{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,10]],"date-time":"2026-06-10T14:19:22Z","timestamp":1781101162083,"version":"3.54.1"},"reference-count":76,"publisher":"MDPI AG","issue":"7","license":[{"start":{"date-parts":[[2018,6,22]],"date-time":"2018-06-22T00:00:00Z","timestamp":1529625600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Lubricant and hydraulic fluid ageing impacts the performance of the machines, gears, transmissions or automatisms where they are being used. This manuscript describes the work accomplished for bringing an innovative measurement concept for analysing the physical- chemical properties of these fluids, to a real industrial product ready to be integrated into different industrial equipment. The steps taken to deal with uncertainties and evolving requirements while progressing in the sensor development are described, covering the stages of theoretical formulation of the problem, optical and fluidic simulations, sensor prototype development and tests. The sensor working principle is based on a combination of transmittance and diffuse reflectance photonic inspection of the fluid sample that is collected in a microcavity through a standard hydraulic fitting. Photonics, electronics, micro-mechanics, fluidics, data processing and analysis has been merged with a deep knowledge in the lubricant degradation process to develop a sensor solution that is able to measure the Oil Degradation Index, Oil Oxidation, Acid Number, Ruler and Membrane Patch Colorimetry data from an inservice lubricating oil sample. The photonic micro sensor presented here offers a powerful tool that operates directly immersed in the fluid, at an economic cost and compacted size for inline oil degradation monitoring.<\/jats:p>","DOI":"10.3390\/s18072015","type":"journal-article","created":{"date-parts":[[2018,6,22]],"date-time":"2018-06-22T10:56:28Z","timestamp":1529664988000},"page":"2015","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":20,"title":["Low Cost Photonic Sensor for in-Line Oil Quality Monitoring: Methodological Development Process towards Uncertainty Mitigation"],"prefix":"10.3390","volume":"18","author":[{"given":"Patricia","family":"Lopez","sequence":"first","affiliation":[{"name":"IK4-Tekniker, 20600 Eibar, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jon","family":"Mabe","sequence":"additional","affiliation":[{"name":"IK4-Tekniker, 20600 Eibar, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Guillermo","family":"Mir\u00f3","sequence":"additional","affiliation":[{"name":"atten2 Advanced Monitoring Technologies, 20600 Eibar, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Leire","family":"Etxeberria","sequence":"additional","affiliation":[{"name":"Mondragon Unibertsitatea, 20600 Eibar, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2018,6,22]]},"reference":[{"key":"ref_1","unstructured":"Mang, T., and Dressel, W. (2017). Lubricants and Lubrication, Jonh Wiley & Sons. [3rd ed.]."},{"key":"ref_2","unstructured":"G\u00f3mez Estrada, Y.A. (2013). Contribuci\u00f3n al Desarrollo y Mejora Para la Cuantificaci\u00f3n de la Degradaci\u00f3n en Aceites Lubricantes Usados de MCIA a Trav\u00e9s de la T\u00e9cnica de Espectrometr\u00eda Infrarroja por Transformada de Fourier (FT-IR). [Ph.D. Thesis, Universitat Polit\u00e8cnica de Val\u00e8ncia]."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"67","DOI":"10.4236\/aces.2016.62008","article-title":"Performance Deterioration Analysis of the Used Gear Oil","volume":"6","author":"Zeng","year":"2016","journal-title":"Adv. Chem. Eng. Sci."