Optical fibers have been mostly used in fiber optic communications, imaging optics, sensing technology, etc. Fiber optic sensors have gained increasing attention for scientific and structural health monitoring (SHM) applications. In this study, fiber loop ringdown (FLRD) sensors were fabricated for scientific, SHM, and sensor networking applications. FLRD biosensors were fabricated for both bulk refractive index (RI)- and surface RI-based DNA sensing and one type of bacteria sensing. Furthermore, the effect of glucose oxidase (GOD) immobilization at the sensor head on sensor performance was evaluated for both glucose and synthetic urine solutions with glucose concentration between 0.1% and 10%. Detection sensitivities of the glucose sensors were achieved as low as 0.05%. For chemical sensing, heavy water, ranging from 97% to 10%, and several elemental solutions were monitored by using the FLRD chemical sensors. Bulk indexbased FLRD sensing showed that trace elements can be detected in deionized water. For physical sensing, water and cracking sensors were fabricated and embedded into concrete. A partially-etched single-mode fiber (SMF) was embedded into a concrete bar for water monitoring while a bare SMF without any treatment was directly embedded into another concrete bar for monitoring cracks. Furthermore, detection sensitivities of water and crack sensors were investigated as 10 ml water and 0.5 mm surface crack width, respectively Additionally fiber loop ringdowniber Bragg grating temperature sensors were developed in the laboratory; two sensor units for water, crack, and temperature sensing were deployed into a concrete cube in a US Department of Energy test bed (Miami, FL). Multi-sensor applications in a real concrete structure were accomplished by testing the six FLRD sensors. As a final stage, a sensor network was assembled by multiplexing two or three FLRD sensors in series and parallel. Additionally, two FLRD sensors were combined in series and parallel by using a 2×1 micro-electromechanical system optical switch to control sensors individually. For both configurations, contributions of each sensor to two or three coupled signals were simulated theoretically. Results show that numerous FLRD sensors can be connected in different configurations, and a sensor network can be built up for multiunction sensing applications.

Wireless sensor networks (WSNs) is a virtual layer in the paradigm of the Internet of Things (IoT). It inter-relates information associated with the physical domain to the IoT drove computational systems. WSN provides an ubiquitous access to location, the status of different entities of the environment, and data acquisition for long-term IoT monitoring. Since energy is a major constraint in the design process of a WSN, recent advances have led to project various energy-efficient protocols. Routing of data involves energy expenditure in considerable amount. In recent times, various heuristic clustering protocols have been discussed to solve the purpose. This article is an improvement of the existing stable election protocol (SEP) that implements a threshold-based cluster head (CH) selection for a heterogeneous network. The threshold maintains uniform energy distribution between member and CH nodes. The sensor nodes are also categorized into three different types called normal, intermediate, and advanced depending on the initial energy supply to distribute the network load evenly. The simulation result shows that the proposed scheme outperforms SEP and DEEC protocols with an improvement of 300% in network lifetime and 56% in throughput.

The Global Positioning System (GPS) provides good precision on a global scale, but is not suitable for indoor applications. Indoor positioning systems (IPS) aim to provide high precision position information in an indoor environment. IPS has huge market opportunity with a growing number of commercial and consumer applications especially as Internet of Things (IoT) develops. This paper studies an IPS approach using audible sound and pseudo-noise (PN) based time difference of arrival (TDoA). The system’s infrastructure consists of synchronized speakers. The object to be located, or receiver, extracts TDoA information and uses multilateration to calculate its position. The proposed IPS utilizes sound waves since they travel much slower compared to electromagnetic waves, allowing for easier measurements. Additionally, the audible spectrum has a large availability of low directivity speakers and microphones allowing for a large coverage area compared to highly directive ultrasonic transceivers. This paper experimentally evaluates the feasibility of the proposed IPS.

Wireless sensor networks (WSNs) have been a topic of research for decades. Researchers have been exploring different uses for UAVs with their growing popularity. In this thesis I develop a wireless sensor network (WSN) and introduce the theoretical effects of an unmanned aerial vehicle (UAV) for wireless recharging of individual nodes in the WSN. My research focuses on understanding how to use wireless recharging technology to maximize the lifetime of a WSN by simulating recharging on the physical nodes. Using a three by three grid of nine sensor nodes, I proved that recharging the lowest powered node in the network at each sink iteration increased the lifetime of the WSN by 538% when compared to no recharging. I also further investigate the potential uses of a WSN and UAV for detecting and deterring animals. Using wireless sensor nodes to initially detect movement, and the UAV to find the object proved to be a viable solution for offloading the more power intensive tasks from the WSN to the UAV.

