Different types of fiber-optic sensors based on glass or polymeric fibers are used to evaluate material behavior or to monitor the integrity and long-term stability of load-bearing structure components. Fiber-optic se...Different types of fiber-optic sensors based on glass or polymeric fibers are used to evaluate material behavior or to monitor the integrity and long-term stability of load-bearing structure components. Fiber-optic sensors have been established as a new and innovative measurement technology in very different fields, such as material science, civil engineering, light-weight structures, geotechnical areas as well as chemical and high-voltage substations. Very often, mechanical quantities such as deformation, strain or vibration are requested. However, measurement of chemical quantities in materials and structure components, such as pH value in steel reinforced concrete members also provides information about the integrity of concrete structures. A special fiber-optic chemical sensor for monitoring the alkaline state （pH value） of the cementitious matrix in steel-reinforced concrete structures with the purpose of early detection of corrosion-initiating factors is described. The paper presents the use of several fiber-optic sensor technologies in engineering. One example concerns the use of highly resolving concrete-embeddable fiber Fabry-Perot acoustic emission （AE） sensors for the assessment of the bearing behaviour of large concrete piles in existing foundations or during and after its installation. Another example concerns fiber Bragg grating （FBG） sensors attached to anchor steels （micro piles） to measure the strain distribution in loaded soil anchors. Polymer optical fibers （POF） can be -- because of their high elasticity and high ultimate strain - well integrated into textiles to monitor their deformation behaviour. Such ＂intelligent＂ textiles are capable of monitoring displacement of soil or slopes, critical mechanical deformation in geotechnical structures （dikes, dams, and embankments） as well as in masonry structures during and after earthquakes.展开更多
Milk spoilage is an indefinite term and difficult to measure with accuracy. This uncertainty can cause suffering for both milk manufacturers and consumers. Consumers who have been misled by ambiguous expiration dates ...Milk spoilage is an indefinite term and difficult to measure with accuracy. This uncertainty can cause suffering for both milk manufacturers and consumers. Consumers who have been misled by ambiguous expiration dates on milk cartons waste resources by disposing of unspoiled milk or experience discomfort from drinking spoiled milk. Consumers are often unwilling to purchase products close to their inaccurate expiration dates. This consumer behavior has a negative financial impact on milk producers. Inaccurate milk spoilage detection methods also force milk producers to use overly conservative expiration dates in an effort to avoid the legal and economic consequences of consumers experiencing illness from drinking spoiled milk. Over the last decade, new methods have been researched with the purpose of developing more accurate and efficient means of detecting milk spoilage. These methods include indicators based on pH bacteria counts and gas-sensor arrays. This article explores various methods of spoilage detection designed to prevent such consequences. The respective level of effectiveness of each method is discussed, as well as several further approaches to contain freshness regardless of detection.展开更多
文摘Different types of fiber-optic sensors based on glass or polymeric fibers are used to evaluate material behavior or to monitor the integrity and long-term stability of load-bearing structure components. Fiber-optic sensors have been established as a new and innovative measurement technology in very different fields, such as material science, civil engineering, light-weight structures, geotechnical areas as well as chemical and high-voltage substations. Very often, mechanical quantities such as deformation, strain or vibration are requested. However, measurement of chemical quantities in materials and structure components, such as pH value in steel reinforced concrete members also provides information about the integrity of concrete structures. A special fiber-optic chemical sensor for monitoring the alkaline state （pH value） of the cementitious matrix in steel-reinforced concrete structures with the purpose of early detection of corrosion-initiating factors is described. The paper presents the use of several fiber-optic sensor technologies in engineering. One example concerns the use of highly resolving concrete-embeddable fiber Fabry-Perot acoustic emission （AE） sensors for the assessment of the bearing behaviour of large concrete piles in existing foundations or during and after its installation. Another example concerns fiber Bragg grating （FBG） sensors attached to anchor steels （micro piles） to measure the strain distribution in loaded soil anchors. Polymer optical fibers （POF） can be -- because of their high elasticity and high ultimate strain - well integrated into textiles to monitor their deformation behaviour. Such ＂intelligent＂ textiles are capable of monitoring displacement of soil or slopes, critical mechanical deformation in geotechnical structures （dikes, dams, and embankments） as well as in masonry structures during and after earthquakes.
文摘通过浸涂法在钨金属丝上涂敷氧化钨氢离子敏感膜，制备了氧化钨H＋选择性电极，采用尿素改性聚乙烯醇作为参比电极的固态薄膜材料并进行KCl掺杂，经Nafion膜进行修饰后制备了固态参比电极.利用自制的氧化钨pH电极与固态参比电极制成pH电化学传感器，该传感器具有良好的响应电位E-pH线性函数关系，响应范围为pH2~pH11.响应灵敏度与氧化钨的热处理温度有关，200℃热处理后的响应灵敏度为52.81 mV/pH，响应时间与氧化钨敏感膜、测试溶液pH值以及溶液温度有关.在pH2→pH11→pH2循环测试过程中，传感器的滞后效应较小.该传感器有良好的选择性，响应行为不受Na＋、F-等常见离子的影响，但是受到氧化还原性的NO-3、I-等离子的干扰.传感器内阻很低为22.8 kΩ，远小于玻璃pH计的内阻（1×109Ω）.该传感器在各种饮料中具有较高测量精度，与玻璃pH计的测量值进行对比，两者的差值在（-0.06 pH，＋0.15pH）范围内.在10-5M→10-1M柠檬酸溶液中，传感器的响应电位与溶液浓度存在良好的线性关系，响应时间小于1 min.
文摘Milk spoilage is an indefinite term and difficult to measure with accuracy. This uncertainty can cause suffering for both milk manufacturers and consumers. Consumers who have been misled by ambiguous expiration dates on milk cartons waste resources by disposing of unspoiled milk or experience discomfort from drinking spoiled milk. Consumers are often unwilling to purchase products close to their inaccurate expiration dates. This consumer behavior has a negative financial impact on milk producers. Inaccurate milk spoilage detection methods also force milk producers to use overly conservative expiration dates in an effort to avoid the legal and economic consequences of consumers experiencing illness from drinking spoiled milk. Over the last decade, new methods have been researched with the purpose of developing more accurate and efficient means of detecting milk spoilage. These methods include indicators based on pH bacteria counts and gas-sensor arrays. This article explores various methods of spoilage detection designed to prevent such consequences. The respective level of effectiveness of each method is discussed, as well as several further approaches to contain freshness regardless of detection.
