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Furthermore, the potential of such a sensor for estimating other variables is illustrated with the design of an extended Luenberger observer.<\/jats:p>","DOI":"10.3390\/s150304766","type":"journal-article","created":{"date-parts":[[2015,2,26]],"date-time":"2015-02-26T10:07:43Z","timestamp":1424945263000},"page":"4766-4780","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":47,"title":["Design and Test of a Low-Cost RGB Sensor for Online Measurement of Microalgae Concentration within a Photo-Bioreactor"],"prefix":"10.3390","volume":"15","author":[{"given":"Micaela","family":"Benavides","sequence":"first","affiliation":[{"name":"BioSys, University of Mons, Boulevard Dolez 31, 7000 Mons, Belgium"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Johan","family":"Mailier","sequence":"additional","affiliation":[{"name":"BioSys, University of Mons, Boulevard Dolez 31, 7000 Mons, Belgium"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Anne-Lise","family":"Hantson","sequence":"additional","affiliation":[{"name":"BioSys, University of Mons, Boulevard Dolez 31, 7000 Mons, Belgium"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Gerardo","family":"Mu\u00f1oz","sequence":"additional","affiliation":[{"name":"Unidad Acad\u00e9mica Juriquilla, Instituto de Ingenier\u00eda, Universidad Nacional Aut\u00f3noma de M\u00e9xico, Blvd. Juriquilla 3001, Quer\u00e9taro 76230, Mexico"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Alejandro","family":"Vargas","sequence":"additional","affiliation":[{"name":"Unidad Acad\u00e9mica Juriquilla, Instituto de Ingenier\u00eda, Universidad Nacional Aut\u00f3noma de M\u00e9xico, Blvd. Juriquilla 3001, Quer\u00e9taro 76230, Mexico"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jan","family":"Van Impe","sequence":"additional","affiliation":[{"name":"Department of Chemical Engineering, Catholic University of Leuven, 3001 Leuven, Belgium"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Alain","family":"Vande Wouwer","sequence":"additional","affiliation":[{"name":"BioSys, University of Mons, Boulevard Dolez 31, 7000 Mons, Belgium"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2015,2,26]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"621","DOI":"10.1111\/j.1365-313X.2008.03492.x","article-title":"Microalgal triacylglycerols as feedstocks for biofuel production: Perspectives and advances","volume":"54","author":"Hu","year":"2008","journal-title":"Plant J."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"294","DOI":"10.1016\/j.biotechadv.2007.02.001","article-title":"Biodiesel from microalgae","volume":"25","author":"Chisti","year":"2007","journal-title":"Biotechnol. 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Control"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"1225","DOI":"10.1128\/aem.33.5.1225-1228.1977","article-title":"Use of nuclepore filters for counting bacteria by fluorescence microscopy","volume":"33","author":"Hobbie","year":"1977","journal-title":"Appl. Environ. Microbiol."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"1387","DOI":"10.1021\/bp020283u","article-title":"On-line determination of biomass in a microalga bioreactor using a novel computerized flow injection analysis system","volume":"18","author":"Meireles","year":"2002","journal-title":"Biotechnol. Prog."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"237","DOI":"10.1007\/BF00008520","article-title":"The estimation of micro-algal protein content and its meaning to the evaluation of algal biomass I. Comparison of methods for extracting protein","volume":"78","author":"Rausch","year":"1981","journal-title":"Hydrobiologia"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"2525","DOI":"10.1016\/S0043-1354(97)00084-5","article-title":"A simple in vitrofluorescence method for biomass measurements in algal growth inhibition tests","volume":"31","author":"Mayer","year":"1997","journal-title":"Water Res."