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Start Over Topic water activity Publication Year Range Last 50 years
5 results

1. Investigation of Distributed Moisture and Temperature Measurements in Transformers Using Fiber Optics Sensors.

Author

Ansari, Muhammad A., Martin, Daniel, and Saha, Tapan Kumar

Subjects
*MOISTURE measurement, *FIBER optics, *ELECTRIC transformers, *OPTICAL fiber detectors, *TEMPERATURE measurements, *DETECTORS
Abstract

The measurement of water inside a transformer is essential to maintain its reliable operation, as the water content can increase as the transformer ages. This measurement is frequently performed by a utility as a part of its periodic maintenance activities. In this paper, the application of optical fiber sensors as an online method to measure water content of paper inside an operating transformer is presented. There are several advantages of using these sensors, including their size, lightweight, flexibility, multiplexing, no-electromagnetic interference, etc. A unique benefit of fiber optic technology is that sensors can be embedded into the winding structure and operate in areas of high electric field strength. For this work, fiber optic water and temperature sensors are investigated by comparing their measurements to a commercial water activity probe immersed in oil. The study found that the determination of water content by fiber optic sensors compared closely with other techniques, which lead to the conclusion that they can be an effective technology for water measurement in an operational transformer. [ABSTRACT FROM AUTHOR]

Published
2019
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2. Metal complexed-enzymatic hydrolyzed chitosan improves moisture retention of fiber papers by migrating immobilized water to bound state

Author

Chao Lin, Xuejiao Wang, Shuqin Xia, Khizar Hayat, Huijuan Wang, Muhammad Tahir, Shahzad Hussain, Heping Cui, and Xiaoming Zhang

Subjects
Paper, Polymers and Plastics, Water activity, Chemical structure, 02 engineering and technology, 010402 general chemistry, 01 natural sciences, Polyvinyl alcohol, law.invention, Humectant, Chitosan, chemistry.chemical_compound, Hydrolysis, Magazine, Cellulase, law, Papain, Materials Chemistry, Organometallic Compounds, Organic Chemistry, Water, 021001 nanoscience & nanotechnology, nervous system diseases, 0104 chemical sciences, Molecular Weight, Polygalacturonase, chemistry, Wettability, Molar mass distribution, 0210 nano-technology, Hydrophobic and Hydrophilic Interactions, Nuclear chemistry
Abstract

To obtain chitosan (CTS) with narrower molecular weight distribution, CTS with weight-average molecular weight (MW) of 197.30 kDa was first metal complexed and then degraded into five CTSs with MW of 107.90, 56.48, 10.40, 5.67 (CTS-4) and 3.66 kDa. Decrease of MW did not cause a significant change in chemical structure of the residue CTS, but the crystal structure was transformed significantly. The moisture retention increased firstly and then decreased as the MW of CTS decreased. CTS-4 was superior to CTSs with other MW and propylene glycol in terms of the moisture retention. The lower water activity and increase of net isosteric heat were observed in CTS-4, which was due to the migration of immobilized water to a bound-state caused by mounting newly formed chain-end hydrophilic groups per unit weight. CTS-4 could effectively improve moisture retention, showing a potential to substitute commonly used humectant such as propylene glycol.

Published
2019

3. Moisture distribution in sludges based on different testing methods

Author

Wenyi Deng, Kefa Cen, Fei Wang, Xiaodong Li, Yong Chi, and Jianhua Yan

Subjects
Paper, Environmental Engineering, Water activity, Industrial Waste, Sewage, Chemistry Techniques, Analytical, Environmental Chemistry, Bound water, Cities, Desiccation, Coloring Agents, Water content, General Environmental Science, Calorimetry, Differential Scanning, Moisture, business.industry, Chemistry, Temperature, Environmental engineering, Water, Humidity, Paper mill, General Medicine, Pulp and paper industry, Thermogravimetry, Printing, business, Surface water
Abstract

Moisture distributions in municipal sewage sludge, printing and dyeing sludge and paper mill sludge were experimentally studied based on four different methods, i.e., drying test, thermogravimetric-differential thermal analysis (TG-DTA) test, thermogravimetric-differential scanning calorimetry (TG-DSC) test and water activity test. The results indicated that the moistures in the mechanically dewatered sludges were interstitial water, surface water and bound water. The interstitial water accounted for more than 50% wet basis (wb) of the total moisture content. The bond strength of sludge moisture increased with decreasing moisture content, especially when the moisture content was lower than 50% wb. Furthermore, the comparison among the four different testing methods was presented. The drying test was advantaged by its ability to quantify free water, interstitial water, surface water and bound water; while TG-DSC test, TG-DTA test and water activity test were capable of determining the bond strength of moisture in sludge. It was found that the results from TG-DSC and TG-DTA test are more persuasive than water activity test.