},{"key":"ref_4","unstructured":"H\u00f6hn, B.R., and Michaellis, K. (2018, May 03). Influence of Lubricant Ageing on Gear Performance. Available online: http:\/\/www.oetg.at\/fileadmin\/Dokumente\/oetg\/Proceedings\/WTC_2001_files\/html\/M-28-02-339-HOEHN.pdf."},{"key":"ref_5","unstructured":"Wright, J. (2018, May 03). 3 Reasons Why Lube Oils Fail, Machinery Lubrication, August 2011. Available online: http:\/\/www.machinerylubrication.com\/Read\/28526\/why-lube-oils-fail."},{"key":"ref_6","unstructured":"Neale, M.J. (2000). Lubrication and Reliability Book, Newness. [1st ed.]."},{"key":"ref_7","unstructured":"Richardson, D. (2013). Plant Equipment & Maintenance Engineering Handbook, McGraw Hill Professional."},{"key":"ref_8","unstructured":"Kopschinsky, J. (2018, May 03). The True Cost of Poor Lubrication. Available online: http:\/\/www.uesystems.com\/wp-content\/uploads\/2014\/10\/The-True-Cost-of-Poor-Lubrication.pdf."},{"key":"ref_9","unstructured":"(2018, May 03). Atten2 Advanced Monitoring Technologies. Available online: http:\/\/atten2.com\/."},{"key":"ref_10","unstructured":"Gebarin, S. (2018, May 03). On-Line and In-Line Wear Debris Detectors: What\u2019s Out There? Machinery Lubrication, September 2003. Available online: http:\/\/www.machinerylubrication.com\/read\/521\/in-line-wear-debris-detectors."},{"key":"ref_11","doi-asserted-by":"crossref","unstructured":"Myshkin, N.K., and Markova, L.V. (2018). On-Line Condition Monitoring in Industrial Lubrication and Tribology, Springer. [1st ed.].","DOI":"10.1007\/978-3-319-61134-1"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"619","DOI":"10.1109\/JIOT.2017.2664072","article-title":"Structural health monitoring framework based on Internet of Things: A survey","volume":"4","author":"Tokognon","year":"2017","journal-title":"IEEE Internet Things J."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"02008","DOI":"10.1051\/matecconf\/201712102008","article-title":"Application of IoT concept on predictive maintenance of industrial equipment","volume":"121","author":"Parpala","year":"2017","journal-title":"MATEC Web Conf."},{"key":"ref_14","unstructured":"(2018, May 11). Los Sensors: Herramientas Clave Para el Desarrollo del \u2018Big-Data\u2019 (Sensor: Key Tools for the Development of Big Data). Available online: http:\/\/www.spri.eus\/es\/ris3-euskadi-comunicacion\/los-sensores-herramientas-clave-desarrollo-del-big-data\/."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"18","DOI":"10.1016\/j.mfglet.2014.12.001","article-title":"A Cyber-Physical Systems architecture for Industry 4.0-based manufacturing systems","volume":"3","author":"Lee","year":"2015","journal-title":"Manuf. Lett."},{"key":"ref_16","unstructured":"(2018, May 03). Siemens and General Electric Gear up for the Internet of Things, The Economist, December 2016. Available online: https:\/\/www.economist.com\/news\/business\/21711079-american-industrial-giant-sprinting-towards-its-goal-german-firm-taking-more."},{"key":"ref_17","unstructured":"(2018, May 03). Intelligent Sensor Systems for Industry 4.0, Press Release, Bosch Group. Available online: http:\/\/www.bosch-presse.de\/pressportal\/de\/en\/intelligent-sensor-systems-for-industry-4-0-44893.html."},{"key":"ref_18","unstructured":"(2018, May 03). Machine Monitoring with Smart Sensors, Press Release, Bosch Group. Available online: http:\/\/www.bosch-presse.de\/pressportal\/de\/en\/machine-monitoring-with-smart-sensors-44917.html."