A Lightweight Hyperspectral Imager

Tässä työssä suunniteltiin ja toteutettiin ohjauselektroniikka hyperspektrikameraa varten. Hyperspektrikamera on spektrometri, jolla voidaan mitata spektri jokaiselle kuvan pikselille. Työssä käytetyn hyperspektraalisen kameran toiminta perustuu Fabry-Perot-interferometrin päästökaistojen ja värikuvasensorin pikseleiden toisistaan eroavien herkkyyksien hyödyntämiseen. Ohjaamalla interferometrin päästökaistoja sopivasti voidaan kuvasensorin eri pikseleiden avulla selvittää yhdestä kuvasta jopa kolmen spektrikaistan sisältö. Tutkittava spektrialue voidaan mitata muuttamalla transmissiokaistoja perättäisten kuvien välillä. Toteutettu hyperspektraalinen kamera tarvitsee menetelmän, jolla interferometrin peilejä voidaan ohjata tarkasti. Interferometrin peilien välistä ilmarakoa tuli ohjata nanometrin tarkkuudella 600 nm - 3000 nm alueella. Työssä hyödynnettiin Fabry-Perot-interferometria, jonka ilmarakoa ohjataan kolmen pietsosähköisen aktuaattorin avulla. Interferometrin ilmarakoa mitataan kapasitiivisesti kolmesta kohdasta, mikä mahdollistaa takaisinkytketyn säädön toteuttamisen. Lisäksi aiemmin VTT:llä kehitettyyn kuvauselektroniikkaan lisättiin flash-muisti hyperspektraalisen tiedon tallentamiseksi. Toteutetun hyperspektraalisen kameran tehon kulutus on vain 1.6 W. Kameran paino on noin 350 g. Työssä mitattiin myös interferometrin ja ohjauselektroniikan suorituskykyä. Interferometrin ilmaraon asettumisaika 200 nm askelmaiselle muutokselle on noin 0.6 ms. Kohinan aiheuttamaa ilmaraon muutosta arvioitiin mittaamalla kohina virhesignaalin esivahvistimen lähdössä ja laskemalla tätä kohinajännitettä vastaava ilmaraon muutos. Tämän arvioitiin olevan tehollisarvoltaan noin 0.1 nm. Ympäristön vaikutusten todettiin aiheuttavan suurimmat ongelmat ilmaraon ohjauksen tarkkuudessa. Varsinkin lämpötila ja kosteus vaikuttavat ohjauksen tarkkuuteen ja säätöalueeseen. Kosteus muuttaa lähinnä säätöaluetta, mutta lämpötila vaikuttaa myös ilmaraon asetusarvojen tarkkuuteen. Lämpötilan todettiin muuttavan ilmarakoa enimmillään 0.5 nm/°C.In this work a control platform was designed for a hyperspectral imager. A hyperspectral imager is a spectrometer that can be used to obtain spectral data for each pixel in the image. The hyperspectral imager concept used in this work utilizes multiple transmission orders of a Fabry-Perot interferometer together with the different spectral sensitivities of RGB-image sensor pixels. With the built hyperspectral imager it is possible to acquire 2D spatial images at one, two or three selected wavelength bands simultaneously. By adjusting the transmission bands of the Fabry-Perot interferometer it is possible to measure the reflectance spectrum of the observed area. The hyperspectral imager requires an accurate control mechanism for the interferometer mirrors as the air gap is controlled over a range of 600 nm to 3000 nm with one nanometre accuracy. The interferometer module used in this work is controlled with three piezoelectric actuators and the air gap is measured near each actuator to provide position information for the control system. A three channel closedloop control system was designed and built for the interferometer module to control the parallelism and spacing between the mirror plates. A previous imaging system was modified to accommodate a flash memory which is used for saving the hyperspectral data. The power consumption of the imager was measured to be 1.6 W and the total mass of the imager including the battery is 350 g. Several measurements were made to provide information on the system performance. The settling time for a 200 nm step change in the air gap was measured to be 0.6 ms. The noise induced air gap variation was estimated from the noise in the amplified error signal. The root-mean-square value of this movement was approximately 0.1 nm. The performance of the air gap control is decreased by the changes in the environment. The humidity of the environment changes the useful control range of the air gap. Temperature changed the air gap approximately 0.5 nm/°C

Development, Optimization and Clinical Evaluation Of Algorithms For Ultrasound Data Analysis Used In Selected Medical Applications.

