Dynamic Adaptive Real-Time Particle Image Velocimetry

Thesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2013.Cataloged from PDF version of thesis.Includes bibliographical references (pages 65-67).Particle Image Velocimetry (PIV) is a technique that allows for the detailed visualization of fluid flow. By performing computational analysis on images taken by a high-sensitivity camera that monitors the movement of laser-illuminated tracer particles over time, PIV is capable of producing a vector field describing instantaneous velocity measurements of the fluid captured in the field of view. Nearly all PIV implementations perform offline processing of the collected data, a feature that limits the scope of the applications of this technique. Recently, however, researchers have begun to explore the possibility of using FPGAs or PCs to greatly improve the efficiency of these algorithms in order to obtain real-time speeds for use in feedback loops. Such approaches are very promising and can help expand the use of PIV into previously unexplored fields, such as high performance Unmanned Aerial Vehicles (UAVs). Yet these real-time algorithms have the potential to be improved even further. This thesis outlines an approach to make real-time PIV algorithms more accurate and versatile in large part by applying principles from another emerging technique called adaptive PIV, and in doing so will also address new issues created from the conversion of traditional PIV to a real-time context. This thesis also documents the implementation of this Dynamic Adaptive Real- Time PIV (DARTPIV) algorithm on a PC with CUDA parallel computing, and its performance and results analyzed in the context of normal real-time PIV.by Samvaran Sharma.M. Eng

Real-Time Background Oriented Schlieren: Catching Up With Knife Edge Schlieren

Background Oriented Schlieren (BOS) is a widely used technique that provides density gradient information in flow fields of interest, without imposing stringent optical quality requirements on the facility/experiment windows and/or optics used in the BOS setup. Typically, the BOS reference image is acquired before the test begins (flow off) and then the "live" image data are acquired during the actual testing/experiment (flow on). The raw BOS image data, while displayed in real-time as they are acquired from the camera, unfortunately provide little if any visual indication of the density gradients in the flow. Generally, the "live" images must be processed off-line after the testing is completed, providing no indication of the success of the BOS setup and no feedback on the operational success of the test. Advances in computer processing hardware enables the implementation of real-time processing and display of the BOS image data. Two different approaches to implementing the real-time BOS (RT-BOS) processing capability are described herein. First, a traditional multi-core Central Processing Unit (CPU) based approach using scheduled parallel threads is used to build a RT-BOS processing engine. In the second approach, a Graphical Processing Unit (GPU) approach is used to costruct a RT-BOS processing engine. Generally, high core count CPU processors can provide a useful processing rate for RT-BOS. However, the GPU based approach exceeds the processing capability of the CPU approach, at a fraction of the cost. The GPU approach places no restrictions on the Host PC processing capability, except that it be capable of acquiring the BOS image data from the camera in real-time

Dual beam swept source optical coherence tomography for microfluidic velocity measurements

Microfluidic flows are an increasing area of interest used for “lab-on-a-chip” bioanalytical techniques, drug discovery, and chemical processing. This requires optical, non-invasive flow-visualization techniques for characterising microfluidic flows. Optical Coherence Tomography (OCT) systems can provide three-dimensional imaging through reasonably-opaque materials with micrometre resolution, coupled to a single optical axis point using optical fibre cables. Developed for imaging the human eye, OCT has been used for the detection of skin cancers and endoscopically in the human body. Industrial applications are growing in popularity including for the monitoring of bond-curing in aerospace, for production-line non-destructive-testing, and for medical device manufacturing and drug encapsulation monitoring. A dual beam Optical Coherence Tomography system has been developed capable of simultaneously imaging microfluidic channel structures, and tracking particles seeded into the flow to measure high velocity flows, using only a single optical access point. This is achieved via a dual optical fibre bundle for light delivery to the sample and a custom high-speed dual channel OCT instrument using an akinetic sweep wavelength laser. The system has 10 μm resolution in air and a sweeping rate of 96 kHz. This OCT system was used to monitor microfluidic flows in 800 μm deep test chips and Poiseuille flows were observed

Simultaneous in situ characterisation of bubble dynamics and a spatially resolved concentration profile : A combined Mach-Zehnder holography and confocal Raman-spectroscopy sensor system