},{"key":"ref_19","doi-asserted-by":"crossref","unstructured":"Gresham, R.M., and Totten, G.E. (2008). Lubrication and Maintenance of Industrial Machinery: Best Practices and Reliability, CRC Press.","DOI":"10.1201\/9781420089363"},{"key":"ref_20","unstructured":"(2018, May 08). Industry 4.0 Challenges and Solutions for the Digital Transformation and Use of Exponential Technologies, Deloitte, 2015. Available online: https:\/\/www2.deloitte.com\/content\/dam\/Deloitte\/ch\/Documents\/manufacturing\/ch-en-manufacturing-industry-4-0-24102014.pdf."},{"key":"ref_21","unstructured":"Mabe, J. (2017). Photonic Low-Cost Sensors for in-Line Fluid Monitoring, Euskal Herriko Unibertsitatea. Available online: http:\/\/hdl.handle.net\/10810\/25046."},{"key":"ref_22","first-page":"681","article-title":"Key Concepts in Innovation","volume":"4","author":"Thota","year":"2012","journal-title":"J. Prod. Innov. Manag."},{"key":"ref_23","unstructured":"(2018, May 07). The Fast Track to Success with Agile Product Development, Bosch Group. Available online: http:\/\/www.bosch-presse.de\/pressportal\/de\/en\/the-fast-track-to-success-with-agile-product-development-42983.html."},{"key":"ref_24","first-page":"32","article-title":"Past, Present and Future of Oil Analysis: An Expert Panel Discussion on the Future of Oil Analysis","volume":"64","author":"Johnson","year":"2007","journal-title":"Tribol. Lubr. Trans."},{"key":"ref_25","unstructured":"Zhao, Y. (2014). Oil Analysis Handbook, Spectro Scientific. [1st ed.]. Available online: https:\/\/www.spectrosci.com\/default\/assets\/File\/SpectroSci_OilAnalysisHandbook_FINAL_2014-08.pdf."},{"key":"ref_26","unstructured":"Toms, L.A., and Toms, A.M. (2008). Machinery Oil Analysis: Methods, Automation & Benefits, STLE. [3rd ed.]."},{"key":"ref_27","unstructured":"(2018, May 04). ASTM D974-14e2, Standard Test Method for Acid Number and Base Number by Color-Indicator Titration, West Conshohocken, PA. Available online: http:\/\/www.astm.org\/Standards\/D974."},{"key":"ref_28","unstructured":"(2018, May 04). ASTM D664-17a, Standard Test Method for Acid Number of Petroleum Products by Potentiometric Titration, ASTM International, West Conshohocken, PA. Available online: http:\/\/www.astm.org\/Standards\/D664."},{"key":"ref_29","first-page":"20","article-title":"Best practices: Strategic oil analysis: Setting the test slate","volume":"65","author":"Johnson","year":"2009","journal-title":"Tribol. Lubr. Technol."},{"key":"ref_30","unstructured":"(2018, May 04). ASTM D6971-09(2014), Standard Test Method for Measurement of Hindered Phenolic and Aromatic Amine Antioxidant Content in Non-Zinc Turbine Oils by Linear Sweep Voltammetry, ASTM International, West Conshohocken, PA. Available online: http:\/\/www.astm.org\/Standards\/D6971."},{"key":"ref_31","unstructured":"(2018, May 04). ASTM D6810-13, Standard Test Method for Measurement of Hindered Phenolic Antioxidant Content in Non-Zinc Turbine Oils by Linear Sweep Voltammetry, ASTM International, West Conshohocken, PA. Available online: http:\/\/www.astm.org\/Standards\/D6810."},{"key":"ref_32","unstructured":"(2018, May 04). ASTM E2412-10, Standard Practice for Condition Monitoring of Used Lubricants by Trend Analysis Using Fourier Transform Infrared (FT-IR) Spectrometry, ASTM International, West Conshohocken, PA. Available online: http:\/\/www.astm.org\/Standards\/E2412."},{"key":"ref_33","unstructured":"(2018, May 04). ASTM D445-17a, Standard Test Method for Kinematic Viscosity of Transparent and Opaque Liquids (and Calculation of Dynamic Viscosity), ASTM International, West Conshohocken, PA. Available online: http:\/\/www.astm.org\/Standards\/D445."},{"key":"ref_34","unstructured":"(2018, May 04). ASTM D1500-12(2017), Standard Test Method for ASTM Color of Petroleum Products (ASTM Color Scale), ASTM International, West Conshohocken, PA. Available online: http:\/\/www.astm.org\/Standards\/D1500."