The assessment of soft and hard tissues is critical when selecting appropriate protocols for restorative and regenerative therapy in the field of dental surgery. The chosen treatment methodology will have significant ramifications on healing time, success rate and overall long-time oral health. Currently used diagnostic methods are limited to visual and invasive assessments; they are often user-dependent, inaccurate and result in misinterpretation. As such, the clinical need has been identified for objective tissue characterization, and the proposed novel ultrasound-based approach was designed to address the identified need. The device prototype consists of a miniaturized probe with a specifically designed ultrasonic transducer, electronics responsible for signal generation and acquisition, as well as an optimized signal processing algorithm required for data analysis. An algorithm where signals are being processed and features extracted in real-time has been implemented and studied. An in-depth algorithm performance study has been presented on synthetic signals. Further, in-vitro laboratory experiments were performed using the developed device with the algorithm implemented in software on animal-based samples. Results validated the capabilities of the new system to reproduce gingival assessment rapidly and effectively. The developed device has met clinical usability requirements for effectiveness and performance

Video guidance, landing, and imaging systems

The adaptive potential of video guidance technology for earth orbital and interplanetary missions was explored. The application of video acquisition, pointing, tracking, and navigation technology was considered to three primary missions: planetary landing, earth resources satellite, and spacecraft rendezvous and docking. It was found that an imaging system can be mechanized to provide a spacecraft or satellite with a considerable amount of adaptability with respect to its environment. It also provides a level of autonomy essential to many future missions and enhances their data gathering ability. The feasibility of an autonomous video guidance system capable of observing a planetary surface during terminal descent and selecting the most acceptable landing site was successfully demonstrated in the laboratory. The techniques developed for acquisition, pointing, and tracking show promise for recognizing and tracking coastlines, rivers, and other constituents of interest. Routines were written and checked for rendezvous, docking, and station-keeping functions

Functional regeneration of glossopharyngeal nerve through micromachined sieve electrode arrays

To assess the potential of micromachined silicon sieve electrodes for long term recording from single afferent sensory fibers, we implanted them between the cut ends of rat glossopharyngeal nerves which innervate taste and somatosensory receptors on the posterior tongue. After the implants had been in place for an average of 101 days nerve regeneration was measured using histological and electrophysiological methods. Axons of the glossopharyngeal nerve regenerated through holes in the sieves and supported the functional regeneration of taste, thermal and mechanoreceptors.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/29783/1/0000122.pd

Silicon nanoparticles with a polymer-derived carbon shell for improved lithium-ion batteries: Investigation into volume expansion, gas evolution, and particle fracture

Silicon (Si) and composites thereof, preferably with carbon (C), show favorable lithium (Li) storage properties at low potential, and thus hold promise for application as anode active materials in the energy storage area. However, the high theoretical specific capacity of Si afforded by the alloying reaction with Li involves many challenges. In this article, we report the preparation of small-size Si particles with a turbostratic carbon shell from a polymer precoated powder material. Galvanostatic charge/discharge experiments conducted on electrodes with practical loadings resulted in much improved capacity retention and kinetics for the Si/C composite particles compared to physical mixtures of pristine Si particles and carbon black, emphasizing the positive effect that the core−shell-type morphology has on the cycling performance. Using in situ differential electrochemical mass spectrometry, pressure, and acoustic emission measurements, we gain insights into the gassing behavior, the bulk volume expansion, and the mechanical degradation of the Si/C composite-containing electrodes. Taken together, our research data demonstrate that some of the problems of high-content Si anodes can be mitigated by carbon coating. Nonetheless, continuous electrolyte decomposition, particle fracture, and electrode restructuring due to the large volume changes during battery operation (here, ∼170% in the voltage range of 600−30 mV vs Li+/Li) remain as serious hurdles toward practical implementation

Electronic bidirectional interfaces to the peripheral nervous system for prosthetic applications

