265 research outputs found
Increased Functionality Porous Optical Fiber Structures
No full textA novel fiber optic structure, termed stochastic ordered hole fibers, has been developed that contains an ordered array of six hollow tubes surrounding a hollow core, combined with a nanoporous glass creating a unique fully three dimensional pore/fiber configuration. The objective of this study is to increase the functionality of these stochastic ordered hole fibers, as well as porous clad fibers, by integrating electronic device components such as conductors, and semiconductors, and optically active materials on and in the optical fiber pore structures. Conductive copper pathways were created on/in the solid core fibers using an electroless deposition technique. A chemical vapor deposition system was built in order to attempt the deposition of silicon in on the porous clad fibers. Additionally, conductive poly(3,4-ethylenedioxythiophene)- poly(styrene sulfonate) (PEDOT:PSS) and photoactive polymer blend poly(3- hexylthiophene) and 1-(3-methoxycarbonyl)-propyl-1-phenyl-)6,6)C61 (P3HT: PCBM) were deposited on the fibers using dip coating techniques. Quantum dots of Cadmium Selenide (CdSe) with particle sizes of ranging from 2- 10 nm were deposited in the stochastic ordered hole fibers. SEM and EDS analysis confirm that copper, polymer materials, and quantum dots were deposited in the pore structure and on the surface of the fibers. Finally, resistance measurements indicate that the electrolessly deposited copper coatings have sufficient conductivity to be used as metallic contacts or resistive heating elements.Master of Scienc
Long-term stability testing of optical fibre Fabry-Perot temperature sensors
No full textApplications of fibre optic sensors at high temperatures have gained a huge interest recently, as they appeared to be suitable for temperature recording in harsh environments. In this paper, we are demonstrating two intrinsic Fabry-Perot ( F-P) fibre optic sensors for high temperature monitoring. The sensors are consisting of a 125 mu m diameter single mode fibre ( SMF28) and a 125 mu m diameter PCF ESM-12B pure fused silica fibre spliced to a SMF28, respectively. The result was a low finesse optical SMF-Cr-SMF, and SMF-Cr-PCF, sensor with cavity lengths varying from 50 mu m to 100 mu m. Both types of Fabry-Perot sensors were tested in a tube furnace over a temperature range from room temperature up to 1100 degrees C. Following a number of annealing cycles, between the above mentioned temperatures range, very good repeatability of the phase response was achieved. During the cycling process, thermal stress relief takes place which makes the sensors suitable for temperature testing at temperatures just in excess of 1000 degrees C. After initial cycling the sensors are subjected to long term stability tests. The phase response is stable, less than 4 degrees C, over a period of 5 days at a temperature of 1050 degrees C for both sensors. The temperature resolution is around 3 degrees C.</p
Design and Evaluation of Off-centered Core Fiber for Gas Sensing
No full textGas Sensing Has Become a Very Important and Attractive Technique Because of Its Various Applications, Such as in the Increasingly Concerning Case of Environmental Issues, Automobile Emission Detection, Natural Gas Leakage Detection, Etc. It Also Has Significant Applications in Industries, Such as Safety and Health Monitoring in Underground Mines. Among Those Sensing Areas, Fiber-optic Sensors Have Drawn Considerable Attention Because of Its Small Size, Light Weight, High Sensitivity, and Remote Sensing Capability. However, Current Fiber-optic Gas Sensing Techniques Have Several Limitations on Their Potential for Multiplexed or Distributed Sensing Due to Difficulties Such as High Complexity or Large Loss.
