1,720,987 research outputs found
Energy Conversion at the Cuticle of Living Plants
No full textProgress towards green and autonomous energy sources includes harnessing living systems and biological tissue. It is recently discovered that the cuticle-cellular tissue bilayer in higher plant leaves functions as an integrated triboelectric generator conductor couple capable of converting mechanical stimuli into electricity. Here, it is investigated for the first time, in detail how charge generation at the living plant leaf occurs, and it is shown how whole plants could be used in plant-hybrid wind-energy harvesting systems. The charge accumulation and compensation in and ex vivo on Rhododendron leaves by Kelvin force microscopy is verified, revealing that charges are induced and transported in living plant tissue whereas charges remain unbalanced and trapped on dead leaves of the same species. A distinct sensing functionality and opportunity to upscale power output is given as electrical signals are species, touch-material, and dose-dependent and scale with frequency, impact force, and area. It is shown that also purely natural mechanical stimuli by wind or self-touching of leaves are converted into electrical signals by a triboelectric mechanism. The entirely plant-enabled and autonomous energy conversion can be used to directly drive light emitting diodes, charge a capacitor, and harvest wind-energy with promise for new energy sources based on the Plant Kingdom
Stoma-inspired valve
No full textSoft robotics and microfluidics are interdisciplinary fields with shared methods for developing
flexible and functional devices. However, manufacturing durable, efficient, and robust
devices remains a challenge. One of the key hurdles is the limited number of valve designs
available. Currently employed microvalves are either normally closed with negative control
pressure or normally open with positive control pressure. However, there has not been a
microvalve design reported which is normally closed and has positive control pressure, while
it was present for an extended period in nature in the form of a plant stoma. Plant stoma is a
robust normally closed valve with positive control pressure, with robustness arising from the
fact that when the plant dries the valve closes. It was used as an inspiration source for the
valve in this work, which is normally closed and opens at positive as well as negative control
pressure, which are improvements over previously reported designs. The findings suggest
the potential of this technology for applications ranging from artificial leaves to bioreactors.
By considering nature as an inspiration source, a contribution was made towards more sustainable
solutions
Süsinikmaterjalist elektroodidega ioonsed ja mahtuvuslikud elektroaktiivsed laminaadid sensorite ning energiakogumisseadmetena
Get PDFVäitekirja elektrooniline versioon ei sisalda publikatsioone.Kaasaegses elektroonika- ja robootikatööstuses valitseb suundumus miniatuursete, autonoomsete ja läbinisti pehmete seadmete väljatöötamisele, mis ühtlasi tingib huvi sobivate materjalide arenduse vastu. Käesolevas töös käsitletakse antud valdkonnale huvipakkuvat pehmet ioonset elektroaktiivset polümeerset laminaatmaterjali (IEAP), mis koosneb suure-eripinnalistest süsinikelektroodidest, poorsest polümeermembraanist ning ioonvedelikust, mis täidab nii elektroodi kui polümeermembraani poore. Antud laminaatmaterjal on väga multifunktsionaalne – varasemalt on tuntud selle energiasalvestus- ja täituriomadused.
Käesolevas töös uuritakse antud materjaliklassi uudset omadust – elektrilaengu genereerimise võimet. Esmalt rakendati IEAP laminaati konfiguratsioonis, mis vastab selle kasutamisele elektromehaanilise täiturina, kuid seda painutati välise jõuga. Painutamise tulemusena genereeris IEAP elektrilaengut proportsionaalselt painutuse ulatusega. Seega on võimalik sama IEAP-i kasutada vaheldumisi nii pehme täituri kui liigutussensorina.
IEAP-d iseloomustab suur tundlikkus õhuniiskuse suhtes, sest IEAP koosneb ülihügroskoopsetest koostisosadest. Elektrokeemilise impedantsspektroskoopia meetodil selgus, et õhuniiskuse pöörduva absorptsiooni tõttu võivad IEAP elektrilised omadused muutuda enam kui ühe suurusjärgu ulatuses.
Antud töös rakendati IEAP materjali kõrget niiskustundlikkust uudses, ootamatus konfiguratsioonis – hügroelektrilise rakuna. Kui IEAP paigutada kahe erineva suhtelise õhuniiskusega keskkonna eralduspiirile, tekib IEAP elektroodidel elektrilaeng. IEAP hügroelektriline rakk võimaldab koguda elektrienergiat ümbritsevast õhuniiskusest, kusjuures õhuniiskusest genereeritav elektrilaeng ületab enam kui suurusjärgu võrra painutussensorit. Siinkohal on määrava tähtsusega ka IEAP-i energiasalvestiomadused – IEAP hügroelektriline rakk ei vaja välist energiasalvestuselementi, vaid genereeritud elektrilaeng salvestatakse samasse materjaliossa, mis antud laengu genereeris.The modern electronics and robotics industry is interested in development of miniature, autonomous, and fully soft devices; consequently, the research on compatible materials is promoted. This work considers one class of materials – ionic electroactive polymer laminate (IEAP), perspective for the given field. An IEAP consists of carbonaceous electrodes with high specific surface area, a porous polymeric separator, and ionic liquid, which fills the pores in electrode and separator. IEAP is a multifunctional material – it is known for its energy storage and actuation capability.