},{"key":"ref_35","unstructured":"(2018, May 04). ASTM D7843-16, Standard Test Method for Measurement of Lubricant Generated Insoluble Color Bodies in In-Service Turbine Oils Using Membrane Patch Colorimetry, ASTM International, West Conshohocken, PA. Available online: http:\/\/www.astm.org\/Standards\/D7843."},{"key":"ref_36","first-page":"74","article-title":"Detecting and solving lube oil varnish problems","volume":"151","author":"Livingstone","year":"2007","journal-title":"Power"},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"10675","DOI":"10.3390\/s111110675","article-title":"Low-Cost Oil Quality Sensor Based on Changes in Complex Permittivity","volume":"11","author":"Torres","year":"2011","journal-title":"Sensors"},{"key":"ref_38","doi-asserted-by":"crossref","unstructured":"Rauscher, M., Tremmel, A.J., Schardt, M., and Koch, A.W. (2017). Non-Dispersive Infrared Sensor for Online Condition Monitoring of Gearbox Oil. Sensors, 17.","DOI":"10.3390\/s17020399"},{"key":"ref_39","doi-asserted-by":"crossref","unstructured":"Han, Z., Wang, Y., and Qing, X. (2017). Characteristics Study of In-Situ Capacitive Sensor for Monitoring Lubrication Oil Debris. Sensors, 17.","DOI":"10.3390\/s17122851"},{"key":"ref_40","doi-asserted-by":"crossref","unstructured":"Chen, Y., Mei, G., Yang, H., Yu, F., and Gao, J. (2016). Performance Characteristics and Temperature Compensation Method of Fluid Property Sensor Based on Tuning-Fork Technology. J. Sens., 1386564.","DOI":"10.1155\/2016\/1386564"},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"020099","DOI":"10.1063\/1.5029675","article-title":"Capacitive sensor for engine oil deterioration measurement","volume":"1943","author":"Shinde","year":"2018","journal-title":"AIP Conf. Proc."},{"key":"ref_42","doi-asserted-by":"crossref","unstructured":"Riziotis, C., El Sachat, A., Markos, C., Velanas, P., Meristoudi, A., and Papadopoulos, A. (2015;, January 7\u201310). Assessment of fiber optic sensors for aging monitoring of industrial liquid coolants. Proceedings of the SPIE\u2014The International Society for Optical Engineering, Jena, Germany. Article No. 93591Y.","DOI":"10.1117\/12.2079988"},{"key":"ref_43","unstructured":"Weling, A.S., Girgenti, R.S., Fratkin, M.B., and Henning, P.F. (2016). In-Situ Fluid Analysis Sensor Bolt. (No. US9228956B2), U.S. Patent."},{"key":"ref_44","unstructured":"Miranda, R., Pacheco, G., and Valadez, R. (2016). Device for In-Line Monitoring of Fluid Colours. (No. WO2016080824A4), Patent Application."},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"349","DOI":"10.1108\/00368791011076245","article-title":"Utilization of color change in the condition monitoring of synthetic hydraulic oils","volume":"62","author":"Ossia","year":"2010","journal-title":"Ind. Lubr. Tribol."},{"key":"ref_46","first-page":"44","article-title":"How Wedge and Decenter Affect Aspheric Optics","volume":"47","author":"Filhaber","year":"2013","journal-title":"Photonics Spectra"},{"key":"ref_47","unstructured":"Hill, D., and McEuen, K. (2018, May 07). 4 Big Mistakes in Developing Photonics-Enabled Medical Devices. White Paper, Zygo Corporation. Available online: https:\/\/www.meddeviceonline.com\/doc\/big-mistakes-in-developing-photonics-enabled-medical-devices-0001."},{"key":"ref_48","doi-asserted-by":"crossref","unstructured":"Aranzabe, E., Marcaide, A., Arnaiz, A., and Hernaiz, M. (2008). New method proposed for the assessment of lubricant biodegradability during its use. J. Near Infrared Spectrosc., 16.","DOI":"10.1255\/jnirs.790"},{"key":"ref_49","unstructured":"Terradillos, J., Arnaiz, A., Gorritxategi, E., Aranzabe, A., and Aranzabe, E. (2008, January 4\u20136). Novel Method for Lube Quality Status Assessment Based on Visible Spectrometric Analysis. Proceedings of the Lubrication Management and Technology (Lubmat) 2008, San Sebastian, Spain."