Studies on Sensor Networks with Fiber Optics for Agricultural Environment Monitoring

創価大

Optical fiber sensors for in-situ detection of solid-liquid phase change for n-octadecane

In the past few decades solid-liquid phase change materials (PCMs) have gained an increasingly important role in thermal energy storage applications due to their ability to absorb or release large amounts of energy during melting or solidification. The precise phase change temperature varies with different conditions, such as external pressure, small variations in the PCM composition in the case of multi-component mixtures and/or material purity. In order to achieve better energy efficiency for the energy storage process, it is necessary to be able to accurately detect the solid-liquid phase changes in the bulk of a PCM. Optical fiber sensors allow for direct detection of the phase changes in PCMs while also offering the advantages of a passive nature and small size. The focus of the research presented in this thesis is on the development of a novel approach to detecting the solid-liquid phase changes in selected PCMs using optical fiber sensors. To achieve this goal, initially the correlation between the temperature, changes in the refractive index (RI) and internal pressure acting upon the optical fiber during the phase transitions was studied for the selected PCM, n-octadecane. Based on the results of these studies, several optical fiber sensing structures have been proposed and demonstrated for the detection of phase changes as follows: An optical fiber Fresnel reflection sensor for detection of phase changes. An fiber Fresnel reflection sensor for detection of solid-liquid phase change in n-octadecane is proposed and experimentally demonstrated. The sensor probe consists of a single-mode fiber with a cleaved end immersed in the n-octadecane sample under test. The detection relies on measuring the slope of the output power ratio change which is caused by the RI change during the phase transition. The results of this work suggest that such a simple optical fiber sensor can be used for detection of liquid-solid phase changes in other materials with similar thermo-optic properties to n-octadecane. This sensor realized in-situ detection for a solid liquid phase change, which is a significant advantage compared to the traditional phase change detection methods. A fiber heterostructure based optical fiber sensor for detection of phase changes. A single-mode-no-core-single-mode fiber optical sensor for the detection of solid-liquid and liquid-solid phase changes in n-octadecane is proposed and demonstrated. The transmission-type sensor probe consists of a short section of no-core fiber sandwiched between two sections of a single-mode fiber. The detection relies on measuring the level of the output power ratio which is caused by the large step-like variations in the RI of n-octadecane’s. Importantly, compared to the Fresnel reflection sensor, the proposed fiber heterostructure is resistant to bending and strain disturbances during the measurements. The results of this work suggest that the proposed sensor is potentially capable of detecting liquid-solid phase changes in other materials whose thermo-optic properties are similar to those of n-octadecane. Moreover, this sensor not only has the advantage of achieving in-situ phase change detection, but also has the ability of working in an environment subjected to mechanical disturbance, which makes it has great potential of industry applications. Optical fiber Fabry-Perot sensor based on a singlemode-hollow core-singlemode fiber. An optical fiber Fabry-Perot sensor to monitor the solid-liquid and liquid-solid phase changes in n-octadecane is also proposed and investigated. The sensor probe is fabricated by splicing a short section of a hollow core fiber between two single-mode fibers. By analyzing the changes in the output spectrum of the probe, such as spectral shift of a selected interference dip, the phase change within a material sample in the vicinity of the fiber probe can be accurately detected. The proposed sensor can deal with PCM types whose RI values make it difficult for the other two sensor types to work, and also can be used for detection of the material’s phase state at a particular point of its volume. This work has the potential to better understanding phase change mechanism and its application in energy engineering. Compared to the other sensors developed in the research presented in this thesis, this sensor has the advantage that the application is not limited by the RI of the PCMs

Remote Management for Multipoint Sensing Systems Using Hetero-Core Spliced Optical Fiber Sensors

This paper describes the design and experimental verification of a multipoint sensing system with hetero-core spliced optical fiber sensors and its remote management using an internet-standard protocol. The study proposes two different types of design and conducts experiments to verify those systems’ feasibility. In order to manage the sensing systems remotely, the management method uses a standard operation and maintenance protocol for internet: the Simple Network Management Protocol is proposed. The purpose of this study is to construct a multipoint sensing system remote management tool by which the system can also determine the status and the identity of fiber optic sensors. The constructed sensing systems are verified and the results have demonstrated that the first proposed system can distinguish the responses from different hetero-core spliced optical fiber sensors remotely. The second proposed system shows that data communications are performed successfully while identifying the status of hetero-core spliced optical fiber sensors remotely

Journal of Telecommunications and Information Technology, 2008, nr 1

kwartalni

Bibliography of Lewis Research Center technical publications announced in 1993

This compilation of abstracts describes and indexes the technical reporting that resulted from the scientific and engineering work performed and managed by the Lewis Research Center in 1993. All the publications were announced in the 1993 issues of STAR (Scientific and Technical Aerospace Reports) and/or IAA (International Aerospace Abstracts). Included are research reports, journal articles, conference presentations, patents and patent applications, and theses

Cardiac Arrhythmias

The most intimate mechanisms of cardiac arrhythmias are still quite unknown to scientists. Genetic studies on ionic alterations, the electrocardiographic features of cardiac rhythm and an arsenal of diagnostic tests have done more in the last five years than in all the history of cardiology. Similarly, therapy to prevent or cure such diseases is growing rapidly day by day. In this book the reader will be able to see with brighter light some of these intimate mechanisms of production, as well as cutting-edge therapies to date. Genetic studies, electrophysiological and electrocardiographyc features, ion channel alterations, heart diseases still unknown , and even the relationship between the psychic sphere and the heart have been exposed in this book. It deserves to be read