The research presented in this thesis concerns the field of bioelectronics, in particular the work has been focused on the development of special electronic devices for neural signal acquisition and Peripheral Nervous System (PNS) stimulation. The final aim of the project in which this work is involved is in fact the realization of a prosthetic hand controlled using neural signals. The commercially available prosthesis are based on Electromyographic (EMG) signals, their use implies unnatural movements for the patient that needs a special training to develop the control capabilities over the mechanical limb. The proposed approach offers a number of advantages compared to the traditional prosthesis, first because the signals used are the same used to control the biologic limb, allowing a more comfortable solution for the patient that gets closer to feel the robotic hand as a natural extension of his/her body. Secondly, placing temperature and pressure sensors on the limb surface, it is possible to trasduce such information in an electrical current that, injected into the PNS, can restore the sensory feedback in amputees. The final goal of this research is the development of a fully implantable device able to perform a bidirectional communication between the robotic hand and the patient. Due to small area, low noise and low power constraints, the only possible way to reach this aim is the design of a full custom Integrated Circuit (IC). However a preliminary evaluation of the key design features, such as neural signal amplitudes and frequencies as well as stimulation shape parameters, is necessary in order to define clearly and precisely the design specifications. A low-cost and short implementation time device is then needed for this aim, the Components Off The Shelf (COTS) approach seems to be the best solution for this purpose. A Printed Circuit Board (PCB) with discrete components has been designed, developed and tested, the information extracted by the test results have been used to guide the IC design. The generation of electrical signals in biological cells, such as neural spikes, is possible thanks to ions that move across the cell membrane. In many applications it is important, not only to record the spikes, but also to measure these small currents in order to understand which electro-chemical processes are involved in the signal generation and to have a direct measurement of the ion channels involved in the reaction. Ion currents, in fact, play a key role in several physiological processes, in neural signal generation, but also in the maintenance of heartbeat and in muscle contraction. For this purpose, a system level implementation of a Read out circuit for ion channel current detection has been developed

Towards Practical Triboelectric Nanogenerator for Mechanical Energy Harvesting and Self-powered Sensing

Triboelectric nanogenerator (TENG) offers a promising solution as a decentralised energy source to sustainably power the ever-growing mobile electronics. TENG’s characteristics such as high output, versatile working modes and broad material availability have made it viable but still there are a few issues that limit practical applications of TENG. This thesis aims to tackle some of the practical limitations of TENGs to be used as wearable energy harvesters or self-powered sensors. Firstly, to address the poor stretchability of TENG with rigid metal / carbon electrodes for wearable applications, a soft and highly stretchable solid polymer electrode (SPE) based on biocompatible PVA infused with ionically conductive ingredient was developed as the TENG electrode. The use of SPE endows the TENG with high stretchability, superb transparency, environmental stability, and enhanced electrical output. Then the requirement of complex power management system of conventional TENG with AC output was simplified with a new design of DC-TENG boosted by a dual-breakdown mechanism. The DC output could be directly utilized by small electronics without the need of rectifiers, thus reducing complexity and energy loss. Lastly, for TENG-based sensors, to overcome the errors caused by TENG output variations under changing environment, a new method of extracting sensing signals independent of intrinsic TENG output variations is proposed. This research has yielded several important scientific contributions in the device design, optimisation and application of TENG. These findings provide new opportunities to improve TENGs in terms of wearing comfort, system complexity and sensing reliability, thus greatly enhancing the practical application of TENGs in real-life scenarios

Technology applications

A summary of NASA Technology Utilization programs for the period of 1 December 1971 through 31 May 1972 is presented. An abbreviated description of the overall Technology Utilization Applications Program is provided as a background for the specific applications examples. Subjects discussed are in the broad headings of: (1) cancer, (2) cardiovascular disease, (2) medical instrumentation, (4) urinary system disorders, (5) rehabilitation medicine, (6) air and water pollution, (7) housing and urban construction, (8) fire safety, (9) law enforcement and criminalistics, (10) transportation, and (11) mine safety

Advanced sensors technology survey

This project assesses the state-of-the-art in advanced or 'smart' sensors technology for NASA Life Sciences research applications with an emphasis on those sensors with potential applications on the space station freedom (SSF). The objectives are: (1) to conduct literature reviews on relevant advanced sensor technology; (2) to interview various scientists and engineers in industry, academia, and government who are knowledgeable on this topic; (3) to provide viewpoints and opinions regarding the potential applications of this technology on the SSF; and (4) to provide summary charts of relevant technologies and centers where these technologies are being developed