Since dangerous goods have special physical and chemical properties, they can easily produce explosion, fire, poisoning and other accident due to a traffic collision or hazardous leak under a complex transport condition. Compared with ordinary traffic accidents, accident of dangerous goods transportation has greater risks and subsequent influence. Due to the huge transportation equipment and high freight volumes, once the accident occurred, it will be difficult to deal with the danger in the first place. Faced with such a grim situation, this paper develops a system to achieve real- time monitoring of dangerous goods transportation based on wireless sensor network (WSN). Combined with different kind of sensors, wireless communication technology and data fusion technology, a real-time monitor system is developed for dangerous good transportation. In addition to real- time monitoring, the system can analyze the state parameters obtained to check whether the vehicle is in a safe condition. The system has a real-time tracking, monitoring and early warning function which has important significance in curbing accidents and lowering the accident loss as far as possible

Yes / Underwater communication applications extensively use localization services for object identification. Because of their significant impact on ocean exploration and monitoring, underwater wireless sensor networks (UWSN) are becoming increasingly popular, and acoustic communications have largely overtaken radio frequency (RF) broadcasts as the dominant means of communication. The two localization methods that are most frequently employed are those that estimate the angle of arrival (AOA) and the time difference of arrival (TDoA). The military and civilian sectors rely heavily on UWSN for object identification in the underwater environment. As a result, there is a need in UWSN for an accurate localization technique that accounts for dynamic nature of the underwater environment. Time and position data are the two key parameters to accurately define the position of an object. Moreover, due to climate change there is now a need to constrain energy consumption by UWSN to limit carbon emission to meet net-zero target by 2050. To meet these challenges, we have developed an efficient localization algorithm for determining an object position based on the angle and distance of arrival of beacon signals. We have considered the factors like sensor nodes not being in time sync with each other and the fact that the speed of sound varies in water. Our simulation results show that the proposed approach can achieve great localization accuracy while accounting for temporal synchronization inaccuracies. When compared to existing localization approaches, the mean estimation error (MEE) and energy consumption figures, the proposed approach outperforms them. The MEEs is shown to vary between 84.2154m and 93.8275m for four trials, 61.2256m and 92.7956m for eight trials, and 42.6584m and 119.5228m for twelve trials. Comparatively, the distance-based measurements show higher accuracy than the angle-based measurements.

Anthropogenic activity has caused increased concentrations of greenhouse gases (GHGs) in the atmosphere which has resulted in global warming gaining momentum. GHG emission estimates up to date are insufficient and in order to mitigate GHG emissions of anthropogenic origin fluxes of GHGs need to be mapped. The application of low-cost sensors (LCSs) as an environmental monitoring tool has been seen as a pathway with the ability to provide GHG estimates that can help us to identify sources and sinks. However, questions have been highlighted regarding the accuracy of LCSs in targeting GHGs in comparison to alternative environmental monitoring approaches. A network of LCSs with the ability to target carbon dioxide (CO2) and methane (CH4), among other environmental parameters of interest, were deployed at a wastewater treatment plant (WWTP) in Linköping, Sweden. A cross-checking procedure where LCS data were compared with data from high-precision measuring instruments UltraPortable Greenhouse Gas Analyser (UGGA) and air samples analysed with gas chromatography (GC), enabled evaluation of LCSs as an environmental monitoring tool. Despite uncertainties regarding individual sensors´ behaviour, results from this study show that LCS systems have the capability to bring valuable estimates of GHGs to the environmental monitoring field, although not yet at the precise level of reference equipment. The low cost of the LCS systems studied in this work open a range of possibilities because of their ability to provide large amounts of data on both a spatial and temporal scale that are not attainable for high-precision reference instruments. From the long-term measurements it can be concluded that the CO2 concentrations at the dewatered sludge deposit, and especially inside the screw conveyor building, are higher than global average levels of CO2. / Mänsklig aktivitet har orsakat ökade koncentrationer av växthusgaser i atmosfären vilket i sin tur har resulterat i att den globala uppvärmningen har accelererat. Estimeringar av växthusgasutsläpp har hittills varit bristfälliga och för att kunna lindra antropogena växthusgasutsläpp kartläggning av växthusgasers utbyten efterfrågas. Applicering av lågkostnads-sensorer som en ett verktyg inom miljöövervakning har setts som en möjlig väg i att tillhandahålla estimeringar av växthusgaser som kan hjälpa oss att identifiera källor och sänkor. Dock har frågor om hur precisa lågkostnads-sensorer är i jämförelse med alternativa miljöövervakningsmetoder lyfts. Ett nätverk av låg kostnads-sensorer som kan känna av koldioxid (CO2) and metan (CH4) och en rad andra miljömässiga parametrar av intresse, placerades ut på ett reningsverk i Linköping, Sverige. En procedur där sensordata ställdes mot data insamlad från de högprecisa instrumenten Ultra-Portable Greenhouse Gas Analyser och luftprover analyserande med gas kromatografi öppnade upp för möjligheten att utvärdera sensorernas prestanda. Trots osäkerheter i data gällande individuella sensorers beteende, så visar resultat från den här studien att låg kostnads-sensorsystem har kapaciteten att bidra med berikande estimeringar av växthusgaser till miljöövervakning området, dock ännu inte med samma precishet som för referensinstrument. Den låga kostnaden för lågkostnads-sensorsystemen som studeras i det här arbetet öppnar upp för en rad möjligheter tack vare att de kan tillhandahålla stora mängder data på både en spatial och temporal skala som inte är inom räckhåll för högprecisa referensinstrument. Från långtidsmätningarna kan det konstateras att koncentrationerna av CO2 vid slamavvattningslagret, och särskilt inne i skruvpressbyggnaden, är högre än det globala genomsnittsvärden för CO2 nivåer.

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