To Accomplish the Goal for Multiplexed Gas Sensing, an Off-centered Core Fiber Design Is Investigated. The Eccentric Core Can Reduce Attenuation, Keep Mechanical Strength, and Lower Fabrication Cost. To Verify the Feasibility of the Design, Fiber Field Distribution Is First Studied in Simulation, Which Will Be Discussed in Detail in Chapter 2. Then Two Fiber Samples with a Length of 10 Cm and 40 Cm Are Prepared and Placed in a Custom Methane Sensing System for Gas Absorption Testing, Which Is Detailed in Chapter 3. From Etching Analysis, Localized Surface Defects Are Found as the Main Reason for Power Loss. Performance Such as Detection Resolution and Sensitivity Are Investigated. In Chapter 4, Theoretical Evaluations Have Been Conducted for Multiplexed Sensors Performances Using the Off-centered Core Fiber to Study the Impact Fiber Parameters on Sensing System Design. The Conclusion and Summary Are Presented in Chapter 5.Master of ScienceGas Sensing Has Become a Very Important and Attractive Technique Because of Its Various Applications, Such as in the Increasingly Concerning Case of Environmental Issues, Automobile Emission Detection, Natural Gas Leakage Detection, Etc. It Also Has Significant Applications in Industries, Such as Safety and Health Monitoring in Underground Mines. Among Those Sensing Areas, Fiber-optic Sensors Have Drawn Considerable Attention Because of Its Small Size, Light Weight, High Sensitivity, and Remote Sensing Capability. However, Current Fiber-optic Gas Sensing Techniques Have Several Limitations on Their Potential for Long Distance Distributed Sensing Due to Difficulties Such as High Fabrication Complexity.
In This Work, a Fiber-optic Gas Sensor with Special Structure Was Designed. The Sensor Can Reduce Attenuation, Keep Mechanical Strength, and Lower Fabrication Cost. To Verify the Feasibility of the Design, Theory Analysis and Simulation Were Conducted, Which Will Be Discussed in Detail in Chapter 2. Then Two Samples with a Length of 10 Cm and 40 Cm Were Prepared and Placed in a Custom Methane Sensing System for Testing. And Their Performance Such as Sensitivity Is Investigated. In Chapter 4, Theoretical Evaluations Have Been Conducted for Multiplexed Sensors Performances Evaluation to Study the Impact Fiber Parameters on Sensing System Design. The Conclusion and Summary Are Presented in Chapter 5
Magnetic Sensing with Ferrofluid and Fiber Optic Connectors
No full textA simple, cost effective and sensitive fiber optic magnetic sensor fabricated with ferrofluid and commercially available fiber optic components is described in this paper. The system uses a ferrofluid infiltrated extrinsic Fabry-Perot interferometer (EFPI) interrogated with an infrared wavelength spectrometer to measure magnetic flux density. The entire sensing system was developed with commercially available components so it can be easily and economically reproduced in large quantities. The device was tested with two different ferrofluid types over a range of magnetic flux densities to verify performance. The sensors readily detected magnetic flux densities in the range of 0.5 mT to 12.0 mT with measurement sensitivities in the range of 0.3 to 2.3 nm/mT depending on ferrofluid type. Assuming a conservative wavelength resolution of 0.1 nm for state of the art EFPI detection abilities, the estimated achievable measurement resolution is on the order 0.04 mT. The inherent small size and basic structure complimented with the fabrication ease make it well-suited for a wide array of research, industrial, educational and military applications
Porous ceramic, polymer and metal materials with pores created by biological fermentation
No full textPorous polymers are made by adding biologically active agent and growth substrates (e.g., yeast and sugar, preferably in the presence of water or other suitable fluid) to a polymer forming material, which may be a liquid. The yeast acts on the sugar, forming carbon dioxide gas bubbles. The material is then polymerized so that the gas bubbles create permanent pores within the polymeric material. The polymer can be an epoxy for example. The pores will contain residue of the yeast. Also, porous metals can be made by combining a metal powder with yeast, sugar, and water. The porous metal paste is then sintered. Porous ceramics and semiconductors can be made by combining the yeast and sugar with a ceramic forming liquid such as polysilazane. Polysilazane converts to silica when heated, which helps to bind the ceramic or semiconductor powder particles at a reduced temperature. Biological agents other than yeast (e.g. bacteria, enzymes), and growth substrates other than sugar can also be used
Improving Separation of Signals from Multiple Physical Quantities Detected by Sensor Arrays