The work at hand explores a novel property of IEAP – generation of electric charge. First, an IEAP laminate was employed in a configuration that corresponds to its use as an electromechanical actuator, but it was bent using an external force. The IEAP generated electric charge proportional to the bending magnitude. Consequently, the same IEAP could be used intermittently as a soft actuator and as a motion sensor.
IEAP consists of highly hygroscopic materials, which is expressed in its high sensitivity to ambient humidity. Electrochemical impedance spectroscopy revealed that reversible absorption of ambient humidity changes the electrical properties of IEAP over one order of magnitude.
In this work, humidity-sensitive IEAP is employed in a novel, unexpected configuration – as a hygroelectrical cell. If an IEAP is placed between environments with unequal relative humidities, electric charge is formed between the IEAP’s electrodes. An IEAP can be used to harvest electric energy from the ambient humidity, whereas the magnitude of the generated charge is more than one order of magnitude higher than in the case of the same material as a motion sensor. At this point, the energy storage properties of IEAP are essential – an IEAP hygroelectrical cell does not require additional energy storage units; instead, the generated electric charge is stored in the same part of the material, where it was generated
Self-rolling wheel using ionic elactroactive polymer actuators
Get PDFAntud töö demonstreerib Tartu Ülikooli Tehnoloogiainstituudis valmistatavate tehislihaste
unikaalseid omadusi pehmete robotite valmistamiseks. Töös kasutatud ioonne tehislihas on
oma olemuselt õhuke pehme lehekujuline laminaatmaterjal, mida saab lõigata ja vormida
sobivasse kujusse ja koostada selle täiturmaterjali abil unikaalsete omadustega ja eriliste
liikumismehhanismidega roboteid.
Töö käigus valmis ioonseid EAPsid kasutav autonoomne robot, mille edasiliikumine toimub
massikeskme nihutamise teel, kusjuures selleks ei kasutata ühtegi pöörlevat osa, peale ratta
enda tervikuna. Kogu liikumine saavutatakse roboti kuju muutmise teel. Teadaolevalt pole
varasemalt valmistatud ühtegi analoogse tööpõhimõttega robotit ioonseid tehislihaseid
kasutades.
Töös valmistati kaks roboti prototüüpi, mille kinemaatikat uuriti videotuvastuse abil. Hetkel
on roboti liikumiskiirus veel väga väike võrreldes robotitega, mis kasutavad traditsioonilisi
elektrimootoreid. See-eest on see robot üks vähestest EAP robotitest, mis suudab oma
toiteallikat ise kaasas kanda. Kindlasti suudetakse teha ka järjest paremaid aktuaatoreid, mis
parandavad roboti võimekust.
Roboti ehitamise käigus valmis elektroonikalahendus, mida on võimalik kasutada ka teiste
robotite ehitamisel IEAP aktuaatoreid kasutades. Need robotid ei pea olema veerevad.
Tulevaste robotite ehitamise juures on taaskasutatav ka töö käigus valminud
videotuvastusprogramm, mille abil on võimalik jäädvustada erinevate markerite trajektoore.
Kõik töö eesmärgid on täidetud – robot suudab iseseisvalt liikuda siledal pinnal õhu käes. Tal
on kaasas oma toiteallikas ja teda on võimalik programmeerida.The purpose of this work is to build an autonomous robot that advances using ionic
electroactive polymer actuators. The working principle of the constructed robot comprises
shift of the center of mass of a wheel-shaped robot, resulting in rolling motion. This work
demonstrates the capability of the ionic electroactive polymer actuators developed by the
Intelligent Materials and Systems Laboratory of Institute of Technology of Universty of
Tartu.
The first part of this work gives an introduction to the field of electroactive polymers. Then a
selection of previously published robots based on electroactive polymer actuators is
presented. The main part of this work starts with introduction of the concept of the robot.
Then the electrical and mechanical design of the robot is described. Two working prototypes
were made. The locomotion of the robots were analysed using video recognition
S\ufcsinikmaterjalil p\uf5hinevate kuivkontakt-elektroodide arendus ja anal\ufc\ufcs bioimpedantsi m\uf5\uf5tmiseks. Development and Analysis of Carbon-Based Dry-Contact Electrodes for Bioimpedance Measurements
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Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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