},{"key":"ref_50","doi-asserted-by":"crossref","unstructured":"Halme, J., Gorritxategi, E., and Bellew, J. (2010). Lubricating Oil Sensors. E-Maintenance, Springer. [1st ed.].","DOI":"10.1007\/978-1-84996-205-6_7"},{"key":"ref_51","doi-asserted-by":"crossref","first-page":"113","DOI":"10.1109\/TMAG.2012.2217117","article-title":"Magnetoelastic Viscosity Sensor for On-Line Status Assessment of Lubricant Oils","volume":"49","author":"Gorritxategi","year":"2013","journal-title":"IEEE Trans. Magn."},{"key":"ref_52","unstructured":"Gorritxategi, E., Arnaiz, A., Aranzabe, A., and Terradillos, J. (2018). Method and Device for Determining the State of Degradation of a Lubricant Oil. (No. EP2615444B1), U.S. Patent."},{"key":"ref_53","unstructured":"Gorritxategi, E. (2013). Dispositivo Sensor \u00d3ptico Para Determinaci\u00f3n del Estado de Degradaci\u00f3n de un Aceite Lubricante en un Circuito de Lubricaci\u00f3n de una M\u00e1quina. (Patent Specification No. ES2455465B1)."},{"key":"ref_54","doi-asserted-by":"crossref","first-page":"53","DOI":"10.4028\/www.scientific.net\/KEM.644.53","article-title":"Innovative On-Line Oil Sensor Technologies for the Condition Monitoring of Wind Turbines","volume":"644","author":"Gorritxategi","year":"2014","journal-title":"Key Eng. Mater."},{"key":"ref_55","unstructured":"Gorritxategi, E., and Mabe, J. (2016). System and Method for Monitoring a Fluid. (Application EP2980557A1), European Patent."},{"key":"ref_56","first-page":"77262F","article-title":"Visible\/NIR on-line sensor for marine engine oil condition monitoring applying chemometric methods","volume":"7726","author":"Villar","year":"2010","journal-title":"Int. Soc. Opt. Eng."},{"key":"ref_57","doi-asserted-by":"crossref","first-page":"68","DOI":"10.1016\/j.chemolab.2013.10.008","article-title":"Optimization of the multivariate calibration of a Vis-NIR sensor for the on-line monitoring of marine diesel engine lubricating oil by variable selection methods","volume":"130","author":"Villar","year":"2014","journal-title":"Chemom. Intell. Lab. Syst."},{"key":"ref_58","doi-asserted-by":"crossref","first-page":"2756","DOI":"10.1016\/j.foodchem.2012.07.074","article-title":"Low-cost visible-near infrared sensor for on-line monitoring of fat and fatty acids content during the manufacturing process of the milk","volume":"135","author":"Villar","year":"2012","journal-title":"Food Chem."},{"key":"ref_59","doi-asserted-by":"crossref","unstructured":"Mabe, J., Zubia, J., and Gorritxategi, E. (2017). Photonic Low Cost Micro-Sensor for in-Line Wear Particle Detection in Flowing Lube Oils. Sensors, 17.","DOI":"10.3390\/s17030586"},{"key":"ref_60","unstructured":"Gorritxategi, E., Mabe, J., Delgado, A., Villar, A., and Urreta, H. (2017). Fluid Monitoring System Based on Near-Infrared Spectroscopy. (Application EP3176565A1), European Patent."},{"key":"ref_61","doi-asserted-by":"crossref","unstructured":"Flammer, J., Mozaffarieh, M., and Bebie, H. (2013). The Interaction between Light and Matter. Basic Sciences in Ophthalmology, Springer. [1st ed.].","DOI":"10.1007\/978-3-642-32261-7"},{"key":"ref_62","doi-asserted-by":"crossref","unstructured":"Workman, J.J.J. (2016). Concise Handbook of Analytical Spectroscopy, the: Theory, Applications, and Reference Materials: Volume 2: Visible Spectroscopy, World Scientific Publishing Company.","DOI":"10.1142\/8800-vol2"},{"key":"ref_63","unstructured":"Lindon, J.C., Tranter, G.E., and Koppenaal, D.W. (2016). Encyclopedia of Spectroscopy and Spectrometry, Academic Press. [3rd ed.]