nonlinear response similar to hyperelastic material models. According to this behavior, a new method for spring stiffness estimation valid for linear and nonlinear material models is proposed. This method adjusts the stress-strain and compressibility curves to a given reference behavior. The accuracy of the MSMs designed with this method is tested taking as reference some soft-tissue simulations based on nonlinear Finite Element Method (FEM). The obtained results show that MSMs can be designed to realistically model the behavior of hyperelastic materials such as soft tissues and can become an interesting alternative to other approaches such as nonlinear FEM.     

New method to calculate mode conversion coefficients in SI multimode optical fibers

A simple method is proposed for the experimental calculation of the mode conversion coefficients in multimode optical fibers. It only requires observing the far-field output pattern from a fixed length of fiber as the launching angle changes, as well as the intersection point between two far-field output patterns corresponding to two different input angles. The results obtained with this method are quite insensitive to small variations of the experimental parameters. A good agreement between theoretical and experimental results is also found.     

Analysis of a plastic optical fiber-based displacement sensor

An easy-to-manufacture setup for a displacement sensor based on plastic optical fiber (POF) is analyzed, showing computational and experimental results. If the displacement is the consequence of force or pressure applied to the device, this can be used as a force or pressure transducer. Its principle of operation consists of bending a POF section around a flexible cylinder and measuring light attenuation when the whole set is subjected to side pressure. Attenuations are obtained computationally as a function of side deformation for different design parameters. Experimental results with an actually built prototype are also provided.     

TeknoAssistant : a domain specific tech mining approach for technical problem-solving support

Scientometrics - This paper presents TeknoAssistant, a domain-specific tech mining method for building a problem–solution conceptual network aimed at helping technicians from a particular...     

Evolution of amino acids and biogenic amines in natural ciders as a function of the year and the manufacture steps

The evolution of biogenic amines and other nitrogen compounds during the elaboration period of natural ciders in two successive seasons and two types of presses was studied. The harvest year affects the concentrations of most of the amino acids, while few of them were affected by the type of press. Asparagine and aspartic acid were the most abundant amino acids in fresh musts followed by α‐alanine, α‐aminobutyric acid, glutamine and glutamic acid. The mean concentrations of these amino acids in the fresh musts from the two harvest years were 12.35, 11.12, 6.45, 6.29, 5.28 and 4.87 mg L^?1, respectively. During cidermaking, a decrease in the sum of all amino acids was detected (from 128 ± 54.311 mg L^?1 to 22.5 ± 4.863 mg L^?1 in 2005 and from 72.2 ± 15.256 mg L^?1 to 6.5 ± 4.112 mg L^?1 in 2006). Furthermore, significant differences in the concentration of most amino acids related to harvest year were observed. Concerning the biogenic amine content, putrescine was the main and the only amine present in all musts (3.72 ± 1.68 mg L^?1) and ciders (3.59 ± 1.83 mg L^?1). Histamine was the second biogenic amine of quantitative importance in final ciders (1.15 ± 0.69 mg L^?1), and tyramine was only detected in one of the cidermaker cellars at the end of the elaboration period. The low concentrations of biogenic amines in ciders were attributed to the low contents of the corresponding precursor amino acids and do not affect to cider quality.     

Parameters affecting bending losses in graded-index polymer opticalfibers

Radiation losses that occur when bending graded-index polymer optical fibers (POFs) are analyzed as a function of the profile exponent, the light wavelength, the fiber core radius, and the length of the bent section. For this purpose, a ray-tracing model is used, which combines both the generalized Fresnel power transmission coefficients for curved graded-index media and the differential equations that govern the ray paths in highly multimode graded-index fibers. This model is applied to the most recent types of graded-index POF, for which the choice of the core radius and profile exponent is discussed from the point of view of bending losses (the greater the profile exponent and the core radius, the greater the bending losses). The influence of profile exponents different from two is included for the first time