No full textModern array sensing systems, such as distributed fiber optic sensing, are used in many applications which may record a mixture of responses to multiple physical quantities. In these applications, it may be helpful to be able to separate this mixture of responses into the signals resulting from the individual sources. This is similar to the cocktail party problem posed with Independent Component Analysis (ICA), in which we use gradient ascent and fixed point iteration optimization algorithms to achieve this separation. We then seek to apply the problem setup from ICA to mixed signals resulting from a sensor array with the goal of maintaining coherence throughout resulting spatial arrays. We propose a new post-processing technique after separation to pair up the signals from different types of physical quantities based on the Symmetric Reverse Cuthill-McKee (SRCM) and Symmetric Approximate Minimum Degree (SAMD) permutations of the coherence matrix.Master of ScienceSome modern sensing systems are able to collect data resulting from different types of sources, such as vibrations and electromagnetic waves, at the same time. This means we have signals resulting from a mixture of sources. An example of one such modern sensing system is distributed fiber optic sensors used in geoscience applications, such as seismology and subsurface imaging, which measures strain along the fiber optic cable. In many applications, it may be helpful to obtain the signals from each of these sources separately, instead of having a mixture of these sources. We propose the use of optimization algorithms, in particular two algorithms arising from Independent Component Analysis (ICA), which seek to maximize a function in order to separate these signals. We then explore changes required to the algorithms for scenarios in which we have multiple sensors spaced some distance away from each other which record signals from two different sources. We also present a method of determining which separated signals correspond to which sensors after performing signal separation
Long Period Gratings in Random Hole Optical Fibers for Refractive Index Sensing
No full textWe have demonstrated the fabrication of long period gratings in random hole optical fibers. The long period gratings are fabricated by a point-by-point technique using a CO2 laser. The gratings with a periodicity of 450 µm are fabricated and a maximum coupling efficiency of −9.81 dB has been achieved. Sensing of different refractive indices in the surrounding mediums is demonstrated by applying standard liquids with refractive indices from 1.400 to 1.440 to the long period grating
Experimental Investigation of Initial Onset of Sand Deposition in the Turbine Section of Gas Turbines
No full textParticle ingestion and deposition is an issue of concern for gas turbine engines operating in harsh environments. The ingested particles accelerate the deterioration of engine components and thus reduce its service life. This effect is observed to a greater extent in aircrafts/helicopters operating in particle laden environment. Understanding the effects of particle ingestion at engine representative condition leads to improved designs for turbomachinery. Experiments have been in an Aerothermal Rig facility at Virginia Tech to study particle deposition at engine representative temperatures. The Aerothermal Rig was upgraded to achieve air temperatures of up to 1100°C at the test section. The experiments are performed using Arizona Road Dust (ARD) of 20-40 μm size range. The temperature of air and particles are around 1100°C at a constant velocity of 70 m/s. The target coupon is made of Hastelloy X, a nickel-based alloy and the angle at which the particles impact the coupon varies from 30° to 80°. The experiments were performed with different amounts of total particle injected, concentration, and coupon angle to understand their effects on deposition. Similar research was carried out in the past at the same facility to study particle deposition at temperatures up to 1050°C and 70 m/s flow velocity. However, this previous research only studied how the coupon angle affects particle deposition; other parameters such as total particle input and particle concentration were not studied. It was found that particle deposition increases significantly at higher temperatures beyond 1050°C for higher coupon angle and amount of sand injected. Results from current study also show that deposition increases with increase in total sand injected, concentration, and coupon angle for a given temperature and velocity.Master of Scienc
Structural Changes and Stability of Pore Morphologies of a Porous Glass at Elevated Temperatures
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