."},{"key":"ref_64","unstructured":"McGrath, R.G., and Macmillan, I.C. (2009). Discovery-Driven Growth: A Breakthrough Process to Reduce Risk and Seize Opportunity, Harvard Review Press. [1st ed.]."},{"key":"ref_65","doi-asserted-by":"crossref","unstructured":"Loch, C.H., DeMever, A., and Pich, M. (2006). Managing the Unknown: A New Approach to Managing High Uncertainty and Risk in Projects, John Wiley & Sons, Inc.","DOI":"10.1002\/9780470172377"},{"key":"ref_66","doi-asserted-by":"crossref","first-page":"32","DOI":"10.1525\/cmr.2010.53.1.32","article-title":"Lost Roots: How Project Management Came to Emphasize Control Over Flexibility and Novelty","volume":"53","author":"Lenfle","year":"2010","journal-title":"Calif. Manag. Rev."},{"key":"ref_67","unstructured":"Mabe, J. (2018, May 11). From the Innovative Idea to the High Added-Value Product. Newtek (10), IK4-TEKNIKER. Available online: http:\/\/www.newtek-tech.es\/newtek\/boletin\/10\/eng\/especialista1.php."},{"key":"ref_68","unstructured":"(2018, May 08). Role of Design for Six Sigma in Total Product Development, Six Sigma Academy International LCC. Available online: https:\/\/lgosdm.mit.edu\/VCSS\/web_seminars\/docs\/eskandari_052606.pdf."},{"key":"ref_69","unstructured":"Ries, E. (2011). The Lean Startup: How Today\u2019s Entrepreneurs Use Continuous Innovation to Create Radically Successful Businesses, Crown Business, Crown Publishing Group."},{"key":"ref_70","unstructured":"Chesbrough, H.W. (2006). Open Innovation: The New Imperative for Creating and Profiting from Technology, Harvard Business School Press. [1st ed.]."},{"key":"ref_71","first-page":"20","article-title":"Invited Article: What\u2019s Next? After Stage-Gate","volume":"57","author":"Cooper","year":"2014","journal-title":"Res.-Technol. Manag."},{"key":"ref_72","unstructured":"Frick, B., and Schenkel, B. (2008). Spectral Photometer and Associated Measuring Head. (US7365843B2), U.S. Patent."},{"key":"ref_73","doi-asserted-by":"crossref","unstructured":"Hrbac, R., Kolar, V., Novak, T., and Bart\u0142omiejczyk, M. (2014, January 12\u201314). Prototype of a low-cost luxmeter with wide measuring range designed for railway stations dynamic lighting systems. Proceedings of the 2014 15th International Scientific Conference on Electric Power Engineering (EPE), Brno, Czech Republic.","DOI":"10.1109\/EPE.2014.6839496"},{"key":"ref_74","doi-asserted-by":"crossref","unstructured":"Cussler, E.L. (2009). Diffusion Mass Transfer in Fluid Systems, Cambridge University Press. [3rd ed.].","DOI":"10.1017\/CBO9780511805134"},{"key":"ref_75","unstructured":"Tyrrel, H.J.V., and Harris, K.R. (1984). Diffusion in Liquids: A Theoretical and Experimental Study, Butterworth-Heinemann. [1st ed.]."},{"key":"ref_76","unstructured":"(2018, May 03). HAMAMATSU Color\/proximity Sensor. Available online: https:\/\/www.hamamatsu.com\/resources\/pdf\/ssd\/p12347-01ct_kpic1084e.pdf."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/18\/7\/2015\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T15:09:51Z","timestamp":1760195391000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/18\/7\/2015"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2018,6,22]]},"references-count":76,"journal-issue":{"issue":"7","published-online":{"date-parts":[[2018,7]]}},"alternative-id":["s18072015"],"URL":"https:\/\/doi.org\/10.3390\/s18072015","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2018,6,22]]}}}