Published
2011
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4. Effect of different new packaging materials on biscuit quality during accelerated storage

Author

Pietro Rocculi, Marco Dalla Rosa, Valentina Siracusa, Federica Balestra, Santina Romani, Silvia Tappi, Maria Teresa Rodriguez Estrada, S. Romani, S. Tappi, F. Balestra, M. T. Rodriguez-Estrada, V. Siracusa, P. Rocculi, and M. Dalla Rosa

Subjects
Paper, Vinyl Compounds, Materials science, Water activity, Polymers, Polyesters, Biscuits, Innovative Packaging, Quality, Polypropylenes, Shelf life, Hexanal, chemistry.chemical_compound, Lipid oxidation, Food Preservation, Food Quality, Lactic Acid, Food science, Innovative packaging, Nutrition and Dietetics, Moisture, Shelf-life, Food Packaging, Water, Ethylene-vinyl acetate, Humidity, Ethylenes, Food packaging, chemistry, Metals, Polyvinyls, Lipid Peroxidation, Food quality, Agronomy and Crop Science, Biscuit, Food Science, Biotechnology
Abstract

BACKGROUND The effect of innovative multilayer packaging materials versus a standard one on biscuit quality was studied during accelerated storage at 25, 35, 45 °C and 50% relative humidity for 92 days. Three different packaging materials were used: metalized orientated polypropylene (OPP)/paper (control); metalized poly-lactic acid (PLA)/paper; metalized OPP with ethylene vinyl acetate pro-oxidant additive (EVA-POA)/paper. EVA-POA additive is used to make the plastic layer biodegradable. Various quality sample parameters (moisture, water activity (aw), texture, peroxide value (PV), hexanal) were analysed during storage. Rate constants (k) and activation energies (Ea) of hydration reactions and hexanal formation were calculated. RESULTS No remarkable differences in the evolution of primary and secondary lipid oxidation were observed among differently packed biscuits during storage. All samples maintained PV levels between 4 and 14 meq O2 kg−1 oil. The product in flexible packaging with PLA reached the highest moisture and aw levels, but they did not significantly and adversely affect the other quality characteristics. CONCLUSION The obtained results demonstrate that the new tested packaging materials were suitable for commercial biscuit storage, having similar performance and preservation effects on the overall product quality to those of the standard one. Furthermore, these results could make a contribution to the food industry, encouraging the use of packaging materials with a negligible environmental impact as an alternative to petroleum-based ones. © 2014 Society of Chemical Industry

Published
2015

5. Effect of relative humidity on the migration of benzophenone from paperboard into the food simulant Tenax® and modelling hereof

Author

Line Lundbæk Barnkob and Jens Højslev Petersen

Subjects
Paper, Water activity, Polymers, Health, Toxicology and Mutagenesis, Diffusion, Tenax, Food Contamination, Toxicology, chemistry.chemical_compound, Benzophenones, Benzophenone, Organic chemistry, Humans, Relative humidity, Composite material, Paperboard, Public Health, Environmental and Occupational Health, Food Packaging, Humidity, General Chemistry, General Medicine, Models, Theoretical, Food packaging, Partition coefficient, chemistry, visual_art, visual_art.visual_art_medium, Food Science
Abstract

The aim of this study was to investigate the effect of relative humidity on the migration of benzophenone from paperboard into the food simulant Tenax®. Kinetic migration investigations were carried out with three relative humidities in the interval between 39% and73%. All investigations were carried out at a constant temperature of 34°C. It was found that the migration of benzophenone after more than 30 days was 4.8 times higher at a relative humidity of 64%-71%, and 7.3 times higher at a relative humidity of73%, compared with that at a relative humidity of 39%-49%. Diffusion and partition coefficients were derived from the results by using a software for modelling migration in multilayer materials. Both the diffusion coefficient and the partition coefficient, between paperboard and Tenax®, decrease with increasing relative humidity. The experimental results were correctly modelled only when the paperboard was regarded as a one-layer system as compared with a two-layer system: where the main part of the paperboard (B1) has a high diffusion rate and a thin part of the paperboard (B2) in contact with the foodstuff has a lower diffusion rate.

Published
2012