For a reaction between a gaseous phase and a liquid phase, the interaction between the hydrodynamic conditions, mass transport and reaction kinetics plays a crucial role with respect to the conversion and selectivity of the process. Within this work, a sensor system was developed to simultaneously characterise the bubble dynamics and the localised concentration measurement around the bubbles. The sensor system is a combination of a digital Mach-Zehnder holography subsystem to measure bubble dynamics and a confocal Raman-spectroscopy subsystem to measure localised concentration. The combined system was used to investigate the chemical absorption of CO₂ bubbles in caustic soda in microchannels. The proposed set-up is explained and characterised in detail and the experimental results are presented, illustrating the capability of the sensor system to simultaneously measure the localised concentration of the carbonate ion with a good limit of detection and the 3-D position of the bubble with respect to the spot where the concentration was measured

Noninvasive Thrombolysis using Microtripsy

Thrombosis refers to blood clot formation and when pathological, is the cause of many vascular diseases. For example, deep vein thrombosis (DVT), which affects three million Americans per year, is the formation of clots in the deep veins of the legs. Current clinical treatments include thrombolytic drugs and catheter-based surgical procedures. Both methods have significant drawbacks, such as excessive bleeding, invasiveness, and long treatment time. Ultrasound has been combined with thrombolytic drugs and/or microbubbles to enhance drug delivery. However, these methods are still quite slow and share the drawbacks of thrombolytic drugs. Histotripsy is a tissue ablation method that mechanically fractionates soft tissue via well-controlled acoustic cavitation generated by microsecond-long, high-pressure ultrasound pulses. The initial feasibility and safety of using histotripsy as a noninvasive, drug-free, and image-guided thrombolysis technique has been demonstrated both in vitro and in vivo. The overriding goal of this dissertation is clinical translation of histotripsy thrombolysis. First, an integrated image-guided histotripsy thrombolysis system suitable for clinical DVT treatment are designed and constructed. Second, the recently discovered technical innovations, microtripsy and bubble-induced color Doppler (BCD), are investigated for histotripsy thrombolysis application to further improve treatment efficacy. Microtripsy is a new histotripsy approach and uses an intrinsic threshold mechanism to generate more reproducible and predictable cavitation via a single ultrasound pulse, which can minimize vessel damage by confining cavitation within vessel lumen and eliminate cavitation on vessel wall. BCD is developed to monitor tissue motion induced by histotripsy pulses and investigated as a real-time quantitative feedback for histotripsy thrombolysis. Finally, a comprehensive pre-clinical study in a large animal DVT model is conducted to validate the safety and efficacy of this clinically designed system incorporating these technical innovations. It is our hope that this dissertation work will establish a foundation for the translation of this noninvasive thrombolysis technology into relevant clinical applications.PHDBiomedical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/135813/1/xizh_1.pd

Advanced Applications of Rapid Prototyping Technology in Modern Engineering

Rapid prototyping (RP) technology has been widely known and appreciated due to its flexible and customized manufacturing capabilities. The widely studied RP techniques include stereolithography apparatus (SLA), selective laser sintering (SLS), three-dimensional printing (3DP), fused deposition modeling (FDM), 3D plotting, solid ground curing (SGC), multiphase jet solidification (MJS), laminated object manufacturing (LOM). Different techniques are associated with different materials and/or processing principles and thus are devoted to specific applications. RP technology has no longer been only for prototype building rather has been extended for real industrial manufacturing solutions. Today, the RP technology has contributed to almost all engineering areas that include mechanical, materials, industrial, aerospace, electrical and most recently biomedical engineering. This book aims to present the advanced development of RP technologies in various engineering areas as the solutions to the real world engineering problems

A Single Photon Avalanche Diode Array Fabricated in 0.35um CMOS and based on an Event-Driven Readout for TCSPC Experiments

The design and characterization of an imaging sensor based on single photon avalanche diodes is presented. The sensor was fully integrated in a 0.35µm CMOS technology. The core of the imager is an array of 4x112 pixels that independently and simultaneously detect the arrival time of photons with picosecond accuracy. A novel event-driven readout scheme allows parallel column-wise and non-sequential, on-demand row-wise operation. Both time-correlated and time-uncorrelated measurements are supported in the sensor. The readout scheme is scalable and requires only 11 transistors per pixel with a pitch of 25µm. A number of standard performance measurements for the imager are presented in the paper. An average dark count rate of 6Hz and 750Hz are reported at room temperature respectively for an active area diameter of 4µm and 10µm, while the dead time is 40ns with negligible crosstalk. A timing resolution better than 80ps over the entire integrated array makes this technique ideal for a fully integrated high resolution streak camera, thus enabling fast TCSPC experiments. Applications requiring low noise, picosecond timing accuracies, and measurement parallelism are prime candidates for this technology. Examples of such applications include bioimaging at cellular and molecular level based on fluorescence lifetime imaging and/or, fluorescence correlation spectroscopy, as well as fast optical imaging, optical rangefinders, LIDAR, and low light level imagers