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"113","DOI":"10.1016\/S0022-0981(97)00141-X","article-title":"The determination of algal biomass (as chlorophyll) in suspended matter from the Elbe estuary and the German Bight: A comparison of high-performance liquid chromatography, delayed fluorescence and prompt fluorescence methods","volume":"222","author":"Wiltshire","year":"1998","journal-title":"J. Exp. Mar. Biol. Ecol."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"405","DOI":"10.1016\/j.snb.2013.05.026","article-title":"Development of a photoelectrochemical sensor for monitoring algal biomass (Chlorella vulgaris)","volume":"185","author":"Jeon","year":"2013","journal-title":"Sens. Actuators B Chem."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"1309","DOI":"10.1023\/A:1010521406607","article-title":"Growth monitoring of a photosynthetic micro-organism (Spirulina platensis) by pressure measurement","volume":"23","author":"Cogne","year":"2001","journal-title":"Biotechnol. Lett."},{"key":"ref_13","unstructured":"De la Torre, C., Mu\u00f1iz, R., and P\u00e9rez, M.A. (2009, January 6\u201311). A new, low-cost, on-line RGB colorimeter for wine industry based on optical fibers. Lisbon, Portugal."},{"key":"ref_14","first-page":"128","article-title":"Optoelectronic sensor device for monitoring the maceration of red wine: Design issues and validation","volume":"63","year":"2014","journal-title":"Measurement"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"247","DOI":"10.1016\/j.jfoodeng.2012.02.025","article-title":"Measuring the colour of virgin olive oils in a new colour scale using a low-cost portable electronic device","volume":"111","author":"Carvajal","year":"2012","journal-title":"J. Food Eng."},{"key":"ref_16","doi-asserted-by":"crossref","unstructured":"Wadi Harun, S., and Arof, H. (2013). Current Developments in Optical Fiber Technology, InTech. Chapter 10.","DOI":"10.5772\/46191"},{"key":"ref_17","unstructured":"Union, I.T. (2002). Parameter Values for the HDTV Standards for Production and International Programme Exchange: Recommendation ITU-R BT.709-5: (Question ITU-R 27\/11), ITU."},{"key":"ref_18","unstructured":"Parallax Home. Available online: http:\/\/www.parallax.com\/."},{"key":"ref_19","unstructured":"Arduino. Available online: http:\/\/arduino.cc\/en."},{"key":"ref_20","unstructured":"Shimadzu Corporation (2006). Shimadzu Visible Spectrophotometer UVmini-1240 Instruction Manual, Shimadzu Corporation."},{"key":"ref_21","unstructured":"Skoog, D., Holler, F., and Crouch, S. (2007). Principles of Instrumental Analysis, Thomson Brooks\/Cole."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"1461","DOI":"10.1128\/jb.95.4.1461-1468.1968","article-title":"Effects of salts on the halophilic alga Dunaliella viridis","volume":"95","author":"Johnson","year":"1968","journal-title":"J. Bacteriol."},{"key":"ref_23","unstructured":"Coutinho, D., and Wouwer, A. (2010). Recent Advances in Optimization and its Applications in Engineering, Springer."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"142","DOI":"10.1016\/j.biortech.2010.06.138","article-title":"Modelling neutral lipid production by the microalga Isochrysis aff. galbana under nitrogen limitation","volume":"102","author":"Mairet","year":"2011","journal-title":"Bioresour. Technol."},{"key":"ref_25","unstructured":"Lofberg, J. (2004, January 4). YALMIP: A toolbox for modeling and optimization in MATLAB. Taipei, Taiwan."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"625","DOI":"10.1080\/10556789908805766","article-title":"Using SeDuMi 1.02, a MATLAB toolbox for optimization over symmetric cones","volume":"11","author":"Sturm","year":"1999","journal-title":"Optim. Methods Softw."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/15\/3\/4766\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T20:42:56Z","timestamp":1760215376000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/15\/3\/4766"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2015,2,26]]},"references-count":26,"journal-issue":{"issue":"3","published-online":{"date-parts":[[2015,3]]}},"alternative-id":["s150304766"],"URL":"https:\/\/doi.org\/10.3390\/s150304766","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2015,2,26]]}}}